Biosensors

15 pages, 4932 KiB

Open AccessArticle

Analysis of Mn²⁺ and Zn²⁺ Ions in Macroalgae with Heteroelement-Doped Carbon-Based Fluorescent Probe

by Hui Xu, Xin You, Yue Lu, Peng Liang, Zhihui Luo, Yiwei Wang, Shaoxiao Zeng and Hongliang Zeng

Biosensors 2022, 12(5), 359; https://doi.org/10.3390/bios12050359 - 22 May 2022

Cited by 3 | Viewed by 2709

Abstract

Kelp and laver are large economic macroalgae in China, which are rich in nutrients, especially Mn and Zn. Excessive intake of Mn and Zn can be harmful to the human body. Therefore, it is necessary to develop a convenient and efficient method to [...] Read more.

Kelp and laver are large economic macroalgae in China, which are rich in nutrients, especially Mn and Zn. Excessive intake of Mn and Zn can be harmful to the human body. Therefore, it is necessary to develop a convenient and efficient method to detect the contents of Mn and Zn in macroalgae. In this experiment, red carbon dots (R-CDs) doped with N and S elements were prepared by the thermal solvent method. The obtained R-CDs displayed excitation wavelength-independent fluorescent emission in the red spectral region. The R-CDs were used to construct a fluorescent probe for specific recognition of Mn²⁺ and Zn²⁺, achieving high-sensitivity detection of Mn²⁺ and Zn²⁺. The detection results showed a good linear relationship between fluorescence intensity and Mn²⁺ concentration, and the calculated detection limit was 0.23 nmol/L. For the detection of Zn²⁺, the detection limit was estimated as 19.1 nmol/L. At the same time, the content distribution of Mn and Zn elements in macroalgae produced in Fujian was investigated by the constructed fluorescence probe. It was found that kelp, laver, and their products are rich in Mn and Zn elements, and the content of Mn and Zn elements in laver is higher than that in kelp, which can be used as the optimal food supplement for Mn and Zn elements. Full article

(This article belongs to the Special Issue Smart and Multifunctional Nanomaterials and Applications for Food Safety)

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UV–visible absorption spectrum (blue), excitation spectrum (red), and emission spectrum (black) of R-CDs (A); fluorescence emission spectra of R-CDs (B). Full article ">Figure 2
TEM (A) and HRTEM images (B) of R-CDs. Full article ">Figure 3
XRD (A) and FT-IR spectra of R-CDs (B). Full article ">Figure 4
Schematic illustration of the preparation of R-CDs and the application in the detection of Mn2+ and Zn2+ (A). Fluorescence spectra of R-CDs (black curve) and R-CDs+Mn2+ (red curve) (B). Fluorescence spectra of R-CDs (black curve) and R-CDs+Zn2+ (red curve) (C). Full article ">Figure 5
Fluorescence responses of the R-CDs upon the addition of different concentrations of Mn2+ (A) and the linear correlation of fluorescence intensity versus the concentrations of Mn2+ in the range from 0 ng/mL to 100 ng/mL (B). Full article ">Figure 6
Specificity of the fluorescence probe for Mn2+ analysis. Full article ">Figure 7
Fluorescence responses in the λEm = 650 nm of the R-CDs upon the addition of different concentrations of Zn2+ (A) and linear correlation of fluorescence intensity versus the concentrations of Zn2+ in the range from 1 ng/mL to 50 ng/mL (B). Full article ">Figure 8
Specificity of the fluorescence probe for sensing Zn2+. Full article ">

11 pages, 2510 KiB

Open AccessArticle

Energy-Efficient, On-Demand Activation of Biosensor Arrays for Long-Term Continuous Health Monitoring

by Jonathan Lundquist, Benjamin Horstmann, Dmitry Pestov, Umit Ozgur, Vitaliy Avrutin and Erdem Topsakal

Biosensors 2022, 12(5), 358; https://doi.org/10.3390/bios12050358 - 21 May 2022

Cited by 4 | Viewed by 2736

Abstract

Wearable biosensors for continuous health monitoring, particularly those used for glucose detection, have a limited operational lifetime due to biodegradation and fouling. As a result, patients must change sensors frequently, increasing cost and patient discomfort. Arrays of multiple sensors, where the individual devices [...] Read more.

Wearable biosensors for continuous health monitoring, particularly those used for glucose detection, have a limited operational lifetime due to biodegradation and fouling. As a result, patients must change sensors frequently, increasing cost and patient discomfort. Arrays of multiple sensors, where the individual devices can be activated on demand, increase overall operational longevity, thereby reducing cost and improving patient outcomes. This work demonstrates the feasibility of this approach via decomposition of combustible nitrocellulose membranes that protect the individual sensors from exposure to bioanalytes using a current pulse. Metal contacts, connected by graphene-loaded PEDOT:PSS polymer on the surface of the membrane, deliver the required energy to decompose the membrane. Nitrocellulose membranes with a thickness of less than 1 µm consistently transfer on to polydimethylsiloxane (PDMS) wells. An electrical energy as low as 68 mJ has been shown to suffice for membrane decomposition. Full article

(This article belongs to the Special Issue Device-on-Chip Application in Biomedical Engineering)

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Nitrocellulose membrane and spin-coating data. (a) Nitrocellulose spin-coating curves for different solution weight/volume (w/v) ratios [<a href="#B36-biosensors-12-00358" class="html-bibr">36</a>]. (b) Nitrocellulose membrane thickness profile for Wafer 1 (6-inch wafer) and Wafer 2 (3-inch wafer). Full article ">Figure 2
Graphene-loaded polymer filament structure. Full article ">Figure 3
Pulse current circuit. Full article ">Figure 4
Assembled sensor well, membrane, and filament. Full article ">Figure 5
Well activation with simulated ISF (45× Optical Magnification): (a) Top of dry well prior to filling; (b) Well above membrane filled with water before activation; (c) Well immediately after activation; (d) Well thirty seconds post-activation; (e) Well two minutes post-activation; (f) Well with sensing strip removed. Full article ">Figure 6
Explosive decomposition of well membrane (45× optical magnification) (a) before activation; (b) during activation; (c) after activation. Full article ">

26 pages, 3580 KiB

Open AccessReview

Current Advancements and Future Road Map to Develop ASSURED Microfluidic Biosensors for Infectious and Non-Infectious Diseases

by Tanu Bhardwaj, Lakshmi Narashimhan Ramana and Tarun Kumar Sharma

Biosensors 2022, 12(5), 357; https://doi.org/10.3390/bios12050357 - 20 May 2022

Cited by 21 | Viewed by 4899

Abstract

Better diagnostics are always essential for the treatment and prevention of a disease. Existing technologies for detecting infectious and non-infectious diseases are mostly tedious, expensive, and do not meet the World Health Organization’s (WHO) ASSURED (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, [...] Read more.

Better diagnostics are always essential for the treatment and prevention of a disease. Existing technologies for detecting infectious and non-infectious diseases are mostly tedious, expensive, and do not meet the World Health Organization’s (WHO) ASSURED (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, and deliverable to end user) criteria. Hence, more accurate, sensitive, and faster diagnostic technologies that meet the ASSURED criteria are highly required for timely and evidenced-based treatment. Presently, the diagnostics industry is finding interest in microfluidics-based biosensors, as this integration comprises all qualities, such as reduction in the size of the equipment, rapid turnaround time, possibility of parallel multiple analysis or multiplexing, etc. Microfluidics deal with the manipulation/analysis of fluid within micrometer-sized channels. Biosensors comprise biomolecules immobilized on a physicochemical transducer for the detection of a specific analyte. In this review article, we provide an outline of the history of microfluidics, current practices in the selection of materials in microfluidics, and how and where microfluidics-based biosensors have been used for the diagnosis of infectious and non-infectious diseases. Our inclination in this review article is toward the employment of microfluidics-based biosensors for the improvement of already existing/traditional methods in order to reduce efforts without compromising the accuracy of the diagnostic test. This article also suggests the possible improvements required in microfluidic chip-based biosensors in order to meet the ASSURED criteria. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Bansi D. Malhotra—From Nanosystems to a Biosensing Prototype for an Efficient Diagnostic)

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26 pages, 2323 KiB

Open AccessReview

Electronic Sensor Technologies in Monitoring Quality of Tea: A Review

by Seyed Mohammad Taghi Gharibzahedi, Francisco J. Barba, Jianjun Zhou, Min Wang and Zeynep Altintas

Biosensors 2022, 12(5), 356; https://doi.org/10.3390/bios12050356 - 20 May 2022

Cited by 32 | Viewed by 6392

Abstract

Tea, after water, is the most frequently consumed beverage in the world. The fermentation of tea leaves has a pivotal role in its quality and is usually monitored using the laboratory analytical instruments and olfactory perception of tea tasters. Developing electronic sensing platforms [...] Read more.

Tea, after water, is the most frequently consumed beverage in the world. The fermentation of tea leaves has a pivotal role in its quality and is usually monitored using the laboratory analytical instruments and olfactory perception of tea tasters. Developing electronic sensing platforms (ESPs), in terms of an electronic nose (e-nose), electronic tongue (e-tongue), and electronic eye (e-eye) equipped with progressive data processing algorithms, not only can accurately accelerate the consumer-based sensory quality assessment of tea, but also can define new standards for this bioactive product, to meet worldwide market demand. Using the complex data sets from electronic signals integrated with multivariate statistics can, thus, contribute to quality prediction and discrimination. The latest achievements and available solutions, to solve future problems and for easy and accurate real-time analysis of the sensory-chemical properties of tea and its products, are reviewed using bio-mimicking ESPs. These advanced sensing technologies, which measure the aroma, taste, and color profiles and input the data into mathematical classification algorithms, can discriminate different teas based on their price, geographical origins, harvest, fermentation, storage times, quality grades, and adulteration ratio. Although voltammetric and fluorescent sensor arrays are emerging for designing e-tongue systems, potentiometric electrodes are more often employed to monitor the taste profiles of tea. The use of a feature-level fusion strategy can significantly improve the efficiency and accuracy of prediction models, accompanied by the pattern recognition associations between the sensory properties and biochemical profiles of tea. Full article

(This article belongs to the Special Issue Biosensors in 2022)

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Images of different tea types (a) and chemical structures of theaflavins (b) and thearubigins (c) present in black tea. EC: epicatechin, EGC: epigallocatechin, ECG: epicatechin gallate, EGCG: epigallocatechin gallate. Full article ">Figure 2
(a) A lab-made e-nose with eight MOS gas sensors used in the production line of a tea factory, consisting of a computer with chemometric tools (A), the main part of e-nose device equipped to a sampling system having two electronic valves (three-way system) for the airflow control (B), and the sample chamber (C), and (b) a graphic diagram of the e-nose tool (DAQ is the data acquisition unit). Reprinted from Hidayat et al. [<a href="#B57-biosensors-12-00356" class="html-bibr">57</a>]. Full article ">Figure 3
A developed gas-sensing system for smell discrimination and fermentation monitoring in the on-line production of oolong tea. The image was retrieved from Tseng et al. [<a href="#B58-biosensors-12-00356" class="html-bibr">58</a>] with some modifications. Full article ">Figure 4
Images of three common potentiometric e-tongue systems for measuring the taste attributes of tea: (a) SA-402B (Intelligent Sensor Technology Co., Ltd., Japan; reprinted from Liu et al. [<a href="#B107-biosensors-12-00356" class="html-bibr">107</a>]) (a, for measuring the aftertaste value; b and c, for cleaning the sample rapidly; d and e: for cleaning the positive and negative solution; f: for the positive and negative cleaning solution; g: for the sensor calibration; h: for sensor reset; i: for the liquor sample), (b) TS-5000Z (Insent Inc., Atsugi-Shi, Japan), and (c) ASTREE (Alpha MOS Inc., Toulouse, France). Full article ">Figure 5
A diagram of a polyphenol evaluation model present in black, green, and yellow teas, based on feature fusion of an e-nose and hyperspectral imagery. FdF: frequency-domain feature, TdF: time-domain feature, Grid-SVR: grid support vector regression, RF: random forest, XGBoost: extreme gradient boosting. Retrieved from Yang et al. [<a href="#B77-biosensors-12-00356" class="html-bibr">77</a>]. Full article ">

16 pages, 2541 KiB

Open AccessArticle

An Artifact-Resistant Feature SKNAER for Quantifying the Burst of Skin Sympathetic Nerve Activity Signal

by Yantao Xing, Yike Zhang, Zhijun Xiao, Chenxi Yang, Jiayi Li, Chang Cui, Jing Wang, Hongwu Chen, Jianqing Li and Chengyu Liu

Biosensors 2022, 12(5), 355; https://doi.org/10.3390/bios12050355 - 20 May 2022

Cited by 9 | Viewed by 2758

Abstract

Evaluation of sympathetic nerve activity (SNA) using skin sympathetic nerve activity (SKNA) signal has attracted interest in recent studies. However, signal noises may obstruct the accurate location for the burst of SKNA, leading to the quantification error of the signal. In this study, [...] Read more.

Evaluation of sympathetic nerve activity (SNA) using skin sympathetic nerve activity (SKNA) signal has attracted interest in recent studies. However, signal noises may obstruct the accurate location for the burst of SKNA, leading to the quantification error of the signal. In this study, we use the Teager–Kaiser energy (TKE) operator to preprocess the SKNA signal, and then candidates of burst areas were segmented by an envelope-based method. Since the burst of SKNA can also be discriminated by the high-frequency component in QRS complexes of electrocardiogram (ECG), a strategy was designed to reject their influence. Finally, a feature of the SKNA energy ratio (SKNAER) was proposed for quantifying the SKNA. The method was verified by both sympathetic nerve stimulation and hemodialysis experiments compared with traditional heart rate variability (HRV) and a recently developed integral skin sympathetic nerve activity (iSKNA) method. The results showed that SKNAER correlated well with HRV features (r = 0.60 with the standard deviation of NN intervals, 0.67 with low frequency/high frequency, 0.47 with very low frequency) and the average of iSKNA (r = 0.67). SKNAER improved the detection accuracy for the burst of SKNA, with 98.2% for detection rate and 91.9% for precision, inducing increases of 3.7% and 29.1% compared with iSKNA (detection rate: 94.5% (p < 0.01), precision: 62.8% (p < 0.001)). The results from the hemodialysis experiment showed that SKNAER had more significant differences than aSKNA in the long-term SNA evaluation (p < 0.001 vs. p = 0.07 in the fourth period, p < 0.01 vs. p = 0.11 in the sixth period). The newly developed feature may play an important role in continuously monitoring SNA and keeping potential for further clinical tests. Full article

(This article belongs to the Special Issue Intelligent Biosignal Processing in Wearable and Implantable Sensors)

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(a) The chain of SKNA signal transmission and acquisition. (b) Representative examples of acquired signals: the above figure shows the raw signal and the following figure shows SKNA after filtering. (c) The step signal artifact. (d) The ECG artifact. Full article ">Figure 2
The electrode placement position in the experiment. In Experiment 2, the signal is only collected from channel 1. Full article ">Figure 3
Representative examples of signal preprocessing and segmentation processes using the QRS information complexes and a sensitive threshold. (a) The raw signal. (b) The filtered SKNA signal. (c) The preprocessed signal after TKE operator. (d) The segmented burst area based on envelope and integral signal. (e) The final segmented burst area. The burst was in the blue box, the baseline was in the yellow box, and the artifact was in the red box. Full article ">Figure 4
(a–d) The correlation between SKNAER and HRV features of the ten patients before and after sympathetic activation in Experiment 1. Full article ">Figure 5
(a–e) The statistical results of the features related to the sympathetic nervous activity before and after sympathetic activation in Experiment 1. * p < 0.05, *** p < 0.001. Full article ">Figure 6
(a–e) The trend of the SKNA and HRV features in the twenty patients during four-hour hemodialysis. * p < 0.05, ** p < 0.01, *** p < 0.001. Full article ">

10 pages, 1440 KiB

Open AccessArticle

Acetone Gas Sensor Based on SWCNT/Polypyrrole/Phenyllactic Acid Nanocomposite with High Sensitivity and Humidity Stability

by Jun-Ho Byeon, Ji-Sun Kim, Hyo-Kyung Kang, Sungmin Kang and Jin-Yeol Kim

Biosensors 2022, 12(5), 354; https://doi.org/10.3390/bios12050354 - 19 May 2022

Cited by 11 | Viewed by 2728

Abstract

We synthesized core-shell-shaped nanocomposites composed of a single-walled carbon nanotube (SWCNT) and heptadecafluorooctanesulfonic acid-doped polypyrrole (C8F-doped-PPy)/phenyllatic acid (PLA), i.e., C8F-doped-PPy/PLA@SWCNT, for detecting acetone gas with high sensitivity and humidity stability. The obtained nanocomposites have the structural features of a sensing material as a [...] Read more.

We synthesized core-shell-shaped nanocomposites composed of a single-walled carbon nanotube (SWCNT) and heptadecafluorooctanesulfonic acid-doped polypyrrole (C8F-doped-PPy)/phenyllatic acid (PLA), i.e., C8F-doped-PPy/PLA@SWCNT, for detecting acetone gas with high sensitivity and humidity stability. The obtained nanocomposites have the structural features of a sensing material as a C8F-doped-PPy layer surrounding a single-stranded SWCNT, and a PLA layer on the outer surface of the PPy as a specific sensing layer for acetone. PLA was chemically combined with the positively charged PPy backbone and provided the ability to reliably detect acetone gas at concentrations as low as 50 ppb even at 25 °C, which is required for medical diagnoses via human breath analysis. When C8F was contained in the pyrrole monomer in a ratio of 0.1 mol, it was able to stably detect an effective signal in a relative humidity (RH) of 0–80% range. Full article

(This article belongs to the Special Issue Application of Nanomaterials for Biosensors)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
Schematic of and the chemical structure of C8F-doped-PPy/PLA@SWCNT core-shell-shaped nanocomposites for C3H6O gas sensing. Full article ">Figure 2
(I) The scanning electron microscopy (SEM) and (II) transmission core–shell-shaped nanorods (sample). (III) The surface plasmon absorption spectrum of the samples and (IV) the electrical resistance (Ω) of the sensor sample of the as-cast film formed as a function of the relative thickness (thickness converted concerning the light transmittance (%) at a 550 nm wavelength of the casting film). Full article ">Figure 3
(I) The Fourier transform infrared (FT-IR) spectra of the C8F-doped-PPy/PLA@ SWCNT nanocomposite: (a) the C8F-doped-PPy/PLA@ SWCNT composite, (b) the C8F-doped PPy@SWCNT nanorods, and (c) the PLA. In the figure, the meaning of ‘*’ indicates the IR absorp-tion peak of PLA molecules. The presence or absence of PLA present in the surface layer of C8F-doped-PPy/PLA@ SWCNT nanocomposite is expressed. (II) The FT-Raman spectra of the C8F-doped-PPy/PLA@ SWCNT nanocomposite: (a) the C8F-doped-PPy/PLA@ SWCNT composite, (b) the C8F-doped-PPy nanorods, and (c) the SWCNT. (The dotted line indicates that the Raman intensity changed as the stretching mode of C8F-doped-PPy and the tangential mode of SWCNT overlapped). Full article ">Figure 4
(I) The continuous dynamic response of the C8F-doped-PPy/PLA@SWCNT sensor to different concentrations of C3H6O (1–5 ppm) at 25 °C and in 0% RH (dry air). (a) The C8F-doped-PPy@ SWCNT (PLA-free). (b–d) The PLA groups were linked in a 0.1, 0.3, and 0.5 mol ratio to the positively charged PPy backbone on a C8F-doped-PPy/PLA@SWCNT nanocomposite, respectively. (II) The response characteristics of the C8F-doped-PPy/PLA0.5@SWCNT sensor with C3H6O in the 50–100 ppb concentration range at 25 °C and in 0% RH (dry air): (a) 100 ppb and (b) 50 ppb. Full article ">Figure 5
The sensitivity of the (a) C8F-doped-PPy/PLA0.5@SWCNT sensor and (b) C8F-doped-PPy/PLA0.0@SWCNT sensor observed by exposure to 50–5000 ppb of C3H6O gas. Full article ">Figure 6
(I) The continuous dynamic response of the C8F0.1-doped-PPy/PLA0.5@SWCNT sensor to different humidity conditions with C3H6O gas at 5 ppm at 25 °C. (II) Sensitivity change with increasing humidity measured at each gas concentration: (a) 5 ppm, (b) 2.5 ppm, and (c) 1 ppm. Full article ">

8 pages, 1314 KiB

Open AccessArticle

Bioluminescent-Inhibition-Based Biosensor for Full-Profile Soil Contamination Assessment

by Elizaveta M. Kolosova, Oleg S. Sutormin, Aleksandr A. Shpedt, Ludmila V. Stepanova and Valentina A. Kratasyuk

Biosensors 2022, 12(5), 353; https://doi.org/10.3390/bios12050353 - 19 May 2022

Cited by 4 | Viewed by 2477

Abstract

A bioluminescent-enzyme-inhibition-based assay was applied to predict the potential toxicity of the full profile of the following soil samples: agricultural grassland, 10-year fallow land (treated with remediation processes for 10 years) and uncontaminated (virgin) land. This assay specifically detects the influence of aqueous [...] Read more.

A bioluminescent-enzyme-inhibition-based assay was applied to predict the potential toxicity of the full profile of the following soil samples: agricultural grassland, 10-year fallow land (treated with remediation processes for 10 years) and uncontaminated (virgin) land. This assay specifically detects the influence of aqueous soil extracts from soils on the activity of a coupled enzyme system of luminescent bacteria: NAD(P)H:FMN-oxidoreductase + luciferase (Red + Luc). It was shown that the inhibitory effect of the full-profile soil samples on the Red + Luc system decreased with depth for the 10-year fallow-land and virgin-land samples, which correlated with a decrease in the humic organic matter content in the soils. The inhibitory effect of the agricultural grassland on the Red + Luc enzyme system activity was more complex and involved the presence of the humic organic matter content, as well as the presence of pollutants in the whole-soil profile. However, if the interfering effect of humic organic substances on the Red + Luc system’s activity is taken into account during full-profile soil toxicity assessments, it might help to detect pollutant mobility and its leaching into the subsoil layer. Thus, this bioluminescent method, due to the technical simplicity, rapid response time and high sensitivity, has the potential to be developed as a biological part of the inhibition-based assay and/or biosensors for the preventive tracing of potential full-profile soil contamination. Full article

(This article belongs to the Special Issue Developments and Applications of Bioluminescent and Chemiluminescent Sensors and Probes)

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16 pages, 6619 KiB

Open AccessArticle

Fiber-Optic Distributed Sensing Network for Thermal Mapping of Gold Nanoparticles-Mediated Radiofrequency Ablation

by Akbota Sametova, Sabit Kurmashev, Zhannat Ashikbayeva, Aida Amantayeva, Wilfried Blanc, Timur Sh. Atabaev and Daniele Tosi

Biosensors 2022, 12(5), 352; https://doi.org/10.3390/bios12050352 - 18 May 2022

Cited by 7 | Viewed by 2628

Abstract

In this work, we report the design of an optical fiber distributed sensing network for the 2-dimensional (2D) in situ thermal mapping of advanced methods for radiofrequency thermal ablation. The sensing system is based on six high-scattering MgO-doped optical fibers, interleaved by a [...] Read more.

In this work, we report the design of an optical fiber distributed sensing network for the 2-dimensional (2D) in situ thermal mapping of advanced methods for radiofrequency thermal ablation. The sensing system is based on six high-scattering MgO-doped optical fibers, interleaved by a scattering-level spatial multiplexing approach that allows simultaneous detection of each fiber location, in a 40 × 20 mm grid (7.8 mm² pixel size). Radiofrequency ablation (RFA) was performed on bovine phantom, using a pristine approach and methods mediated by agarose and gold nanoparticles in order to enhance the ablation properties. The 2D sensors allow the detection of spatiotemporal patterns, evaluating the heating properties and investigating the repeatability. We observe that agarose-based ablation yields the widest ablated area in the best-case scenario, while gold nanoparticles-mediated ablation provides the best trade-off between the ablated area (53.0–65.1 mm², 61.5 mm² mean value) and repeatability. Full article

(This article belongs to the Special Issue Photonics for Bioapplications: Sensors and Technology)

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12 pages, 1540 KiB

Open AccessArticle

Investigation and Comparison of Specific Antibodies’ Affinity Interaction with SARS-CoV-2 Wild-Type, B.1.1.7, and B.1.351 Spike Protein by Total Internal Reflection Ellipsometry

by Ieva Plikusiene, Vincentas Maciulis, Silvija Juciute, Ruta Maciuleviciene, Saulius Balevicius, Arunas Ramanavicius and Almira Ramanaviciene

Biosensors 2022, 12(5), 351; https://doi.org/10.3390/bios12050351 - 18 May 2022

Cited by 15 | Viewed by 3390

Abstract

SARS-CoV-2 vaccines provide strong protection against COVID-19. However, the emergence of SARS-CoV-2 variants has raised concerns about the efficacy of vaccines. In this study, we investigated the interactions of specific polyclonal human antibodies (pAb-SCoV2-S) produced after vaccination with the Vaxzevria vaccine with the [...] Read more.

SARS-CoV-2 vaccines provide strong protection against COVID-19. However, the emergence of SARS-CoV-2 variants has raised concerns about the efficacy of vaccines. In this study, we investigated the interactions of specific polyclonal human antibodies (pAb-SCoV2-S) produced after vaccination with the Vaxzevria vaccine with the spike proteins of three SARS-CoV-2 variants of concern: wild-type, B.1.1.7, and B.1.351. Highly sensitive, label-free, and real-time monitoring of these interactions was accomplished using the total internal reflection ellipsometry method. Thermodynamic parameters such as association and dissociation rate constants, the stable immune complex formation rate constant (k_r), the equilibrium association and dissociation (K_D) constants and steric factors (P_s) were calculated using a two-step irreversible binding mathematical model. The results obtained show that the K_D values for the specific antibody interactions with all three types of spike protein are in the same nanomolar range. The K_D values for B.1.1.7 and B.1.351 suggest that the antibody produced after vaccination can successfully protect the population from the alpha (B.1.1.7) and beta (B.1.351) SARS-CoV-2 mutations. The steric factors (P_s) obtained for all three types of spike proteins showed a 100-fold lower requirement for the formation of an immune complex when compared with nucleocapsid protein. Full article

(This article belongs to the Special Issue Optical, Electrochemical and Acoustic Methods Based Biosensors for the Investigation of Biomolecules Interactions)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
(A) Schematic representation of SARS-CoV-2 S protein (SCoV2-S, SCoV2-αS, or SCoV2-βS) covalent immobilization on the gold-coated SPR sensor disc pre-modified with 11-MUA SAM. (B) The principle scheme representing total internal reflection ellipsometry measurements. (C) Schematic representation of SCoV2-S, SCoV2-αS, and SCoV2-βS covalent immobilization and interaction with specific polyclonal antibodies (pAb-SCoV2-S). Full article ">Figure 2
Time-resolved TIRE kinetics and ellipsometric parameters of SCoV2-S immobilization and interaction with specific polyclonal antibodies. (A) Kinetics of covalent SCoV2-S immobilization on 11-MUA SAM modified gold-coated SPR sensor disc; (B) kinetics of polyclonal antibody interaction with covalently immobilized ScoV2-S at different serum dilutions (1:4, 1:10, 1:20, 1:30, and 1:40); (C) Δ and (D) Ψ spectral shift after immune complex formation using the same dilutions of polyclonal antibodies. Full article ">Figure 3
Time-resolved TIRE kinetics and ellipsometric parameters of SCoV2-αS immobilization and interaction with specific polyclonal antibodies. (A) Kinetics of covalent SCoV2α-S immobilization on 11-MUA SAM modified gold-coated SPR sensor disc; (B) kinetics of polyclonal antibody interaction with covalently immobilized SCoV2-αS at 1:40 dilution of serum; (C) Δ and (D) Ψ spectral shift after immune complex formation using the same dilutions of polyclonal antibodies. Full article ">Figure 4
Time-resolved TIRE kinetics and ellipsometric parameters of SCoV2-βS immobilization and interaction with specific polyclonal antibodies. (A) Kinetics of covalent SCoV2β-S immobilization on 11-MUA SAM modified gold-coated SPR sensor disc; (B) kinetics of polyclonal antibody interaction with covalently immobilized SCoV2-βS at 1:40 dilution of serum; (C) Δ and (D) Ψ spectral shift after the formation of immune complexes using the same dilutions of polyclonal antibodies. Full article ">Figure 5
Normalized pAb-SCoV2-S antibody surface concentration (f) evolution in time obtained using 1:40 diluted blood serum during the formation of the immune complex with (A) SCoV2-S, (B) SCoV2-αS, (C) SCoV2-βS. Points correspond to experimentally obtained results, while lines for fitting are derived by using two-step irreversible binding immune complex formation mathematical modeling. Full article ">

10 pages, 2087 KiB

Open AccessArticle

Easy-to-Operate Co-Flow Step Emulsification Device for High-Throughput Three-Dimensional Cell Culture

by Chunyang Wei, Chengzhuang Yu, Shanshan Li, Tiejun Li, Jiyu Meng and Junwei Li

Biosensors 2022, 12(5), 350; https://doi.org/10.3390/bios12050350 - 18 May 2022

Viewed by 2750

Abstract

Cell culture plays an essential role in tissue engineering and high-throughput drug screening. Compared with two-dimensional (2D) in vitro culture, three-dimensional (3D) in vitro culture can mimic cells in vivo more accurately, including complex cellular organizations, heterogeneity, and cell–extracellular matrix (ECM) interactions. This [...] Read more.

Cell culture plays an essential role in tissue engineering and high-throughput drug screening. Compared with two-dimensional (2D) in vitro culture, three-dimensional (3D) in vitro culture can mimic cells in vivo more accurately, including complex cellular organizations, heterogeneity, and cell–extracellular matrix (ECM) interactions. This article presents a droplet-based microfluidic chip that integrates cell distribution, 3D in vitro cell culture, and in situ cell monitoring in a single device. Using the microfluidic “co-flow step emulsification” approach, we have successfully prepared close-packed droplet arrays with an ultra-high-volume fraction (72%) which can prevent cells from adhering to the chip surface so as to achieve a 3D cell culture and make scalable and high-throughput cell culture possible. The proposed device could produce droplets from 55.29 ± 1.52 to 95.64 ± 3.35 μm, enabling the diverse encapsulation of cells of different sizes and quantities. Furthermore, the cost for each microfluidic CFSE chip is approximately USD 3, making it a low-cost approach for 3D cell culture. The proposed device is successfully applied in the 3D culture of saccharomyces cerevisiae cells with an occurrence rate for proliferation of 80.34 ± 3.77%. With low-cost, easy-to-operate, high-throughput, and miniaturization characteristics, the proposed device meets the requirements for 3D in vitro cell culture and is expected to be applied in biological fields such as drug toxicology and pharmacokinetics. Full article

(This article belongs to the Collection Microsystems for Cell Cultures)

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Typical microfluidic 3D cell culture methods: (a,b) hanging drop; (c) T-junction; (d) flow-focusing; (e) coxial flow; (f) co-flow step emulsification (CFSE). Full article ">Figure 2
Punching fabrication. (a) I: Schematic diagram of the punching operation (b) Three typical illustrations of the step microstructures. I: The cylindrical hole is below the central line of the straight microchannel. II: The cylindrical hole is right on the central line of the straight microchannel. III: The cylindrical hole is above the central line of the straight microchannel. (c) Microscopic images of the step boundaries, corresponding to the illustrations above. It is worth noting that the bio-puncher can smoothly cut the straight channels without edge-tearing or cracking. Full article ">Figure 3
CFSE-based droplet generation. (a) Schematic of the 3D cell culture system. I: The system consists of a micropump, pressure controller, fluid tubes, CFSE chip, and inverted microscope; II: Schematic diagram of the “co-flow step emulsification”. (b) Optical photograph of the microfluidic CFSE device. I: Cell medium and oil were pumped into the microchannels; II: The cell medium broke into emulsion droplets. (c) Cell clusters in medium (I) and in droplets (II). (d) The resulting droplets bulk the cylindrical reservoir within several minutes with an ultra-high-volume fraction (φ = 72%, Qinner-phase = 1.28 μL/min, Qouter-phase = 0.49 μL/min, Φ = 80.38 ± 2.18 μm). I–VI shows the droplet perfusion process in the cylindrical storage reservoir in 30 seconds. (e) The close-packed droplet arrays arrange themselves in a hexagonal pattern. I–VI demonstrate the droplet arrays of six layers arranged from top to bottom. VII demonstrates the stacked status of the droplet arrays. Full article ">Figure 4
Investigation of the CFSE-based 3D cell culture system. (a) Time-dependence of droplet numbers. (b) Plot of emulsion droplet diameter as a function of running time, to show the time-stability of the microfluidic CFSE device. The cell medium and oil flow rates were set at 1.28 μL/min and 0.49 μL/min. (c) Measured diameters of the droplets were plotted against the different cell medium flowrate conditions. The inset microscopic images show the droplets with diameters of 62.62 ± 1.95 μm and 91.09 ± 2.26 μm, respectively. (d) The relationship between cell number per droplet and cell density in the medium. (e) Illustration and microscopic images of the proliferation process of saccharomyces cerevisiae cell. I: A saccharomyces cerevisiae cell was encapsulated in a droplet; II: The saccharomyces cerevisiae cell began to bud and proliferate; III: The saccharomyces cerevisiae cell kept proliferating for 200 min. Scale bar: 30 μm. Full article ">

8 pages, 1773 KiB

Open AccessBrief Report

How Paretic and Non-Paretic Ankle Muscles Contract during Walking in Stroke Survivors: New Insight Using Novel Wearable Ultrasound Imaging and Sensing Technology

by Pei-Zhao Lyu, Ringo Tang-Long Zhu, Yan To Ling, Li-Ke Wang, Yong-Ping Zheng and Christina Zong-Hao Ma

Biosensors 2022, 12(5), 349; https://doi.org/10.3390/bios12050349 - 18 May 2022

Cited by 10 | Viewed by 2973

Abstract

Abnormal muscle tone and muscle weakness are related to gait asymmetry in stroke survivors. However, the internal muscle morphological changes that occur during walking remain unclear. To address this issue, this study investigated the muscle activity of the tibialis anterior (TA) and medial [...] Read more.

Abnormal muscle tone and muscle weakness are related to gait asymmetry in stroke survivors. However, the internal muscle morphological changes that occur during walking remain unclear. To address this issue, this study investigated the muscle activity of the tibialis anterior (TA) and medial gastrocnemius (MG) of both the paretic and non-paretic sides during walking in nine stroke survivors, by simultaneously capturing electromyography (EMG), mechanomyography (MMG), and ultrasound images, and using a validated novel wearable ultrasound imaging and sensing system. Statistical analysis was performed to examine the test–retest reliability of the collected data, and both the main and interaction effects of each “side” (paretic vs. non-paretic) and “gait” factors, in stroke survivors. This study observed significantly good test–retest reliability in the collected data (0.794 ≤ ICC ≤ 0.985), and significant differences existed in both the side and gait factors of the average TA muscle thickness from ultrasound images, and in the gait factors of TA and MG muscle’s MMG and EMG signals (p < 0.05). The muscle morphological characteristics also appeared to be different between the paretic and non-paretic sides on ultrasound images. This study uncovered significantly different internal muscle contraction patterns between paretic and non-paretic sides during walking for TA (7.2% ± 1.6%) and MG (5.3% ± 4.9%) muscles in stroke survivors. Full article

(This article belongs to the Section Biosensors and Healthcare)

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24 pages, 16174 KiB

Open AccessReview

AIE-Active Photosensitizers: Manipulation of Reactive Oxygen Species Generation and Applications in Photodynamic Therapy

by Hao Yu, Binjie Chen, Huiming Huang, Zhentao He, Jiangman Sun, Guan Wang, Xinggui Gu and Ben Zhong Tang

Biosensors 2022, 12(5), 348; https://doi.org/10.3390/bios12050348 - 18 May 2022

Cited by 37 | Viewed by 6279

Abstract

Photodynamic therapy (PDT) is a non-invasive approach for tumor elimination that is attracting more and more attention due to the advantages of minimal side effects and high precision. In typical PDT, reactive oxygen species (ROS) generated from photosensitizers play the pivotal role, determining [...] Read more.

Photodynamic therapy (PDT) is a non-invasive approach for tumor elimination that is attracting more and more attention due to the advantages of minimal side effects and high precision. In typical PDT, reactive oxygen species (ROS) generated from photosensitizers play the pivotal role, determining the efficiency of PDT. However, applications of traditional PDT were usually limited by the aggregation-caused quenching (ACQ) effect of the photosensitizers employed. Fortunately, photosensitizers with aggregation-induced emission (AIE-active photosensitizers) have been developed with biocompatibility, effective ROS generation, and superior absorption, bringing about great interest for applications in oncotherapy. In this review, we review the development of AIE-active photosensitizers and describe molecule and aggregation strategies for manipulating photosensitization. For the molecule strategy, we describe the approaches utilized for tuning ROS generation by attaching heavy atoms, constructing a donor-acceptor effect, introducing ionization, and modifying with activatable moieties. The aggregation strategy to boost ROS generation is reviewed for the first time, including consideration of the aggregation of photosensitizers, polymerization, and aggregation microenvironment manipulation. Moreover, based on AIE-active photosensitizers, the cutting-edge applications of PDT with NIR irradiated therapy, activatable therapy, hypoxic therapy, and synergistic treatment are also outlined. Full article

(This article belongs to the Special Issue Development of Aggregation-Induced Emission Materials and Their Applications in Biosensing, Bioimaging and Theranostics)

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13 pages, 2428 KiB

Open AccessArticle

An Aptamer-Functionalised Schottky-Field Effect Transistor for the Detection of Proteins

by Thomas Farrow, Siriny Laumier, Ian Sandall and Harm van Zalinge

Biosensors 2022, 12(5), 347; https://doi.org/10.3390/bios12050347 - 18 May 2022

Cited by 10 | Viewed by 3180

Abstract

The outbreak of the coronavirus disease 2019 (COVID-19) in December 2019 has highlighted the need for a flexible sensing system that can quickly and accurately determine the presence of biomarkers associated with the disease. This sensing system also needs to be easily adaptable [...] Read more.

The outbreak of the coronavirus disease 2019 (COVID-19) in December 2019 has highlighted the need for a flexible sensing system that can quickly and accurately determine the presence of biomarkers associated with the disease. This sensing system also needs to be easily adaptable to incorporate both novel diseases as well as changes in the existing ones. Here we report the feasibility of using a simple, low-cost silicon field-effect transistor functionalised with aptamers and designed to attach to the spike protein of SARS-CoV2. It is shown that a linear response can be obtained in a concentration range of 100 fM to 10 pM. Furthermore, by using a larger range of source-drain potentials compared with other FET based sensors, it is possible to look at a wider range of device parameters to optimise the response. Full article

(This article belongs to the Special Issue Feature Issue of Biosensors and Bioelectronic Devices Section)

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Schematic of the functionalisation process and subsequent detection of the spike protein. An aluminium contact is deposited on an intrinsic silicon sample. The device is functionalised with APTES, glutaraldehyde (GA), aptamer and glycine molecules in this order. The glycine is aimed at terminating any unbound aldehydes, which might create non-specific binding sites. In the final step, the process of detection is visualised inside the electrode gap. For clarity the aptamers and protein are only shown in the area between the electrodes; however, they are present everywhere on the silicon. At the bottom right is a photograph of the actual devices. Full article ">Figure 2
The IV-characteristics of the bare silicon device between the source and drain contact. The inset shows the log-log plot of the positive bias potentials. The red dotted lines indicate the slope, which is 1, indicating Ohmic behaviour at low potential and 0.5 at higher voltage. Full article ">Figure 3
A schematic representation of the experiment. (a) shows the band diagram at the interface between the SiO2 and the Si; the formation of the channel due to the band-bending is indicated. In (b) the effect of the presence of the aptamers and protein is indicated. At the top, the general layout of the FET is shown. The steps below illustrate the major points in the experiment. The ‘empty’ circles represent equal amounts of electrons and holes, whereas an area with a pre-dominantly negative or positive charge is indicated with a minus or plus signs, respectively. Full article ">Figure 4
IV-characteristics of a functionalised device with a spike protein concentration of 1 pM. The arrows and numbers indicate the direction of the voltage sweep. During the upsweep (1) a FET type characteristic is observed, and the return sweep (2) show hysteresis caused by slow moving ions. Full article ">Figure 5
(a) IV-characteristics of a functionalised device with at varying spike protein concentrations (up sweep only). (b) The relative change of the current as a function of bias potential. Full article ">Figure 6
(a) comparison between the current at +3 V (black) and the relative change (red). (b) comparison between the current (black) and the hysteresis (blue). Full article ">Figure 7
The output resistance as a function of the spike protein concentration. The red line indicates the trend line. The inset shows the lambda parameter which is related to the channel shortening. The arrow at 100 fM indicates an omitted point at λ = 33.4 V−1. Full article ">Figure 8
(a) comparison between the current at +3 V for BSA (black) and spike protein (red). (b) comparison between the current for spike protein in artificial saliva (black) and PBS (red). Full article ">

18 pages, 5287 KiB

Open AccessArticle

Kinetics of Isothermal Dumbbell Exponential Amplification: Effects of Mix Composition on LAMP and Its Derivatives

by Maud Savonnet, Mathilde Aubret, Patricia Laurent, Yoann Roupioz, Myriam Cubizolles and Arnaud Buhot

Biosensors 2022, 12(5), 346; https://doi.org/10.3390/bios12050346 - 18 May 2022

Cited by 8 | Viewed by 3453

Abstract

Loop-mediated isothermal amplification (LAMP) is an exponential amplification method of DNA strands that is more and more used for its high performances. Thanks to its high sensitivity and selectivity, LAMP found numerous applications from the detection of pathogens or viruses through their genome [...] Read more.

Loop-mediated isothermal amplification (LAMP) is an exponential amplification method of DNA strands that is more and more used for its high performances. Thanks to its high sensitivity and selectivity, LAMP found numerous applications from the detection of pathogens or viruses through their genome amplification to its incorporation as an amplification strategy in protein or miRNA biomarker quantification. The LAMP method is composed of two stages: the first one consists in the transformation of the DNA strands into dumbbell structures formed of two stems and loops thanks to four primers; then, in the second stage, only two primers are required to amplify the dumbbells exponentially in numerous hairpins of increasing lengths. In this paper, we propose a theoretical framework to analyze the kinetics of the second stage of LAMP, the isothermal dumbbell exponential amplification (IDEA) as function of the physico-chemical parameters of the amplification reaction. Dedicated experiments validate the models. We believe these results may help the optimization of LAMP performances by reducing the number of experiments necessary to find the best parameters. Full article

(This article belongs to the Special Issue Advances in Amplification Methods for Biosensors)

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14 pages, 3547 KiB

Open AccessArticle

Analyzing Human Periodontal Soft Tissue Inflammation and Drug Responses In Vitro Using Epithelium-Capillary Interface On-a-Chip

by Laidi Jin, Ni Kou, Fan An, Zehang Gao, Tian Tian, Jianan Hui, Chen Chen, Guowu Ma, Hongju Mao and Huiying Liu

Biosensors 2022, 12(5), 345; https://doi.org/10.3390/bios12050345 - 18 May 2022

Cited by 15 | Viewed by 3438

Abstract

The gingival epithelium–capillary interface is a unique feature of periodontal soft tissue, preserving periodontal tissue homeostasis and preventing microorganism and toxic substances from entering the subepithelial tissue. However, the function of the interface is disturbed in periodontitis, and mechanisms of the breakdown of [...] Read more.

The gingival epithelium–capillary interface is a unique feature of periodontal soft tissue, preserving periodontal tissue homeostasis and preventing microorganism and toxic substances from entering the subepithelial tissue. However, the function of the interface is disturbed in periodontitis, and mechanisms of the breakdown of the interface are incompletely understood. To address these limitations, we developed a microfluidic epithelium–capillary barrier with a thin culture membrane (10 μm) that closely mimics the in vivo gingival epithelial barrier with an immune micro-environment. To test the validity of the fabricated gingival epithelial barrier model, epithelium–capillary interface-on-a-chip was cultured with human gingival epithelial cells (HGECs) and human vascular endothelial cells (HUVEC). Their key properties were tested using optical microscope, transepithelial/transendothelial electrical resistance (TEER), and permeability assays. The clear expression of VE-cadherin revealed the tight junctions in endothelial cells. Live/dead assays indicated a high cell viability, and the astrocytic morphology of HGE cells was confirmed by F-actin immunostaining. By the third day of cell culture, TEER levels typically exceeded in co-cultures. The resultant permeability coefficients showed a significant difference between 70 kDa and 40 kDa FITC-dextran. The expression of protein intercellular cell adhesion molecule (ICAM-1) and human beta defensin-2 (HBD2) decreased when exposed to TNF-α and LPS, but recovered with the NF-κB inhibitor treatment- Pyrrolidinedithiocarbamic acid (PDTC), indicating the stability of the fabricated chip. These results demonstrate that the developed epithelium-capillary interface system is a valid model for studying periodontal soft tissue function and drug delivery. Full article

(This article belongs to the Special Issue Microfluidic Based Organ-on-Chips and Biomedical Application)

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Schematic description of transepithelial/transendothelial electrical resistance assays. (a) HGECs are seeded onto the upper non-coated porous membrane of the transwell; (b) HUVEC are seeded onto the bottom non-coated porous membrane of the transwell; (c) HGECs and HUVEC are respectively cultured on the upper and bottom sides of the porous membrane within the transwell. Full article ">Figure 2
Primary gingival epithelial cells extraction and indirect immunocytochemical staining of cells with cytokeratin staining. (a) Human gingival tissue mass and the first passage HGECs showing slabstone-shaped; (b) HGECs immunohistochemical analysis with keratin antibody showing a positive result (the cytoplasm is brownish yellow, nuclear staining is negative, and it is blue after counterstaining with hematoxylin); (c) HUVEC as the control group, the expression of cytokeratin is negative. Full article ">Figure 3
TEER-measurements in HGECs, HUVEC cells, and co-culture of HGECs and HUVEC cells. Results are mean ± SD from three or more experiments and data are analyzed by two tailed student’s t-test *** p < 0.001 compared with the monolayer. Full article ">Figure 4
Structure and design of the developed epithelium–capillary interface-on-a-chip. (a) Victory anatomy of periodontal tissue; (b) the fully fabricated periodontal soft tissue chip, the system comprises two perpendicular flow channels: channel heights are 200 μm, and chambers radium are 4 mm (lumen and albumen); (c) the chip consists of two PDMS layers, and a piece of polycarbonate membrane; (d) close-up view. Channels model the lumenal (green) and ablumenal (blue) sides of the epithelium unit. HGEC and HUVEC cells are cultured on the lumenal and ablumenal sides of the enclosed porous membrane, respectively. Full article ">Figure 5
On-chip formation of an epithelium-capillary interface. (a,b) Live/dead stain (green: live, red: dead) of HUVEC and HGEC cells on day 3 of culture on the porous membranes. (c) Statistical analysis of cell viability. (d) Three-dimensional schematic diagram and (e,f) reconstructed views of interface formed by HUVEC and HGECs cells on the top PETE membrane tracked by celltrackerTM orange (HGECs) and celltrackerTM green (HUVEC). Full article ">Figure 6
Biological characterization of the two types of epithelium−capillary interface cells on chip. (a) Representative images of the expression of tight junction protein VE-cadherin (green) and DAPI (blue) of HUVEC; (b) the cytoskeleton of HGECs on membrane (red; stained with F−actin) are visualized with nucleus (blue; stained with DAPI); (c) the emission spectra and fluorescence intensity (emission at 518 nm) of different concentration standards of the 40 kDa FITC−dextran; (d) the emission spectra and fluorescence intensity (emission at 518 nm) of different concentration standards of the 70 kDa FITC−dextran; (e) the fluorescence image of the HUVEC cells layer (stained with celltrackerTM orange) on the porous membrane; (f) the apparent permeability (Papp) of soluble reagents with 40 kDa and 70 kDa molecular weight FITC−dextran through the HUVEC cells layer, n = 3. Error bars represent the standard error of the mean (SEM) of three independent experiments. Two-tailed significance was set to ** p < 0.01. Full article ">Figure 7
Periodontal soft tissue inflammation and therapeutic responses on-chip. (a) Schematic diagram of inflammation model and drug model; (b,c) the graphs show effects on production of the human CD54 (ICAM-1), Human DEFB2 (HBD2) stimulation with TNF-α (10 ng mL−1) in the absence or presence of medicine on the epithelium-capillary interface chip; (d,e) The graphs show effects on production of the ICAM-1, HBD2 stimulation with LPS (10 μg mL−1) in the absence or presence of PDTC on the epithelium–capillary interface chip. n = 3. Error bars represent the standard error of the mean (SEM) of three independent experiments. Two-tailed significance was set to * p < 0.05 and ** p < 0.01, *** p < 0.001. Full article ">

17 pages, 953 KiB

Open AccessReview

Diagnoses Based on C-Reactive Protein Point-of-Care Tests

by Miroslav Pohanka

Biosensors 2022, 12(5), 344; https://doi.org/10.3390/bios12050344 - 17 May 2022

Cited by 12 | Viewed by 10955

Abstract

C-reactive protein (CRP) is an important part of the immune system’s reaction to various pathological impulses such as bacterial infections, systemic inflammation, and internal organ failures. An increased CRP level serves to diagnose the mentioned pathological states. Both standard laboratory methods and simple [...] Read more.

C-reactive protein (CRP) is an important part of the immune system’s reaction to various pathological impulses such as bacterial infections, systemic inflammation, and internal organ failures. An increased CRP level serves to diagnose the mentioned pathological states. Both standard laboratory methods and simple point-of-care devices such as lateral flow tests and immunoturbidimetric assays serve for the instrumental diagnoses based on CRP. The current method for CRP has many flaws and limitations in its use. Biosensor and bioassay analytical devices are presently researched by many teams to provide more sensitive and better-suited tools for point-of-care tests of CRP in biological samples when compared to the standard methods. This review article is focused on mapping the diagnostical relevance of CRP, the applicability of the current analytical methods, and the recent innovations in the measurement of CRP level. Full article

(This article belongs to the Section Biosensor and Bioelectronic Devices)

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10 pages, 2820 KiB

Open AccessArticle

Double Competitive Immunodetection of Small Analyte: Realization for Highly Sensitive Lateral Flow Immunoassay of Chloramphenicol

by Dmitriy V. Sotnikov, Lyubov V. Barshevskaya, Anastasia V. Bartosh, Anatoly V. Zherdev and Boris B. Dzantiev

Biosensors 2022, 12(5), 343; https://doi.org/10.3390/bios12050343 - 17 May 2022

Cited by 8 | Viewed by 2798

Abstract

A new scheme of reagents interaction for lateral flow immunoassay (LFIA) is proposed, which combines the features of competitive and sandwich assay and provides highly sensitive detection of low-molecular-weight analytes. Namely, the antigen in the sample interferes with the formation of the antibody [...] Read more.

A new scheme of reagents interaction for lateral flow immunoassay (LFIA) is proposed, which combines the features of competitive and sandwich assay and provides highly sensitive detection of low-molecular-weight analytes. Namely, the antigen in the sample interferes with the formation of the antibody (on the membrane)–hapten-protein–antibody (on the nanoparticle-marker) complex, competing with hapten-protein conjugate in both reactions. The proposed scheme was modelled using COPASI software, with a prediction of limit of detection (LOD) decrease by one order of magnitude compared to the standard competitive LFIA. This feature was experimentally confirmed for the detection of chloramphenicol (CAP) in honey. When tested in spiked honey, the visual LOD was 50 ng/mL for the common scheme and 5 ng/mL for the proposed scheme. Instrumental LOD was 300 pg/mL (1.2 µg/kg in conversion per sample weight of honey) in the standard scheme and 20 pg/mL (80 ng/kg in conversion per sample weight of honey) in the proposed scheme. Full article

(This article belongs to the Special Issue Immunosensors and Immunoassays for Environmental, Agricultural and Food Safety Applications)

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Scheme of the (a) standard and (b) proposed alternative competitive LFIAs. 1—Gold nanoparticles; 2—antigen in the sample; 3—antibodies against the antigen; 4—carrier protein; 5—antigen conjugated with carrier protein; 6—sample application membrane; 7—conjugate application membrane; 8—working nitrocellulose membrane; 9—analytical zone; 10—control zone; 11—final adsorbing membrane. Full article ">Figure 2
Dependence of the concentration of the detected complex in the absence of the analyte in (1) the proposed double competitive LFIA and (2) standard competitive LFIA. Model parameters: T = 30 s; t = 300 s; kai = 106 1/(M × s); kdi = 10−4 1/s.; [A]0 = 0 M. 1—[C]0 = 10 nM; [R]0 = 1 nM; 2—[R]0 = 6.2 nM. Full article ">Figure 3
(a) Theoretical calibration curves for (1) double competitive LFIA and (2) standard competitive LFIA. Model parameters: T = 30 s; t = 300 s; kai = 106 1/(M × s); kdi = 10−4 1/s. 1—[C]0 = 10 nM; [P]0 = 20 nM; [R]0 = 1 nM; 2—[P]0 = 20 nM; [R]0 = 0.62 nM. (b) Color intensity in the analytical zones of test strips (from Figure 5) for the determination of CAP in the (1) standard scheme of competitive LFIA and (2) proposed scheme of double competitive LFIA (b). Full article ">Figure 4
Dependence of the color intensity of the analytical zones on the concentration of antibodies when conjugated with a label in the standard competitive LFIA scheme in the absence of the analyte. Full article ">Figure 5
LFIA of CAP by (a) standard competitive scheme and (b) double competitive scheme. The appearance of test strips after the assays. Full article ">Figure 6
LFIA of CAP in honey by (a) standard competitive scheme and (b) double competitive scheme. The appearance of test strips after the assays. Full article ">Figure 7
Color intensity in the analytical zones of test strips (from <a href="#biosensors-12-00343-f006" class="html-fig">Figure 6</a>) for the determination of CAP: (1) in the standard scheme of competitive LFIA; (2) in the proposed scheme of double competitive LFIA. Full article ">

33 pages, 8375 KiB

Open AccessReview

Targeted Molecular Imaging Probes Based on Magnetic Resonance Imaging for Hepatocellular Carcinoma Diagnosis and Treatment

by Dongxu Zhao, Jian Cao, Lei Zhang, Shaohua Zhang and Song Wu

Biosensors 2022, 12(5), 342; https://doi.org/10.3390/bios12050342 - 17 May 2022

Cited by 15 | Viewed by 3896

Abstract

Hepatocellular carcinoma (HCC) is the sixth most commonly malignant tumor and the third leading cause of cancer-related death in the world, and the early diagnosis and treatment of patients with HCC is core in improving its prognosis. The early diagnosis of HCC depends [...] Read more.

Hepatocellular carcinoma (HCC) is the sixth most commonly malignant tumor and the third leading cause of cancer-related death in the world, and the early diagnosis and treatment of patients with HCC is core in improving its prognosis. The early diagnosis of HCC depends largely on magnetic resonance imaging (MRI). MRI has good soft-tissue resolution, which is the international standard method for the diagnosis of HCC. However, MRI is still insufficient in the diagnosis of some early small HCCs and malignant nodules, resulting in false negative results. With the deepening of research on HCC, researchers have found many specific molecular biomarkers on the surface of HCC cells, which may assist in diagnosis and treatment. On the other hand, molecular imaging has progressed rapidly in recent years, especially in the field of cancer theranostics. Hence, the preparation of molecular imaging probes that can specifically target the biomarkers of HCC, combined with MRI testing in vivo, may achieve the theranostic purpose of HCC in the early stage. Therefore, in this review, taking MR imaging as the basic point, we summarized the recent progress regarding the molecular imaging targeting various types of biomarkers on the surface of HCC cells to improve the theranostic rate of HCC. Lastly, we discussed the existing obstacles and future prospects of developing molecular imaging probes as HCC theranostic nanoplatforms. Full article

(This article belongs to the Special Issue Advances in Nanomedicines for Disease Diagnosis and Therapeutics)

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19 pages, 3018 KiB

Open AccessArticle

Solving Color Reproducibility between Digital Devices: A Robust Approach of Smartphones Color Management for Chemical (Bio)Sensors

by Pablo Cebrián, Leticia Pérez-Sienes, Isabel Sanz-Vicente, Ángel López-Molinero, Susana de Marcos and Javier Galbán

Biosensors 2022, 12(5), 341; https://doi.org/10.3390/bios12050341 - 17 May 2022

Cited by 5 | Viewed by 3606

Abstract

In the past twelve years, digital image colorimetry (DIC) on smartphones has acquired great importance as an alternative to the most common analytical techniques. This analysis method is based on fast, low-cost, and easily-accessible technology, which can provide quantitative information about an analyte [...] Read more.

In the past twelve years, digital image colorimetry (DIC) on smartphones has acquired great importance as an alternative to the most common analytical techniques. This analysis method is based on fast, low-cost, and easily-accessible technology, which can provide quantitative information about an analyte through the color changes of a digital image. Despite the fact that DIC is very widespread, it is not exempt from a series of problems that are not fully resolved yet, such as variability of the measurements between smartphones, image format in which color information is stored, power distribution of the illuminant used for the measurements, among others. This article proposes a methodology for the standardization and correction of these problems using self-developed software, together with the use of a 3D printed light box. This methodology is applied to three different colorimetric analyses using different types and brands of smartphones, proving that comparable measurements between devices can be achieved. As color can be related to many target analytes, establishing this measurement methodology can lead to new control analysis applicable to diverse sectors such as alimentary, industrial, agrarian, or sanitary. Full article

(This article belongs to the Special Issue Smartphone-Based Sensors for Biomedical Applications)

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The self-developed graph shows the number of publications related to the use of smartphones for analytical purposes by year. The data was compiled by searching the keywords “Smartphone analytical determinations” in the Google Scholar Research Gate. The graph shows a significant increase in the published articles in the last twelve years. Full article ">Figure 2
Scheme of the color measurement system used for this article. First, the LED strip is accommodated inside the light box. Second, the complementary piece is mounted on the upper part of the light box. Finally, the color sample is placed behind the light box and the photography is taken with the smartphone. Full article ">Figure 3
Flowchart for the correction of color samples. The methodology is based on a four-step process: (1) Initial evaluation of the color samples using CIE∆E2000, (2) Correction matrices generation with the Python-based software, (3) Color calibration by applying the matrices generated to the color samples, (4) Application of the methodology and matrices in real samples. Full article ">Figure 4
Normalized spectral power distribution of four different illuminants with respect to their maximum wavelength. The individual spectral power distribution of the illuminants is compared with the D50 Illuminant represented at the back of the graphic. Full article ">Figure 5
Box and Whisker plot of 5 RAL samples chosen randomly, associated with their RGB values. The lighter colors are the RGB values before the correction and the darker ones are after the correction. (a) Red channel values of five samples before/after the correction. (b) Green channel values of five samples before/after the correction. (c) Blue channel values of five samples before/after the correction. Full article ">Figure 6
Calibration of 12 solutions of different concentrations of peroxide hydrogen. The plot was adjusted to a second-degree polynomial equation. Full article ">Figure 7
pH calibration of 12 solutions in the range of 2 to 14 in pH. This plot shows the color transition for the PanReac AppliChem®pH strips between the pH values measured with the Xiaomi Redmi 6A Smartphone. Full article ">Figure 8
pH measurements with a Xiaomi Redmi 6A Smartphone. (a) Logistic function of the color measurements. (b) Linearized form of the logistic function for the color measurements. For the best-linearized fit, the values of pH 2, 3, 4, and 14 were discarded. Full article ">

12 pages, 3382 KiB

Open AccessArticle

Bead Number Effect in a Magnetic-Beads-Based Digital Microfluidic Immunoassay

by Wensyang Hsu, Yu-Teng Shih, Meng-Shiue Lee, Hong-Yuan Huang and Wan-Ning Wu

Biosensors 2022, 12(5), 340; https://doi.org/10.3390/bios12050340 - 16 May 2022

Cited by 13 | Viewed by 3990

Abstract

In a biomedical diagnosis with a limited sample volume and low concentration, droplet-based microfluidics, also called digital microfluidics, becomes a very attractive approach. Previously, our group developed a magnetic-beads-based digital microfluidic immunoassay with a bead number of around 100, requiring less than 1 [...] Read more.

In a biomedical diagnosis with a limited sample volume and low concentration, droplet-based microfluidics, also called digital microfluidics, becomes a very attractive approach. Previously, our group developed a magnetic-beads-based digital microfluidic immunoassay with a bead number of around 100, requiring less than 1 μL of sample volume to achieve a pg/mL level limit of detection (LOD). However, the bead number in each measurement was not the same, causing an unstable coefficient of variation (CV) in the calibration curve. Here, we investigated whether a fixed number of beads in this bead-based digital microfluidic immunoassay could provide more stable results. First, the bead screening chips were developed to extract exactly 100, 49, and 25 magnetic beads with diameters of less than 6 μm. Then, four calibration curves were established. One calibration curve was constructed by using varying bead numbers (50–160) in the process. The other three calibration curves used a fixed number of beads, (100, 49, and 25). The results indicated that the CVs for a fixed number of beads were evidently smaller than the CVs for varying bead numbers, especially in the range of 1 pg/mL to 100 pg/mL, where the CVs for 100 beads were less than 10%. Furthermore, the calculated LOD, based on the composite calibration curves, could be reduced by three orders, from 3.0 pg/mL (for the unfixed bead number) to 0.0287 pg/mL (for 100 beads). However, when the bead numbers were too high (more than 500) or too low (25 or fewer), the bead manipulation for aggregation became more difficult in the magnetic-beads-based digital microfluidic immunoassay chip. Full article

(This article belongs to the Special Issue Biosensors Based on Microfluidic Devices)

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Operating concept: (a) obtaining the specified magnetic bead number on a bead screening chip; (b) immunoassay process on the chip with a fixed number of magnetic beads; (c) beads’ aggregation for fluorescence intensity measurement at the detection area. Full article ">Figure 2
Obtaining the specified bead number on the bead screening chip. (a) Move the bead droplet and magnet to fill the wells with beads: (a1) Drag the bead droplet towards the wells; (a2) Move the droplet and magnet backward and forward to fill the wells with beads. (b) Remove excessive beads with liquid by a pipet. (c) Every well was filled with exact one bead; (d) Use a magnet to attract the beads to the droplet top surface and then retrieve the droplet with all beads by a pipet. Full article ">Figure 3
The digital microfluidic chip for immunoassay. Full article ">Figure 4
Comparison of the calibration curves obtained by an unfixed number of magnetic beads (50–160) and three fixed numbers of magnetic beads (100, 49, and 25). Full article ">Figure 5
Comparison of the CV values of an unfixed number of magnetic beads and three different fixed numbers of magnetic beads at different concentrations. Full article ">Figure 6
Fluorescence intensity distribution and composite calibration curves for the unfixed number of magnetic beads and for the other three with fixed numbers of magnetic beads at the low concentrations of 0.0 pg/mL, 0.1 pg/mL, and 1.0 pg/mL. (a) The measured fluorescence intensity distribution overlaps when the number of magnetic beads is unfixed (50–160). When the fixed numbers of magnetic beads are (b) 100 beads, (c) 49 beads, or (d) 25 beads at concentrations of 0.0 pg/mL, 0.1 pg/mL, and 1.0 pg/mL, respectively, the fluorescence intensity distributions do not overlap. The LODs for (a) variable beads, (b) 100 beads, (c) 49 beads, and (d) 25 beads are 3.0 pg/mL, 0.0287 pg/mL, 0.0255 pg/mL, and 0.0508 pg/mL, respectively. n = 3. Full article ">Figure 7
Microscopic images of successful aggregation at bead numbers of (a) 25, (b) 49, and (c) 100. Full article ">Figure 8
Beads aggregation issue with too few or too many beads. (a) 25 magnetic beads: (a1) Some magnetic beads cannot be aggregated; (a2) The droplet with 25 magnetic beads, black shadow was the magnet; (a3) Some magnetic beads could not be aggregated. (b) More than 500 magnetic beads: (b1) Some magnetic beads were stuck and could not be moved; (b2) The droplet with more than 500 beads; (b3) Some successfully aggregated beads. Full article ">

23 pages, 6629 KiB

Open AccessEditor’s ChoiceArticle

Portable Respiration Monitoring System with an Embroidered Capacitive Facemask Sensor

by Mitar Simić, Adrian K. Stavrakis, Ankita Sinha, Velibor Premčevski, Branko Markoski and Goran M. Stojanović

Biosensors 2022, 12(5), 339; https://doi.org/10.3390/bios12050339 - 15 May 2022

Cited by 21 | Viewed by 4431

Abstract

Respiration monitoring is a very important indicator of health status. It can be used as a marker in the recognition of a variety of diseases, such as sleep apnea, asthma or cardiac arrest. The purpose of the present study is to overcome limitations [...] Read more.

Respiration monitoring is a very important indicator of health status. It can be used as a marker in the recognition of a variety of diseases, such as sleep apnea, asthma or cardiac arrest. The purpose of the present study is to overcome limitations of the current state of the art in the field of respiration monitoring systems. Our goal was the development of a lightweight handheld device with portable operation and low power consumption. The proposed approach includes a textile capacitive sensor with interdigitated electrodes embroidered into the facemask, integrated with readout electronics. Readout electronics is based on the direct interface of the capacitive sensor and a microcontroller through just one analog and one digital pin. The microcontroller board and sensor are powered by a smartphone or PC through a USB cable. The developed mobile application for the Android™ operating system offers reliable data acquisition and acts as a bridge for data transfer to the remote server. The embroidered sensor was initially tested in a humidity-controlled chamber connected to a commercial impedance analyzer. Finally, in situ testing with 10 volunteering subjects confirmed stable operation with reliable respiration monitoring. Full article

(This article belongs to the Special Issue Electrochemical (Bio)Sensors and Energy Autonomous Sensing System)

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9 pages, 1295 KiB

Open AccessCommunication

Establishment and Comparative Analysis of Enzyme-Linked Immunoassay and Time-Resolved Fluoroimmunoassay for the Determination of Trace Quinclorac in Environment

by Xue Liu, Xiuzhai Chen, Xu Zhu, Qing Lin, Xi Pan, Xiaolei Tan, Yongfeng Guo, Jun Qiu and Song Fang

Biosensors 2022, 12(5), 338; https://doi.org/10.3390/bios12050338 - 14 May 2022

Cited by 4 | Viewed by 2346

Abstract

As a common herbicide in farmland, there has been wide concern over quinclorac residue because of its potential risks to the environment and human health. For the detection and monitoring of quinclorac residue in the environment, enzyme-linked immunoassay (ELISA) and time-resolved fluoroimmunoassay (TRFIA) [...] Read more.

As a common herbicide in farmland, there has been wide concern over quinclorac residue because of its potential risks to the environment and human health. For the detection and monitoring of quinclorac residue in the environment, enzyme-linked immunoassay (ELISA) and time-resolved fluoroimmunoassay (TRFIA) were established. The half-maximal inhibition concentrations (IC₅₀) of ELISA and TRFIA were 0.169 mg/L and 0.087 mg/L with a linear range (IC₂₀–IC₈₀) of 0.020–1.389 mg/L and 0.004–1.861 mg/L, respectively. Compared with ELISA, the limit of detection (LOD, IC₂₀) and IC₅₀ of TRFIA improved approximately 5-fold and 2-fold. The cross-reaction rates for the quinclorac analogs were less than 2%. The average recoveries of quinclorac in river water, paddy water, paddy soil, and brown rice samples were 77.3–106.1%, with RSDs of 1.7–12.5%. More importantly, the results of the two methods were consistent with that of the referenced method of UPLC-MS/MS (R² > 0.98). ELISA and TRFIA both showed good detection performance and could meet the requirements of the quantitative determination of quinclorac. Therefore, the proposed ELISA and TRFIA could be applied to the rapid and sensitive detection and monitoring of quinclorac residue in the environment. Full article

(This article belongs to the Special Issue Immunosensors and Immunoassays for Environmental, Agricultural and Food Safety Applications)

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16 pages, 4513 KiB

Open AccessArticle

Multilayered Mesoporous Composite Nanostructures for Highly Sensitive Label-Free Quantification of Cardiac Troponin-I

by Mohsen Saeidi, Mohammad Ali Amidian, Sana Sheybanikashani, Hossein Mahdavi, Homayoon Alimohammadi, Leila Syedmoradi, Fatemeh Mohandes, Ali Zarrabi, Elnaz Tamjid, Kobra Omidfar and Abdolreza Simchi

Biosensors 2022, 12(5), 337; https://doi.org/10.3390/bios12050337 - 14 May 2022

Cited by 15 | Viewed by 3324

Abstract

Cardiac troponin-I (cTnI) is a well-known biomarker for the diagnosis and control of acute myocardial infarction in clinical practice. To improve the accuracy and reliability of cTnI electrochemical immunosensors, we propose a multilayer nanostructure consisting of Fe₃O₄-COOH labeled anti-cTnI [...] Read more.

Cardiac troponin-I (cTnI) is a well-known biomarker for the diagnosis and control of acute myocardial infarction in clinical practice. To improve the accuracy and reliability of cTnI electrochemical immunosensors, we propose a multilayer nanostructure consisting of Fe₃O₄-COOH labeled anti-cTnI monoclonal antibody (Fe₃O₄-COOH-Ab₁) and anti-cTnI polyclonal antibody (Ab₂) conjugated on Au-Ag nanoparticles (NPs) decorated on a metal–organic framework (Au-Ag@ZIF-67-Ab₂). In this design, Fe₃O₄-COOH was used for separation of cTnI in specimens and signal amplification, hierarchical porous ZIF-67 extremely enhanced the specific surface area, and Au-Ag NPs synergically promoted the conductivity and sensitivity. They were additionally employed as an immobilization platform to enhance antibody loading. Electron microscopy images indicated that Ag-Au NPs with an average diameter of 1.9 ± 0.5 nm were uniformly decorated on plate-like ZIF-67 particles (with average size of 690 nm) without any agglomeration. Several electrochemical assays were implemented to precisely evaluate the immunosensor performance. The square wave voltammetry technique exhibited the best performance with a sensitivity of 0.98 mA mL cm⁻² ng⁻¹ and a detection limit of 0.047 pg mL⁻¹ in the linear range of 0.04 to 8 ng mL⁻¹. Full article

(This article belongs to the Special Issue Advances and New Perspectives in Micro-Nanofabricated Sensors for Bioanalysis)

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FE-SEM images of (a) ZIF-67, (b) Au@ZIF-67, (c) Ag@ZIF-67, and (d) Au-Ag@ZIF-67. HR-TEM of (e) and (f) ZIF-67 (inset of (f) shows the corresponding SAED pattern), and (g–i) Au-Ag NP@ZIF-67 (insets of (h,i) show the corresponding nanoparticle size distribution and FFT pattern, respectively). Full article ">Figure 2
EDS mapping of (a) ZIF-67 and (b) Au-Ag@ZIF-67. Full article ">Figure 3
(a) XRD patterns of ZIF-67 and Au-Ag@ZIF-67, (b) FTIR spectrum of ZIF-67, (c–g) XPS spectra of ZIF-67, (h) N2 adsorption/desorption isotherms, and (i) Pore size distributions of samples. Full article ">Figure 4
Schematic illustration of the procedure used for preparing the cTnI immunosensors. Full article ">Figure 5
(a,c) CV curves; (b,d) EIS characterization of the stepwise modified SPCE. All experiments were implemented in a solution of 5 mM [Fe(CN)6]3/4- in 0.01 M PBS containing 0.1 M KCl. Scan rate was 50 mV s−1. ((i): Ab2/Au-Ag@ZIF-67/SPCE, (ii): BSA/Ab2/Au-Ag@ZIF-67/SPCE, (iii): Fe3O4-COOH-Ab1 added to BSA/Ab2/Au-Ag@ZIF-67/SPCE, (iv): Fe3O4-COOH-Ab1-cTnI/BSA/Ab2/Au-Ag@ZIF-67/SPCE). Full article ">Figure 6
(a) CV curves at the scan rate of 50 mV s−1; (b) EIS curves for various cTnI concentrations from 0 to 10 ng mL−1. (c,d) the corresponding calibration curves with the linear fitting equations for (a,b), respectively. All experiments were implemented in a solution of 5 mM [Fe(CN)6]3-/4- in 0.01 M PBS containing 0.1 M KCl. cTnI concentrations increased in the following order (i): 0, (ii): 0.04, (iii): 0.1, (iv): 0.2, (v): 0.3, (vi): 0.4, (vii): 0.5, (viii): 0.6, (ix): 0.7, (x): 0.8, (xi): 0.9, (xii): 1, (xiii): 2, (xiv): 3, (xv): 4, (xvi): 5, (xvii): 6, (xviii): 7, (xix): 8, (xx): 9, and (xxi): 10 ng mL−1. Full article ">Figure 7
(a) DPV curves at the modulation amplitude of 0.25 V; (b) SWV curves at the frequency of 15 Hz. (c,d) the corresponding calibration curves with the linear fitting equations for (a,b), respectively. All experiments were implemented in a solution of 5 mM [Fe(CN)6]3-/4- in 0.01 M PBS containing 0.1 M KCl. cTnI concentrations increased in the following order (i): 0, (ii): 0.04, (iii): 0.1, (iv): 0.2, (v): 0.3, (vi): 0.4, (vii): 0.5, (viii): 0.6, (ix): 0.7, (x): 0.8, (xi): 0.9, (xii): 1, (xiii): 2, (xiv): 3, (xv): 4, (xvi): 5, (xvii): 6, (xviii): 7, (xix): 8, (xx): 9, and (xxi): 10 ng mL−1. Full article ">

20 pages, 4217 KiB

Open AccessReview

Assessment of Nanoparticle-Mediated Tumor Oxygen Modulation by Photoacoustic Imaging

by Maharajan Sivasubramanian and Leu-Wei Lo

Biosensors 2022, 12(5), 336; https://doi.org/10.3390/bios12050336 - 13 May 2022

Cited by 8 | Viewed by 3698

Abstract

Photoacoustic imaging (PAI) is an invaluable tool in biomedical imaging, as it provides anatomical and functional information in real time. Its ability to image at clinically relevant depths with high spatial resolution using endogenous tissues as contrast agents constitutes its major advantage. One [...] Read more.

Photoacoustic imaging (PAI) is an invaluable tool in biomedical imaging, as it provides anatomical and functional information in real time. Its ability to image at clinically relevant depths with high spatial resolution using endogenous tissues as contrast agents constitutes its major advantage. One of the most important applications of PAI is to quantify tissue oxygen saturation by measuring the differential absorption characteristics of oxy and deoxy Hb. Consequently, PAI can be utilized to monitor tumor-related hypoxia, which is a crucial factor in tumor microenvironments that has a strong influence on tumor invasiveness. Reactive oxygen species (ROS)-based therapies, such as photodynamic therapy, radiotherapy, and sonodynamic therapy, are oxygen-consuming, and tumor hypoxia is detrimental to their efficacy. Therefore, a persistent demand exists for agents that can supply oxygen to tumors for better ROS-based therapeutic outcomes. Among the various strategies, NP-mediated supplemental tumor oxygenation is especially encouraging due to its physio-chemical, tumor targeting, and theranostic properties. Here, we focus on NP-based tumor oxygenation, which includes NP as oxygen carriers and oxygen-generating strategies to alleviate hypoxia monitored by PAI. The information obtained from quantitative tumor oxygenation by PAI not only supports optimal therapeutic design but also serves as a highly effective tool to predict therapeutic outcomes. Full article

(This article belongs to the Special Issue Multimodal, Multifunctional Biosensors or Imaging Systems and Their Biomedical Applications)

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Schematic illustration of PAI. Full article ">Figure 2
(a) The diagram of dosage regimen. (b) Inhibition of 4T1 tumor growth by PDT and IDO inhibitor. Tumor-bearing mice were intratumorally injected with oxygen-saturated PF-PEG@Ce6@NLG 919, and the tumor sites were illuminated (660 nm, 55 W/cm2). (c) Photograph of the tumors removed on day 14. (d) The weight of the tumor treated with different formulations on the last day. (e) TUNEL staining of tumor sections. The green light spots represent DNA damage tagged on FITC; the blue represents the nucleus labeled with DAPI. (f) The body weight of the mice. p values: ** p < 0.01, *** p < 0.001, one-way ANOVA, n = 5. (g) Immunofluorescence staining of tumor sections to detect whether the PF-PEG group could improve hypoxia in vivo. The nucleus and the anoxic region were stained with DAPI (blue) and SOSG (green), respectively. Reproduced with permission [<a href="#B74-biosensors-12-00336" class="html-bibr">74</a>]. Copyright 2019, Elsevier B.V. Full article ">Figure 3
(a) Schematic illustration of the synthesis procedures and antitumor mechanism of OHZ NP. (b) Schematic illustration of OHZ NP for tumor treatment. (c) Relative tumor volume curves of mice treated with various treatments, (d) tumor weights of mice at the 14th day after the treatments, and (e) the photographs of mice and tumors in different groups at the end of treatments of the subcutaneous tumor treatment group. (f) Relative tumor volume curves of mice treated with various treatments, (g) tumor weights of mice at the 14th day after the treatments, and (h) the photographs of mice and tumors in different groups at the end of treatments of the deep-seated tumor treatment group mimicked by 2 cm chicken slice blocking. p values were calculated via ANOVA (*** p < 0.001). Fluorescence images of (i) subcutaneous tumor slices and (j) deep-seated tumor slices after being stained by H&E and TUNEL. Reproduced with permission [<a href="#B86-biosensors-12-00336" class="html-bibr">86</a>]. Copyright 2021, American Chemical Society. Full article ">Figure 4
(a) Relative tumor growth curves recorded during treatment. The dosage of ICG/AuNR@BCNP in mice was equivalent to ICG 1.0 mg/kg and Au 0.76 mg/kg. (b) Weight and photograph of isolated tumor at the end of treatment. (c) Immunofluorescence staining of tumor sections with TUNEL, anti-HIF-1α, and anti-CD31 antibody. Scale bar: 50 or 100 μm. Corresponding semiquantitative analysis of (d) the apoptotic index and (e) HIF-1α and (f) CD31 positive areas (mean ± SD, n = 3–5, * p < 0.05, ** p < 0.01, *** p < 0.001). (g) H&E and ki67 staining of tumor sections. Scale bars: 1 mm for low magnification, 100 μm for high magnification. Reproduced with permission [<a href="#B95-biosensors-12-00336" class="html-bibr">95</a>]. Copyright 2020, American Chemical Society. Full article ">Figure 5
In vivo combined chemo-PDT treatment with H-MnO2-PEG/C&D. (a) Representative immunofluorescence images of 4T1 tumor slices collected from untreated control mice and mice 6 h and 12 h post i.v. injection with H-MnO2-PEG/C&D. The nuclei, blood vessels, and hypoxic areas were stained with DAPI (blue), anti-CD31 antibody (red), and anti-pimonidazole antibody (green), respectively (three mice per group). (b) Quantification of hypoxia areas in tumors at different time points post injection of our NP. (c) Tumor growth curves of different groups of mice after various treatments indicated. Error bars were based on standard errors of the mean (SEM) (six mice per group). (d) Average weight of tumors collected from mice at day 14 post initiation of various treatments. The predicted addictive effect was calculated by multiplying the tumor growth inhibition ratios of group 4 (PDT alone) and group 5 (chemotherapy alone). (e) H&E-stained tumor slices collected from mice post various treatments indicated. p values in (c,d) were calculated by Tukey’s post-test (*** p < 0.001, ** p < 0.01, or * p < 0.05). Reproduced with permission [<a href="#B100-biosensors-12-00336" class="html-bibr">100</a>]. Copyright 2017, Nature publishing group. Full article ">Figure 6
(a) Representative PA images of B16 tumors on mice showing signals of oxygenated hemoglobin (λ = 850 nm) before/after i.v. injection of various formulations. (b) The corresponding quantification of the tumor vascular saturated O2 levels (sO2) calculated from (a). (c) Immunofluorescence staining of tumor sections showing the expression of HIF-1α after i.v. injection of various formulations (d) Quantitative analysis of HIF-1α positive areas for each group in (c) by using the ImageJ software (n = 5). (*** p < 0.001, ** p < 0.01). Reproduced with permission [<a href="#B108-biosensors-12-00336" class="html-bibr">108</a>]. Copyright 2021, Elsevier B.V. Full article ">

12 pages, 2107 KiB

Open AccessArticle

Functionalization of Glucose Oxidase in Organic Solvent: Towards Direct Electrical Communication across Enzyme-Electrode Interface

by Vygailė Dudkaitė and Gintautas Bagdžiūnas

Biosensors 2022, 12(5), 335; https://doi.org/10.3390/bios12050335 - 13 May 2022

Cited by 8 | Viewed by 3307

Abstract

Enzymatic biosensors based on glucose oxidase has been proven to be one of the effective strategies for the detection of glucose and contributed to health improvements. Therefore, research and debates to date are ongoing in an attempt to find the most effective way [...] Read more.

Enzymatic biosensors based on glucose oxidase has been proven to be one of the effective strategies for the detection of glucose and contributed to health improvements. Therefore, research and debates to date are ongoing in an attempt to find the most effective way to detect this analyte using this enzyme as the recognition center. The 3rd generation biosensors using direct electron transfer (DET) type enzymes are a great way towards practical devices. In this work, we developed a simple method for the functionalization of glucose oxidase with redoxable ferrocene groups in chloroform. The enzyme retained its activity after storage in this organic solvent and after the functionalization procedures. This enzyme functionalization strategy was employed to develop the biosensing monolayer-based platforms for the detection of glucose utilizing the quasi-DET mechanism. As a result of an electrochemical regeneration of the catalytic center, the formation of harmful H₂O₂ is minimized during enzymatic electrocatalysis. Full article

(This article belongs to the Special Issue Electrochemistry and Spectroscopy-Based Biosensors)

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Spectroscopic characterization of Fc-GOx: (a) CD spectra of the Fc-GOx, unaffected (initial) GOx and GOx after its exposure in CHCl3 samples (c = 1 mg mL−1) and (b) UV–Vis (c = 0.25 mg mL−1); (c) the measured hydrodynamic diameters of Fc-GOx, initial GOx, and GOx after its exposure in CHCl3 (c = 1 mg mL−1). All the samples were dissolved in the PPB pH 7.0 solution. Full article ">Figure 2
AFM analysis of the modified gold substrates: (a) schematic presentation of the self-assembly monolayer of Fc-GOx deposition on Au; (b) AFM picture of GOx/MBA/Au at dimensions of 10 × 10 μm; (c) AFM picture of Fc-GOx/MBA/Au at dimensions of 10 × 10 μm; (d) AFM picture of Fc-GOx/MBA/Au at dimensions of 200 × 200 nm; (e) AFM picture of the surface of bare Au at dimensions of 200 × 200 nm; (f) grain diameters distributions on the Fc-GOx/MBA/Au surface at dimensions of 200 × 200 nm. Full article ">Figure 3
Electrochemical analysis of the GOx/MBA/Au and Fc-GOx/MBA/Au electrodes: (a) cyclic voltametric (CV) analysis of these electrodes in PPB pH 7.0 at 20 mV s−1 (inset: CV of FcCHO in acetonitrile with Et4NBF4 as a supporting electrolyte); (b) CVs of Fc-GOx/MBA/Au under varying glucose concentration presence atmospheric oxygen; (c) CVs of Fc-GOx/MBA/Au in PPB without oxygen; (d) CVs of GOx/MBA/Au under varying glucose concentration presence atmospheric oxygen; (e) CVs of GOx/MBA/Au without oxygen; (f) CVs of MBA/Au under varying glucose concentration; (g) current densities responses on the concentrations of glucose at 0.3 V vs. Ag/AgCl; (h) the magnified responses from 0 to 0.5 mM of glucose; (i) Lineweaver–Burk linearity test of all these responses. Full article ">Scheme 1
Schematic drawing of glucose oxidation and hole hopping into Fc-functionalized GOx and the electrical communication between the cofactor and the Au surface. Full article ">

14 pages, 2825 KiB

Open AccessEditor’s ChoiceArticle

Field-Effect Capacitors Decorated with Ligand-Stabilized Gold Nanoparticles: Modeling and Experiments

by Arshak Poghossian, Tobias Karschuck, Patrick Wagner and Michael J. Schöning

Biosensors 2022, 12(5), 334; https://doi.org/10.3390/bios12050334 - 13 May 2022

Cited by 4 | Viewed by 2533

Abstract

Nanoparticles are recognized as highly attractive tunable materials for designing field-effect biosensors with enhanced performance. In this work, we present a theoretical model for electrolyte-insulator-semiconductor capacitors (EISCAP) decorated with ligand-stabilized charged gold nanoparticles. The charged AuNPs are taken into account as additional, nanometer-sized [...] Read more.

Nanoparticles are recognized as highly attractive tunable materials for designing field-effect biosensors with enhanced performance. In this work, we present a theoretical model for electrolyte-insulator-semiconductor capacitors (EISCAP) decorated with ligand-stabilized charged gold nanoparticles. The charged AuNPs are taken into account as additional, nanometer-sized local gates. The capacitance-voltage (C–V) curves and constant-capacitance (ConCap) signals of the AuNP-decorated EISCAPs have been simulated. The impact of the AuNP coverage on the shift of the C–V curves and the ConCap signals was also studied experimentally on Al–p-Si–SiO₂ EISCAPs decorated with positively charged aminooctanethiol-capped AuNPs. In addition, the surface of the EISCAPs, modified with AuNPs, was characterized by scanning electron microscopy for different immobilization times of the nanoparticles. Full article

(This article belongs to the Special Issue Biosensors in Nanotechnology)

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Schematic structure and shape of the depletion layer in p-Si for a bare EISCAP (a) and an EISCAP decorated with ligand-stabilized positively charged AuNPs (b); (c) electrical equivalent circuit of an AuNP-decorated EISCAP; and (d) local changes in the width of the depletion layer at the gate voltage (VG-NP), which is applied to the AuNP-decorated EISCAP in the ConCap mode to keep the working capacitance constant. RRE: resistance of the reference electrode; VG: gate voltage; VAC: alternating current voltage; CiNP, CsNP and CNP: gate-insulator, space-charge and total capacitances in an AuNP-covered region, respectively; Ci, Cs and C0 are the corresponding parameters for AuNP-free regions; φ0 and φNP: gate insulator-electrolyte interfacial potential in the AuNP-free and AuNP-covered regions. Full article ">Figure 2
(a) Simulated C–V curves of a bare, p-type EISCAP and an EISCAP decorated with positively charged AuNPs with different coverages n (from 0.25 to 0.9). The dashed curves illustrate the expected course of the overall equivalent capacitance of the EISCAP in the transition region from depletion to accumulation. (b) Capacitance changes (at a constant gate voltage of VG = 50 mV) and voltage shifts (at a constant capacitance of Ceq-dep = 30 nF) as a function of the AuNP coverage, evaluated from the C–V curves. Full article ">Figure 3
Calculated ConCap signal change (ΔVG-NP) of an AuNP-decorated EISCAP as a function of the AuNP coverage with n varying from 0.25 to 0.9. Full article ">Figure 4
Representative SEM images of an EISCAP surface decorated with AOT-AuNPs with immobilization times of 0.5 h (a), 1 h (b) and 2 h (c). Full article ">Figure 5
(a) Measured C–V curves of a bare EISCAP and an EISCAP decorated with positively charged AOT-AuNPs of different coverages n (for different times of immobilization between 0.5 and 2 h) with a zoomed graph of the depletion region. (b) Capacitance changes (at a constant gate voltage of −528 mV) and gate voltage shifts (at a constant capacitance of 37 nF) evaluated from the C–V curves as a function of the AuNP coverage. Full article ">Figure 6
Dynamic ConCap signal change of the EISCAP decorated with positively charged AuNPs of different coverages n, corresponding to AuNP immobilization times of 0.5 h, 1 h and 2 h. Full article ">

13 pages, 2322 KiB

Open AccessArticle

A Patient-Ready Wearable Transcutaneous CO₂ Sensor

by Juan Pedro Cascales, Xiaolei Li, Emmanuel Roussakis and Conor L. Evans

Biosensors 2022, 12(5), 333; https://doi.org/10.3390/bios12050333 - 13 May 2022

Cited by 17 | Viewed by 4633

Abstract

Continuously monitoring transcutaneous CO₂ partial pressure is of crucial importance in the diagnosis and treatment of respiratory and cardiac diseases. Despite significant progress in the development of CO₂ sensors, their implementation as portable or wearable devices for real-time monitoring remains under-explored. [...] Read more.

Continuously monitoring transcutaneous CO₂ partial pressure is of crucial importance in the diagnosis and treatment of respiratory and cardiac diseases. Despite significant progress in the development of CO₂ sensors, their implementation as portable or wearable devices for real-time monitoring remains under-explored. Here, we report on the creation of a wearable prototype device for transcutaneous CO₂ monitoring based on quantifying the fluorescence of a highly breathable CO₂-sensing film. The developed materials are based on a fluorescent pH indicator (8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt or HPTS) embedded into hydrophobic polymer matrices. The film’s fluorescence is highly sensitive to changes in CO₂ partial pressure in the physiological range, as well as photostable and insensitive to humidity. The device and medical-grade films are based on our prior work on transcutaneous oxygen-sensing technology, which has been extensively validated clinically. Full article

(This article belongs to the Special Issue Frontiers of Wearable Biosensors for Human Health Monitoring)

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Figure 1
(a) Wearable device and <math display="inline"><semantics> <mrow> <mi>C</mi> <msub> <mi>O</mi> <mn>2</mn> </msub> </mrow> </semantics></math>-sensing film for continuous transcutaneous monitoring of <math display="inline"><semantics> <mrow> <mi>p</mi> <mi>C</mi> <msub> <mi>O</mi> <mn>2</mn> </msub> </mrow> </semantics></math>. The film emission is excited via two (405 nm and 470 nm) high-intensity LED’s and sampled via a 500 nm long-pass filter and a PIN photodiode. (b) Optical spectra of the two different excitation LEDs and the <math display="inline"><semantics> <mrow> <mi>C</mi> <msub> <mi>O</mi> <mn>2</mn> </msub> </mrow> </semantics></math>-sensing dye emission, as shown in the inset. The addition of a 500 nm long-pass filter removes the LED emission. Full article ">Figure 2
(a) Chemical structures of ion pairs and polymer matrices: (HPTS)/(CTA)3, (HPTS)/(TOA)4, poly(methyl methacrylate)(PMMA), and poly(propyl methacrylate)(PPMA). The pH sensitivity of the ion pairs arises from the highlighted functional groups. (b) Emission spectra of (HPTS)/(CTA)3 in PPMA and (HPTS)/(TOA)4 in PPMA and PMMA under CO2 and N2 conditions. (c) Excitation spectra (collected at 570nm) of (HPTS)/(CTA)3 in PPMA and (HPTS)/(TOA)4 in PPMA and PMMA under CO2 and N2 conditions. (d) Moisture sensitivity of (HPTS)/(TOA)4 in PPMA and PMMA under CO2 and N2 conditions. (e) Photostability comparison of (HPTS)/(TOA)4 in PPMA and PMMA under air condition. Full article ">Figure 3
(a) Sensitivity of materials made of 240 μM or 480 μM (HPTS)/(TOA)4 in PPMA with the addition of 0%, 5%, 10%, 20%, and 40% (v/v) methanolic solution of TOAOH. (b) Photostability comparison of sensing films prepared from 240 μM (HPTS)/(TOA)4 in PPMA containing 5%, 10%, and 20% (v/v) TOAOH solution and 480 μM (HPTS)/(TOA)4 in PPMA with 20% (v/v) TOAOH solution under the air condition. (c) Moisture sensitivity of the material prepared from 240 μM (HPTS)/(TOA)4 in PPMA with 10% (v/v) TOAOH solution under CO2 and N2 conditions. Full article ">Figure 4
(a) Excitation spectra measured at 570 nm of the (HPTS)/(TOA)4 in the PPMA formulation exposed to different CO2 partial pressures. (b) Normalized R (between [0,1]) vs. CO2 partial pressure of a PPMA/white coating sample, showing a delayed diffusion of CO2 through the white coating (CO2 → white), which disappears at temperatures over 40 °C. The fluorescence ratio R measured with the wearable is highly sensitive to changes in CO2, with our prototypes showing a delayed response with respect to the reference <math display="inline"><semantics> <mrow> <mi>C</mi> <msub> <mi>O</mi> <mn>2</mn> </msub> </mrow> </semantics></math> sensor at (c) T = 25 °C, attributed to CO2 diffusion through the white scattering layer, vanishing when heating up to (d) T = 44 °C. (e) Normalized R vs. CO2 for the wearable at different temperatures, with the delayed response vanishing at higher temperatures. (f) Time delay (lag) between our prototype’s signal and the reference CO2 sensor as a function of temperature. Full article ">Figure 5
(a) Response of the film to changes in CO2, plotted along with a reference sensor’s CO2 readings. (b) Fit of two different calibration algorithms to the fluorescence ratio R, plotted as a function of the reference CO2. <math display="inline"><semantics> <mrow> <mi>F</mi> <mi>i</mi> <mi>t</mi> <mn>1</mn> </mrow> </semantics></math> considers a quadratic dependence on CO2, while <math display="inline"><semantics> <mrow> <mi>F</mi> <mi>i</mi> <mi>t</mi> <mn>2</mn> </mrow> </semantics></math> also considers a quadratic dependence on CO2, but with different coefficients depending on whether R (and hence, CO2) is increasing or decreasing. (c) Reference and estimated CO2 from our prototype, obtained with both algorithms. Full article ">

10 pages, 909 KiB

Open AccessCommunication

Two-Dimensional Ti₃C₂ MXene-Based Novel Nanocomposites for Breath Sensors for Early Detection of Diabetes Mellitus

by Anna Rudie, Anna Marie Schornack, Qiang Wu, Qifeng Zhang and Danling Wang

Biosensors 2022, 12(5), 332; https://doi.org/10.3390/bios12050332 - 13 May 2022

Cited by 11 | Viewed by 3329

Abstract

The rates of diabetes throughout the world are rising rapidly, impacting nearly every country. New research is focused on better ways to monitor and treat this disease. Breath acetone levels have been defined as a biomarker for diabetes. The development of a method [...] Read more.

The rates of diabetes throughout the world are rising rapidly, impacting nearly every country. New research is focused on better ways to monitor and treat this disease. Breath acetone levels have been defined as a biomarker for diabetes. The development of a method to monitor and diagnose diabetes utilizing breath acetone levels would provide a fast, easy, and non-invasive treatment option. An ideal material for point-of-care diabetes management would need to have a high response to acetone, high acetone selectivity, low interference from humidity, and be able to operate at room temperature. Chemiresistive gas sensors are a promising method for sensing breath acetone due to their simple fabrication and easy operation. Certain semiconductor materials in chemiresistive sensors can react to acetone in the air and produce changes in resistance that can be correlated with acetone levels. While these materials have been developed and show strong responses to acetone with good selectivity, most of them must operate at high temperatures (compared to RT), causing high power consumption, unstable device operation, and complex device design. In this paper, we systematically studied a series of 2-dimensional MXene-based nanocomposites as the sensing materials in chemiresistive sensors to detect 2.86 ppm of acetone at room temperature. Most of them showed great sensitivity and selectivity for acetone. In particular, the 1D/2D CrWO/Ti₃C₂ nanocomposite showed the best sensing response to acetone: nine times higher sensitivity than 1D KWO nanowires. To determine the sensing selectivity, a CrWO/Ti₃C₂ nanocomposite-based sensor was exposed to various common vapors in human breath. The result revealed that it has excellent selectivity for acetone, and far lower responses to other vapors. All these preliminary results indicate that this material is a promising candidate for the creation of a point-of-care diabetes management device. Full article

(This article belongs to the Special Issue Nanomaterials and Nanostructure Devices for Biosensing)

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16 pages, 3700 KiB

Open AccessArticle

Electrochemical Biosensor Using Nitrogen-Doped Graphene/Au Nanoparticles/DNAzyme for Ca²⁺ Determination

by Zhixue Yu, Hui Wang, Yiguang Zhao, Fan Zhang, Xiangfang Tang and Benhai Xiong

Biosensors 2022, 12(5), 331; https://doi.org/10.3390/bios12050331 - 12 May 2022

Cited by 6 | Viewed by 3082

Abstract

An electrochemical biosensor for detecting Ca²⁺ concentration was proposed using glass carbon electrodes (GCEs) modified with nitrogen-doped graphene (NGR), gold nanoparticles (AuNPs) and DNAzyme. The resistance signal was amplified through two methods: electrochemical reduction of AuNPs on the NGR surface to increase [...] Read more.

An electrochemical biosensor for detecting Ca²⁺ concentration was proposed using glass carbon electrodes (GCEs) modified with nitrogen-doped graphene (NGR), gold nanoparticles (AuNPs) and DNAzyme. The resistance signal was amplified through two methods: electrochemical reduction of AuNPs on the NGR surface to increase the specific surface area of the electrode and strengthen the adsorption of DNAzyme; and increasement of the DNAzyme base sequence. The process of electrode modification was characterized by scanning electron microscopy, Raman spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Experimental parameters’ influence, such as the deposition time of gold nanoparticles and the detection time, were assessed by electrochemical methods. The linear ranges of the electrochemical biosensor were in the range from 5 × 10⁻⁶ to 5 × 10⁻⁵ and 5 × 10⁻⁵ to 4 × 10⁻⁴ M, with a detection limit of 3.8 × 10⁻⁶ M. The concentration of Ca²⁺ in the serum of dairy cows was determined by the biosensor with satisfactory results, which could be potentially used to diagnose subclinical hypocalcemia. Full article

(This article belongs to the Special Issue Nano/Micro Technologies for Biosensors: A Themed Issue in Honor of Prof. Dr. Chung-Chiun Liu)

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14 pages, 3684 KiB

Open AccessEditor’s ChoiceArticle

A Digital Microfluidic Device Integrated with Electrochemical Impedance Spectroscopy for Cell-Based Immunoassay

by Yuqian Zhang and Yuguang Liu

Biosensors 2022, 12(5), 330; https://doi.org/10.3390/bios12050330 - 12 May 2022

Cited by 20 | Viewed by 4301

Abstract

The dynamic immune response to various diseases and therapies has been considered a promising indicator of disease status and therapeutic effectiveness. For instance, the human peripheral blood mononuclear cell (PBMC), as a major player in the immune system, is an important index to [...] Read more.

The dynamic immune response to various diseases and therapies has been considered a promising indicator of disease status and therapeutic effectiveness. For instance, the human peripheral blood mononuclear cell (PBMC), as a major player in the immune system, is an important index to indicate a patient’s immune function. Therefore, establishing a simple yet sensitive tool that can frequently assess the immune system during the course of disease and treatment is of great importance. This study introduced an integrated system that includes an electrochemical impedance spectroscope (EIS)-based biosensor in a digital microfluidic (DMF) device, to quantify the PBMC abundance with minimally trained hands. Moreover, we exploited the unique droplet manipulation feature of the DMF platform and conducted a dynamic cell capture assay, which enhanced the detection signal by 2.4-fold. This integrated system was able to detect as few as 10⁴ PBMCs per mL, presenting suitable sensitivity to quantify PBMCs. This integrated system is easy-to-operate and sensitive, and therefore holds great potential as a powerful tool to profile immune-mediated therapeutic responses in a timely manner, which can be further evolved as a point-of-care diagnostic device to conduct near-patient tests from blood samples. Full article

(This article belongs to the Special Issue Immunosensors - Trends and Perspective)

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(a) Overview of DMF device with integrated interdigitated electrodes (IDEs). Schematic illustration of the device showing 40 actuation electrodes on the bottom plate and 6 sets of sensing electrodes on the top plate. The sensing electrodes were connected to a multiplexer and an impedance analyzer for the detection; (b) Microscopic image of IDE electrodes deposited on the top plate. (c) Cross-section diagram of the device, with a droplet of cells on the sensing electrodes (not to scale); (d) A photo demonstrating the assembly of an integrated DMF device. DropBot system was used to operate the device; the impedance measurement was conducted by connecting electrical contact pads to a digital impedance analyzer. Full article ">Figure 2
(a) Schematic illustrating the formation of SAM layer, EDC/NHS chemistry and antibody conjugation on the gold electrode surface. (b) FTIR spectrum for amide bonds, C-H alkane chain and N-H stretch. Full article ">Figure 3
(a) The impedance magnitude of IDEs in DMF chip in DI water (non-faradaic regime) and the fitting curve came from Equations (1)–(3) with Cdl = 48 nF, Rsol = 33 kΩ, and Cde = 42 fF. (b) Simplified electrical modeling and (c) equivalent circuit representing the electrode embedded in a DMF platform when a droplet is present. (d) Non-faradic electrochemical impedance spectroscopy (EIS) measured on the IDE in PBS buffer with different concentrations. Full article ">Figure 4
(a) 2D cross-section simulation of electric field distribution of IDEs at (i) 15 μm; (ii) 30 μm; (iii) 50 μm; (b) Electric field intensity at 1 μm below the electrode surface (corresponding to red dotted lines in (a)); (c) Experimental analysis of the impedance measurement performance in terms of the dimension of the IDEs, with error bars denoting standard deviation of n = 3. Full article ">Figure 5
Photos of (a) Droplet incubation in the stationary model; (b) Impedance changes of CD-45 antibody against PBS buffer (no cell present, blank control), IL-6 antibody against PBMCs (negative control), and CD-45 antibody against PBMCs (target). The concentrations of the cell suspensions were 106 per mL. (c) a droplet trajectory in the dynamic incubation mode (1 cycle); (colored fluid was used for better visualization); (d) The relationships between the concentration of PBMCs and the corresponding impedance changes of the integrated EIS sensor in stationary and dynamic modes. The error bars represent the standard deviation of n = 5. Full article ">

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