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Background/Objectives: Although the use of radiation-sensitizing agents has been shown to enhance the effect of radiation on tumor cells, the blood–brain barrier (BBB) impedes these agents from reaching brain tumor sites when provided systemically. Localized methods of sensitizer delivery, utilizing hydrogels, have the potential to bypass the blood–brain barrier. This study examined the ability of photochemical internalization (PCI) of hydrogel-released bleomycin to enhance the growth-inhibiting effects of radiation on multi-cell glioma spheroids in vitro. Methods: Loaded fibrin hydrogel layers were created by combining thrombin, fibrinogen, and bleomycin (BLM). Supernatants from these layers were collected, combined with photosensitizer, and added to F98 glioma spheroid cultures. Following light (PCI) and radiation treatment, at increasing dosages, spheroid growth was monitored for 14 days. Results: PCI of released BLM significantly reduced the radiation dose required to achieve equivalent efficacy compared to radiation or BLM + RT alone. Both immediate and delayed RT delivery post-BLM-PCI resulted in similar degrees of growth inhibition. Conclusions: Non-degraded BLM was released from the fibrin hydrogel. PCI of BLM synergistically increased the growth-inhibiting effects of radiation treatment compared to radiation and BLM, as well as radiation acting as a single treatment. Full article

(This article belongs to the Special Issue Novel Targeted Therapies in Brain Tumors)

16 pages, 3822 KiB

Open AccessArticle

Detecting Hypoxia Through the Non-Invasive and Simultaneous Monitoring of Sweat Lactate and Tissue Oxygenation

by Cindy Cheng, Sayan Ganguly, Pei Li and Xiaowu Tang

Biosensors 2024, 14(12), 584; https://doi.org/10.3390/bios14120584 (registering DOI) - 30 Nov 2024

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Abstract

Hypoxia, characterized by inadequate tissue oxygenation, may result in tissue damage and organ failure if not addressed. Current detection approaches frequently prove insufficient, depending on symptoms and rudimentary metrics such as tissue oxygenation, which fail to comprehensively identify the onset of hypoxia. The European Pressure Ulcer Advisory Panel (EPUAP) has recognized sweat lactate as a possible marker for the early identification of decubitus ulcers, nevertheless, neither sweat lactate nor oxygenation independently provides an appropriate diagnosis of hypoxia. We have fabricated a wearable device that non-invasively and concurrently monitors sweat lactate and tissue oxygenation to fill this gap. The apparatus comprises three essential components: (i) a hydrogel-based colorimetric lactate biosensor, (ii) a near-infrared (NIR) sensor for assessing tissue oxygenation, and (iii) an integrated form factor for enhanced wearability. The lactate sensor alters its hue upon interaction with lactate in sweat, whereas the NIR sensor monitors tissue oxygenation levels in real-time. The device underwent testing on phantom exhibiting tissue-mimicking characteristics and on human sweat post aerobic and anaerobic activities. Moreover, the device was demonstrated to be capable of real-time “on-body” simultaneous monitoring of sweat lactate spikes and tissue oxygenation (StO₂) drops, which showed strong correlation during a hypoxia protocol. This innovative technology has a wide range of potential applications, such as post-operative care, sepsis detection, and athletic performance monitoring, and may provide economical healthcare solutions in resource-limited regions. Full article

(This article belongs to the Special Issue Biosensors for Monitoring and Diagnostics)

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Schematic illustration of (a) the lactate-sensing hydrogel composition and (b) the colorimetric sensing mechanism. Oxidation of lactate, catalyzed by LOX, generates H2O2 as a byproduct; TMB reacts with H2O2, catalyzed by HRP, results in a color change. (c) Optical absorption peaks of TMB (350 nm) and TMBox (one-electron oxidation, 660 and 960 nm; two-electron oxidation, 450 nm). Full article ">Figure 2
(a) Images of gels in a multi-well plate in response to various lactate concentrations at various time points. (b) Representative optical absorption spectra of gels in response to lactate. Full article ">Figure 3
(a) An exploded view of the device prototype. Pictures of an assembled wearable device, (b) without, and (c) with the gel. Optical pathways from LEDs to PDs (d) without and (e) with the lactate sensing hydrogel on tissue. Left: simulation in tissue; right: bottom view of the wearable device. Full article ">Figure 4
(a) Picture of the device placed on top of an optical phantom with optical properties mimicking those of human tissue (StO2 = 68%). (b) Normalized absorption of the lactate sensing hydrogels, extracted from the optical readout, in response to various lactate solutions (0, 10, 40, 80 mM) in phosphate buffer (pH 6.0) respectively. (c,d) Stable StO2 and BVI reading regardless of lactate concentration. Full article ">Figure 5
(a) Picture of the test setup showing the device worn on the researcher’s left thigh while on a stational bike, with the laptop running data collection software. (b) Normalized absorption vs. time response curves for the aerobic and anaerobic conditions. Inset-left up: appearance of gel before and after the test; inset-right down: lactate detection calibration curve. Full article ">Figure 6
(a) Picture of a student researcher sitting in a sauna tent to stimulate sweating while a pressure cuff was used to create temporary hypoxia in the forearm. (b) A zoomed-in view of the pressure cuff worn on the upper arm and the wearable device on the forearm. (c–e) Simultaneous monitoring of sweat lactate production (top panel), tissue oxygenation level (middle panel), and BVI (bottom panel). Full article ">

23 pages, 8866 KiB

Open AccessArticle

New Carrageenan/2-Dimethyl Aminoethyl Methacrylate/Gelatin/ZnO Nanocomposite as a Localized Drug Delivery System with Synergistic Biomedical Applications

by Abeer A. Ageeli and Sahera F. Mohamed

Processes 2024, 12(12), 2702; https://doi.org/10.3390/pr12122702 (registering DOI) - 30 Nov 2024

Viewed by 387

Abstract

In recent years, the development of multifunctional hydrogels has gained significant attention due to their potential in various biomedical applications, including antimicrobial, antioxidant, and anticancer therapies. By integrating biocompatible polymers and nanoparticles, these hydrogels can achieve enhanced activity and targeted therapeutic effects. In this study, carrageenan/2-dimethyl aminoethyl methacrylate/gelatin (CAR/DEMA/Gelt) composite hydrogel was synthesized using microwave radiation specifically for its efficiency in enhancing cross-linking and promoting uniform nanoparticle dispersion within the matrix. Zinc oxide (ZnO) nanoparticles were incorporated into the hydrogel to form the (CAR/DEMA/Gelt/ZnO) nanocomposite. The hydrogels were characterized using FT-IR, FE-SEM, XRD, TGA, and EDX, confirming successful cross-linking and structural integrity. The nanocomposite hydrogel exhibited more enhanced antimicrobial activity than the composite hydrogel against Gram-positive Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtilis), with inhibition zones of 15 mm and 16 mm, respectively, while in case of the Gram-negative bacteria, Klebsiella pneumoniae (K. pneumoniae) and Escherichia coli (E. coli), the inhibition zones were 29 mm and 19 mm, respectively. In addition to the unicellular fungi, Candida albicans (C. albicans), the inhibition zone was 19 mm. Moreover, the nanocomposite showed anti-inflammatory activity comparable to those of Indomethacin and antioxidant activity, with an impressive IC₅₀ value of 33.3 ± 0.05 µg/mL. In vitro cytotoxicity assays revealed significant anticancer activity. Against the MCF-7 breast cancer cell line, the CAR/DEMA/Gelt/ZnO nanocomposite showed 72.5 ± 0.02% cell viability, which decreased to 30.8 ± 0.01% after loading doxorubicin (DOX). Similarly, against the HepG2 liver cancer cell line, the free nanocomposite displayed 59.9 ± 0.006% cell viability, which depleted to 29.9 ± 0.005% when DOX was uploaded. This CAR/DEMA/Gelt/ZnO nanocomposite hydrogel demonstrates strong potential as a multifunctional platform for targeted biomedical applications, particularly in cancer therapy. Full article

(This article belongs to the Special Issue Advances in Nanomaterials: Synthesis, Characterization and Applications)

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19 pages, 4159 KiB

Open AccessArticle

Microwave-Assisted Production of Defibrillated Lignocelluloses from Blackcurrant Pomace via Citric Acid and Acid-Free Conditions

by Natthamon Inthalaeng, Ryan E. Barker, Tom I. J. Dugmore and Avtar S. Matharu

Molecules 2024, 29(23), 5665; https://doi.org/10.3390/molecules29235665 (registering DOI) - 29 Nov 2024

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Abstract

Blackcurrant pomace (BCP) is an example of an annual, high-volume, under-utilized renewable resource with potential to generate chemicals, materials and bioenergy within the context of a zero-waste biorefinery. Herein, the microwave-assisted isolation, characterization and potential application of defibrillated lignocelluloses from depectinated blackcurrant pomace are reported. Depectination was achieved using citric acid (0.2–0.8 M, 80 °C, 2 h, conventional heating) and compared with acid-free hydrothermal microwave-assisted processing (1500 W, 100–160 °C, 30 min). The resultant depectinated residues were subjected to microwave-assisted hydrothermal defibrillation to afford two classes of materials: namely, (i) hydrothermal acid-free microwave-assisted (1500 W, 160 °C, 30 min; DFC-M1-M4), and (ii) hydrothermal citric acid microwave-assisted (1500 W, 160 °C, 30 min; DFC-C1–C4). Thermogravimetric analysis (TGA) revealed that the thermal stability with respect to native BCP (T_d = 330 °C) was higher for DFC-M1-M4 (T_d = 345–348 °C) and lower for DFC-C1–C4 (322–325 °C). Both classes of material showed good propensity to hold water but failed to form stable hydrogels (5–7.5 wt% in water) unless they underwent bleaching which removed residual lignin and hemicellulosic matter, as evidenced by ¹³C solid-state NMR spectroscopy. The hydrogels made from bleached DFC-C1–C4 (7.5 wt%) and bleached DFC-M1-M4 (5 wt%) exhibited rheological viscoelastic, shear thinning, and time-dependent behaviour, which highlights the potential opportunity afforded by microwave-assisted defibrillation of BCP for food applications. Full article

14 pages, 3383 KiB

Open AccessArticle

Fabrication and Characterization of Phyllanthus Emblica Extract-Polyvinyl Alcohol/Carboxymethyl Cellulose Sodium Antioxidant Hydrogel and Its Application in Wound Healing

by Shanqin Huang, Shanglun Li, Guoyan Li, Chenyu Wang, Xiaohan Guo, Jing Zhang, Jing Liu, Ying Xu and Yanchun Wang

Pharmaceutics 2024, 16(12), 1531; https://doi.org/10.3390/pharmaceutics16121531 - 29 Nov 2024

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Abstract

Background: Phyllanthus emblica is a medicinal and edible plant from the Euphorbiaceae family, notable for its rich content of polyphenols and flavonoids, which provide significant antioxidant properties. To exploit the full antioxidant potential of Phyllanthus emblica, this study developed a hydrogel system incorporating polyvinyl alcohol (PVA) and carboxymethyl cellulose sodium (CMC-Na), integrated with Phyllanthus emblica extract, for the purpose of wound healing. Methods: The extraction process of active ingredients of Phyllanthus emblica was optimized and assessed the antioxidant composition and activity of the extract. A series of hydrogel performance evaluations were performed on the Phyllanthus emblica extract-loaded PVA/CMC-Na hydrogel (AEPE composite hydrogel). Additionally, the wound healing efficacy was evaluated through cell culture experiments and wound healing assays using BALB/C mice. Results: The findings indicated that the extraction of Phyllanthus emblica with 95% ethanol yielded an extract rich in polyphenols, primarily gallic acid and ellagic acid, demonstrating high free radical scavenging capacity and robust antioxidant activity. The hydrogel matrix containing 12% PVA and 1% CMC-Na exhibited excellent physicochemical properties. The optimized AEPE composite hydrogel enabled sustained drug release over a 24 h period, exhibited low cytotoxicity and promoted cell migration. In a mouse dorsal wound healing model, the AEPE composite hydrogel showed pronounced anti-inflammatory and antioxidation effects, enhanced collagen deposition, and ultimately accelerated wound healing. Conclusions: The AEPE composite hydrogel demonstrated strong antioxidant characteristics and significant wound healing potential. Thus, this study could broaden the application prospects of Phyllanthus emblica in wound healing. Full article

(This article belongs to the Section Physical Pharmacy and Formulation)

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18 pages, 5815 KiB

Open AccessArticle

Aluminum-Free Borosilicate Glass Functionalized Hydrogels for Enhanced Dental Tissue Regeneration

by Nina Attik, Inès Basri, Jérôme Sohier, Rémy Gauthier, Cyril Villat and Christelle Goutaudier

Materials 2024, 17(23), 5862; https://doi.org/10.3390/ma17235862 - 29 Nov 2024

Viewed by 233

Abstract

Hydrogels are promising scaffolds for tissue regeneration, and borosilicate glass particles have demonstrated potential in enhancing the biological behaviour of dental pulp cells. However, the specific morphological characteristics of dental lesions and the diverse requirements of dental tissues require biocompatible, bioactive, and shapeable scaffolds. This study aimed to evaluate the in vitro biological behaviour of human gingival fibroblasts (HGFs) in contact with an experimental aluminum-free borosilicate glass-functionalized hydrogel. Two types of experimental borosilicate glass particles were utilized, with Biodentine^® particles serving as a reference material. The hydrogel, based on poly(L-lysine) dendrimers (DGL) with or without borosilicate particles, was analyzed using micro-computed tomography (µCT) and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX). Cytocompatibility was assessed using Live/Dead™ staining, and cell colonization was evaluated via confocal imaging. Additionally, Alizarin red staining was performed to assess mineralization potential after 7 and 14 days. Results indicated that the incorporation of borosilicate particles did not alter hydrogel porosity, while EDX confirmed particle presence on the hydrogel surfaces. Furthermore, the borosilicate-functionalized hydrogels significantly enhanced cell proliferation, colonization, and the content of calcium deposits. These findings highlight the potential of these hydrogels for future clinical applications in dental tissue regeneration, pending further development. Full article

(This article belongs to the Special Issue Bioactive Glass-Based Materials for Soft and Hard Tissue Regeneration: A New Future for Dental and Biomedical Applications)

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50 pages, 19208 KiB

Open AccessReview

Nanotechnology in Drug Delivery: Anatomy and Molecular Insight into the Self-Assembly of Peptide-Based Hydrogels

by Adelaide R. Mashweu and Vladimir A. Azov

Molecules 2024, 29(23), 5654; https://doi.org/10.3390/molecules29235654 - 29 Nov 2024

Viewed by 358

Abstract

The bioavailability, release, and stability of pharmaceuticals under physicochemical conditions is the major cause of drug candidates failing during their clinical trials. Therefore, extensive efforts have been invested in the development of novel drug delivery systems that are able to transport drugs to a desired site and improve bioavailability. Hydrogels, and peptide hydrogels in particular, have been extensively investigated due to their excellent biocompatibility and biodegradability properties. However, peptide hydrogels often have weak mechanical strength, which limits their therapeutic efficacy. Therefore, a number of methods for improving their rheological properties have been established. This review will cover the broad area of drug delivery, focusing on the recent developments in this research field. We will discuss the variety of different types of nanocarrier drug delivery systems and then, more specifically, the significance and perspectives of peptide-based hydrogels. In particular, the interplay of intermolecular forces that govern the self-assembly of peptide hydrogels, progress made in understanding the distinct morphologies of hydrogels, and applications of non-canonical amino acids in hydrogel design will be discussed in more detail. Full article

(This article belongs to the Section Materials Chemistry)

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17 pages, 4747 KiB

Open AccessFeature PaperArticle

Physicochemical Properties, Drug Release and In Situ Depot-Forming Behaviors of Alginate Hydrogel Containing Poorly Water-Soluble Aripiprazole

by Hy D. Nguyen, Munsik Jang, Hai V. Ngo, Myung-Chul Gil, Gang Jin, Jing-Hao Cui, Qing-Ri Cao and Beom-Jin Lee

Gels 2024, 10(12), 781; https://doi.org/10.3390/gels10120781 (registering DOI) - 29 Nov 2024

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Abstract

The objective of this study was to investigate the physicochemical properties, drug release and in situ depot-forming behavior of alginate hydrogel containing poorly water-soluble aripiprazole (ARP) for achieving free-flowing injectability, clinically accessible gelation time and sustained drug release. The balanced ratio of pyridoxal phosphate (PLP) and glucono-delta-lactone (GDL) was crucial to modulate gelation time of the alginate solution in the presence of calcium carbonate. Our results demonstrated that the sol state alginate hydrogel before gelation was free-flowing, stable and readily injectable using a small 23 G needle. In addition, the ratio (w/w) of PLP and GDL altered the gelation time, which was longer as the PLP content increased but shorter as the GDL content increased. The alginate hydrogel with a ratio of PLP to GDL of 15:9 had the optimal physicochemical properties in terms of a clinically acceptable gelation time (9.1 min), in situ-depot formation with muscle-mimicking stiffness (3.55 kPa) and sustained release over a two-week period. The alginate hydrogel, which is tunable by varying the ratio of PLP and GDL, could provide a controllable pharmaceutical preparation to meet the need for long-acting performance of antipsychotic drugs like ARP. Full article

(This article belongs to the Special Issue Engineering Advanced Hydrogels for Biomedical Applications (2nd Edition))

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17 pages, 7803 KiB

Open AccessArticle

Effect of Adding Gold Nanoparticles on the Anti-Candidal Activity and Release Profile of Itraconazole from Hydrogels

by Radosław Balwierz, Paweł Biernat, Dawid Bursy, Mariia Shanaida, Katarzyna Kasperkiewicz, Agata Jasińska-Balwierz and Wioletta Ochędzan-Siodłak

Appl. Sci. 2024, 14(23), 11125; https://doi.org/10.3390/app142311125 - 29 Nov 2024

Viewed by 552

Abstract

Gold nanoparticles have been identified as a promising avenue for the development of drug carriers, particularly in the context of antimicrobial drug delivery, where limited solubility represents a significant challenge. The ability of gold nanoparticles to penetrate biofilms and disrupt fungal cell membranes makes them an effective tool to support antifungal therapy, especially against resistant strains. Gold nanoparticles also demonstrate synergistic effects with chemotherapeutics and can influence the release profile of the active substances. This study aimed to develop a topical hydrogel drug formulation containing itraconazole (ITZ), with the addition of gold nanoparticles, to enhance its therapeutic properties. Due to ITZ’s poor water solubility, three types of the gold nanoparticles (AuNPs) of different sizes were synthesized and subsequently coated with itraconazole. The resulting formulations were incorporated into carbopol gels and their ability to diffuse through semipermeable membranes was assessed. The findings demonstrated that the combination of gold nanoparticles and itraconazole elevated the diffusion coefficient to twice the level observed in gels without nanoparticles. Furthermore, the combined effect of gold nanoparticles and itraconazole against a reference Candida albicans strain was investigated. The combination of gold nanoparticles and itraconazole demonstrated a growth-inhibitory effect on this strain, indicating that this formulation could potentially be employed in the treatment of fungal infections. The study confirms that hydrogels with itraconazole and gold nanoparticles can be obtained, offering enhanced drug diffusion. Full article

(This article belongs to the Special Issue Nanomaterials in Medical Diagnosis and Therapy)

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The FTIR spectra of the studied materials. Full article ">Figure 2
Dependence of the diffusion rate on the time element for the obtained hydrogel formulations. Full article ">Figure 3
Amount of active substance released as a function of time element for all gel formulations. Full article ">Figure 4
Candida albicans growth kinetics tested for selected hydrogels formulations. Full article ">

16 pages, 2157 KiB

Open AccessArticle

A Fluorescent Perspective on Water Structuring: ACDAN in Salt Solutions and Hydrogels

by Giuseppe De Luca, Vittorio Ferrara, Bruno Pignataro, Valeria Vetri and Giuseppe Sancataldo

Biophysica 2024, 4(4), 619-633; https://doi.org/10.3390/biophysica4040041 (registering DOI) - 28 Nov 2024

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Abstract

The interactions and structural organization of water molecules play a crucial role in a wide range of physical, chemical, and biological processes. The ability of water to form hydrogen bonds (H-bonds) underpins its unique properties and enables it to respond dynamically to various environmental factors. These interactions at the molecular level may affect vital processes like protein folding, enzyme activity, and cellular organization. The presence of solutes and spatial constraints can alter the H-bonding network of water, and these effects are ubiquitous in the biological environment. In this study, we analyzed the fluorescence of 2-acetyl-6-(dimethylamino)naphthalene (ACDAN) fluorescence emission in water solutions containing kosmotropic and chaotropic salts and in agar hydrogels. Recently, this dye has proven invaluable in studying water network structure and dynamics, as its fluorescence signal changes based on the local dielectric environment, revealing variations in the dipolar relaxation of water. Our results show that ACDAN spectral response correlates with the degree of water ordering, providing important insights into solute–water interactions and water dynamics in free and confined environments. Full article

(This article belongs to the Special Issue Biomedical Optics 2.0)

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NIR absorbance of the water solution of kosmotropic salts of (a) sodium dihydrogen phosphate (Na2HPO4) and (b) sodium sulfate (Na2SO4) at 1 M, 2 M, and 3 M. The spectrum of pure water is reported for comparison. NIR spectra have been normalized by the water mass concentration. ACDAN fluorescence emission spectra in (c) Na2HPO4 and (d) Na2SO4 water solutions (λexc = 380 nm, detection range = 370–650 nm). Fluorescence spectra have been normalized to the maximum intensity. Full article ">Figure 2
NIR absorbance of the water solution of chaotropic salts of (a) sodium chloride (NaCl) and (b) sodium perchlorate (NaClO4) at 1 M, 2 M, and 3 M. The spectrum of pure water is reported for comparison. NIR spectra have been normalized by the water mass concentration. ACDAN fluorescence emission spectra in (c) NaCl and (d) NaClO4 water solutions (λexc = 380 nm, detection range = 370–650 nm). Fluorescence spectra have been normalized to the maximum intensity. Full article ">Figure 3
(a) ACDAN fluorescence emission spectra (λexc = 380 nm, detection range = 370–650 nm) measured in agar hydrogels as a function of agar concentration ranging from 0.01% to 1.0% (wt/wt). ACDAN fluorescence emission spectrum in water is reported as well. Fluorescence spectra have been normalized to the maximum intensity. (b) GP analysis of the ACDAN fluorescence emission band, measured at 475 nm and 550 nm. The empty green circle is the GP value calculated from the water spectrum. Full article ">Figure 4
Time evolution of hydrogel formation was monitored on a sample consisting of a 0.5% wt/wt agar solution for 250 min. (a) Rayleigh scattering of the sample measured at 650 nm during 20 °C thermal gelification. (b) ACDAN fluorescence emission spectra as a function of time (λexc = 380 nm, detection range = 370–650 nm). Fluorescence spectra have been normalized to the maximum intensity. (c) GP analysis of the ACDAN fluorescence emission band, calculated at 475 nm and 550 nm as a function of time. (d) Differential spectra of the 1450 nm NIR absorption band. (e) Maximum of the differential NIR spectra as a function of time. Full article ">

18 pages, 980 KiB

Open AccessArticle

3D Bioprintable Self-Healing Hyaluronic Acid Hydrogel with Cysteamine Grafting for Tissue Engineering

by Kasula Nagaraja, Amitava Bhattacharyya, Minsik Jung, Dajeong Kim, Mst Rita Khatun and Insup Noh

Gels 2024, 10(12), 780; https://doi.org/10.3390/gels10120780 (registering DOI) - 28 Nov 2024

Viewed by 236

Abstract

The abundance of hyaluronic acid (HA) in human tissues attracts its thorough research in tissue regenerating scaffolds and 3D bioprintable hydrogel preparation. Though methacrylation of HA can lead to photo-crosslinkable hydrogels, the catalyst has toxicity concerns, and the hydrogel is not suitable for creating stable complex 3D structures using extrusion 3D bioprinting. In this study, a dual crosslinking on methacrylated HA is introduced, using cysteamine-grafted HA and varying concentrations of 2-hydroxy ethyl acrylate. The resultant hydrogel is suitable for extrusion 3D printing (or bioprinting), mechanically robust, self-standing, stable in phosphate-buffered saline at 37 °C for more than 42 days, has high water absorption capacity with a low swelling ratio (1.5), and exhibits self-healing and adhesive properties. Complex 3D structures like ears and pyramid shapes with more than 2 cm of height are 3D printed using the optimized composition. All the synthesized hydrogels have shown nontoxicity and cell-supportiveness. Loading of cells, tetracycline, and bovine serum albumin into the hydrogel led to better bioink properties such as cell attachment, growth, and proliferation for osteoblast cells. The test results suggest that this hydrogel is biocompatible and has potential for 3D bioprinting of self-standing structures in bioink form in tissue engineering and regenerative medicine. Full article

(This article belongs to the Special Issue Recent Trends in Gels for 3D Printing)

16 pages, 3008 KiB

Open AccessArticle

Adsorption of Cr(VI) Using Organoclay/Alginate Hydrogel Beads and Their Application to Tannery Effluent

by Mayra X. Muñoz-Martinez, Iván F. Macías-Quiroga and Nancy R. Sanabria-González

Gels 2024, 10(12), 779; https://doi.org/10.3390/gels10120779 - 28 Nov 2024

Viewed by 329

Abstract

The tanning industry is among the most environmentally harmful activities globally due to the pollution of lakes and rivers from its effluents. Hexavalent chromium, a metal in tannery effluents, has adverse effects on human health and ecosystems, requiring the development of removal techniques. This study assessed the efficacy of organobentonite/alginate hydrogel beads in removing Cr(VI) from a fixed-bed adsorption column system. The synthesized organobentonite (OBent) was encapsulated in alginate, utilizing calcium chloride as a crosslinking agent to generate hydrogel beads. The effects of the volumetric flow rate, bed height, and initial Cr(VI) concentration on a synthetic sample were analyzed in the experiments in fixed-bed columns. The fractal-like modified Thomas model showed a good fit to the experimental data for the asymmetric breakthrough curves, confirmed by the high R² correlation coefficients and low χ² values. The application of organoclay/alginate hydrogel beads was confirmed with a wastewater sample from an artisanal tannery industry in Belén (Nariño, Colombia), in which a Cr(VI) removal greater than 99.81% was achieved. Organobentonite/alginate hydrogels offer the additional advantage of being composed of a biodegradable polymer (sodium alginate) and a natural material (bentonite-type clay), resulting in promising adsorbents for the removal of Cr(VI) from aqueous solutions in both synthetic and real water samples. Full article

(This article belongs to the Special Issue Alginate-Based Gels: Preparation, Characterization and Application (2nd Edition))

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29 pages, 6429 KiB

Open AccessArticle

Investigation of Silver- and Plant Extract-Infused Polymer Systems: Antioxidant Properties and Kinetic Release

by Magdalena Bańkosz and Bożena Tyliszczak

Int. J. Mol. Sci. 2024, 25(23), 12816; https://doi.org/10.3390/ijms252312816 - 28 Nov 2024

Viewed by 218

Abstract

This study evaluated the impact of silver particles, suspended in Arnica montana flower extract, on the physicochemical characteristics and release dynamics of antioxidant compounds in PVP (polyvinylpyrrolidone)-based hydrogel systems. The hydrogels were synthesized via photopolymerization with fixed amounts of crosslinker (PEGDA) and photoinitiator, while the concentration of the silver-infused extract was systematically varied. Key properties, including the density, porosity, surface roughness, swelling capacity, and water vapor transmission rate (WVTR), were quantitatively analyzed. The results demonstrated that increasing the silver content reduced the hydrogel density from 0.6669 g/cm³ to 0.2963 g/cm³ and increased the porosity from 4% to 11.04%. The surface roughness parameters (Ra) rose from 8.42 µm to 16.33 µm, while the WVTR increased significantly from 65.169 g/m²·h to 93.772 g/m²·h. These structural changes directly influenced the release kinetics of antioxidant compounds, with kinetic modeling revealing silver-dependent variations in the evaluated release mechanisms. This innovative approach of integrating silver particles and plant-derived antioxidants into hydrogels highlights a novel pathway for tailoring material properties. The observed enhanced porosity and moisture regulation underscore the hydrogels’ potential for biomedical applications, particularly in wound care, where controlled moisture and antioxidant delivery are critical. These findings provide new insights into how silver particles modulate hydrogel structures and functionalities. Full article

(This article belongs to the Special Issue Structural and Functional Polymer Materials in Biomedicine)

15 pages, 4134 KiB

Open AccessArticle

Nanostructured Hydrogels of Carboxylated Cellulose Nanocrystals Crosslinked by Calcium Ions

by Alexander S. Ospennikov, Yuri M. Chesnokov, Andrey V. Shibaev, Boris V. Lokshin and Olga E. Philippova

Gels 2024, 10(12), 777; https://doi.org/10.3390/gels10120777 (registering DOI) - 28 Nov 2024

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Abstract

Bio-based eco-friendly cellulose nanocrystals (CNCs) gain an increasing interest for diverse applications. We report the results of an investigation of hydrogels spontaneously formed by the self-assembly of carboxylated CNCs in the presence of CaCl₂ using several complementary techniques: rheometry, isothermal titration calorimetry, FTIR-spectroscopy, cryo-electron microscopy, cryo-electron tomography, and polarized optical microscopy. Increasing CaCl₂ concentration was shown to induce a strong increase in the storage modulus of CNC hydrogels accompanied by the growth of CNC aggregates included in the network. Comparison of the rheological data at the same ionic strength provided by NaCl and CaCl₂ shows much higher dynamic moduli in the presence of CaCl₂, which implies that calcium cations not only screen the repulsion between similarly charged nanocrystals favoring their self-assembly, but also crosslink the polyanionic nanocrystals. Crosslinking is endothermic and driven by increasing entropy, which is most likely due to the release of water molecules surrounding the interacting COO⁻ and Ca²⁺ ions. The hydrogels can be easily destroyed by increasing the shear rate because of the alignment of rodlike nanocrystals along the direction of flow and then quickly recover up to 90% of their viscosity in 15 s, when the shear rate is decreased. Full article

(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (3rd Edition))

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17 pages, 3866 KiB

Open AccessArticle

Preparation and Rheological Evaluation of Thiol–Maleimide/Thiol–Thiol Double Self-Crosslinking Hyaluronic Acid-Based Hydrogels as Dermal Fillers for Aesthetic Medicine

by Chia-Wei Chu, Wei-Jie Cheng, Bang-Yu Wen, Yu-Kai Liang, Ming-Thau Sheu, Ling-Chun Chen and Hong-Liang Lin

Gels 2024, 10(12), 776; https://doi.org/10.3390/gels10120776 - 28 Nov 2024

Viewed by 229

Abstract

This study presents the development of thiol–maleimide/thiol–thiol double self-crosslinking hyaluronic acid-based (dscHA) hydrogels for use as dermal fillers. Hyaluronic acid with varying degrees of maleimide substitution (10%, 20%, and 30%) was synthesized and characterized, and dscHA hydrogels were fabricated using two molecular weights of four-arm polyethylene glycol (PEG10K/20K)–thiol as crosslinkers. The six resulting dscHA hydrogels demonstrated solid-like behavior with distinct physical and rheological properties. SEM analysis revealed a decrease in porosity with higher crosslinker MW and maleimide substitution. The swelling ratios of the six hydrogels reached equilibrium at approximately 1 h and ranged from 20% to 35%, indicating relatively low swelling. Degradation rates decreased with increasing maleimide substitution, while crosslinker MW had little effect. Higher maleimide substitution also required greater injection force. Elastic modulus (G′) in the linear viscoelastic region increased with maleimide substitution and crosslinker MW, indicating enhanced firmness. All hydrogels displayed similar creep-recovery behavior, showing instantaneous deformation under constant stress. Alternate-step strain tests indicated that all six dscHA hydrogels could maintain elasticity, allowing them to integrate with the surrounding tissue via viscous deformation caused by the stress exerted by changes in facial expression. Ultimately, the connection between the clinical performance of the obtained dscHA hydrogels used as dermal filler and their physicochemical and rheological properties was discussed to aid clinicians in the selection of the most appropriate hydrogel for facial rejuvenation. While these findings are promising, further studies are required to assess irritation, toxicity, and in vivo degradation before clinical use. Overall, it was concluded that all six dscHA hydrogels show promise as dermal fillers for various facial regions. Full article

(This article belongs to the Special Issue Recent Research on Medical Hydrogels)

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Full article ">Figure 1
1H NMR (A) and FTIR spectra (B) of HA and HA-Mal with three different degrees of substitution of maleimide on HA (HM10, HM20, and HM30). Full article ">Figure 2
Reaction scheme illustrating the formation of dscHA hydrogels. Full article ">Figure 3
SEM images of six dscHA hydrogels (HM10-4SH10K (A), HM20-4SH10K (B), HM30-4SH10K (C), HM10-4SH20K (D), HM20-4SH20K (E), and HM30-4SH20K (F). (Scale bar: 500 µm). Full article ">Figure 4
The swelling ratio profiles (A) and degradation profiles (B) for HAs with various levels of maleimide substitution and thiol-containing crosslinkers with two different MWs (designated as HM10-4SH10K, HM10-4SH20K, HM20-4SH10K, HM20-4SH20K, HM30-4SH10K, and HM30-4SH20K, respectively). Full article ">Figure 5
Injection force through a 26 G needle measured for six dscHA hydrogels (HM10-4SH10K, HM10-4SH20K, HM20-4SH10K, HM20-4SH20K, HM30-4SH10K, and HM30-4SH20K). Full article ">Figure 6
Rheological evaluation of dscHA hydrogels. Amplitude sweep (A) and frequency sweep (B) of the six dscHA hydrogels, showing the linear viscoelastic (LVE) region and gel behavior. Tan δ values (C) of the six dscHA hydrogels, indicating whether the behavior is elastic-dominant or viscous-dominant. Full article ">Figure 7
Creep-recovery experiments (constant stress) were performed with an applied shear stress of 5 Pa for 10 min followed by 20 min of recovery (A), and alternate-step strain tests with five repetitions of shear-stress application and relaxation (B) were performed to study the deformation and recovery of the hydrogel network. Full article ">

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