Biomimetics

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Open AccessEditorial

Bioinspired Catechol-Based Systems: Chemistry and Applications

by Marco D’Ischia and Daniel Ruiz-Molina

Biomimetics 2017, 2(4), 25; https://doi.org/10.3390/biomimetics2040025 - 20 Dec 2017

Cited by 6 | Viewed by 4205

Catechols are widely found in nature taking part in a variety of biological functions, ranging from the aqueous adhesion of marine organisms to the storage of transition metal ions [...]
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(This article belongs to the Special Issue Bioinspired Catechol-Based Systems: Chemistry and Applications)

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Open AccessArticle

EDTA and NTA Effectively Tune the Mineralization of Calcium Phosphate from Bulk Aqueous Solution

by Doreen Hentrich, Klaus Tauer, Montserrat Espanol, Maria-Pau Ginebra and Andreas Taubert

Biomimetics 2017, 2(4), 24; https://doi.org/10.3390/biomimetics2040024 - 13 Dec 2017

Cited by 6 | Viewed by 7250

Abstract

This study describes the effects of nitrilotriacetic acid (NTA) and ethylenediaminotetraacetic acid (EDTA) on the mineralization of calcium phosphate from bulk aqueous solution. Mineralization was performed between pH 6 and 9 and with NTA or EDTA concentrations of 0, 5, 10, and 15 [...] Read more.

This study describes the effects of nitrilotriacetic acid (NTA) and ethylenediaminotetraacetic acid (EDTA) on the mineralization of calcium phosphate from bulk aqueous solution. Mineralization was performed between pH 6 and 9 and with NTA or EDTA concentrations of 0, 5, 10, and 15 mM. X-ray diffraction and infrared spectroscopy show that at low pH, mainly brushite precipitates and at higher pH, mostly hydroxyapatite forms. Both additives alter the morphology of the precipitates. Without additive, brushite precipitates as large plates. With NTA, the morphology changes to an unusual rod-like shape. With EDTA, the edges of the particles are rounded and disk-like particles form. Conductivity and pH measurements suggest that the final products form through several intermediate steps. Full article

(This article belongs to the Special Issue Biomimetic Nanotechnology)

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1206 KiB

Open AccessArticle

Mechanically Reinforced Catechol-Containing Hydrogels with Improved Tissue Gluing Performance

by Jun Feng, Xuan-Anh Ton, Shifang Zhao, Julieta I. Paez and Aránzazu Del Campo

Biomimetics 2017, 2(4), 23; https://doi.org/10.3390/biomimetics2040023 - 13 Nov 2017

Cited by 26 | Viewed by 7077

Abstract

In situ forming hydrogels with catechol groups as tissue reactive functionalities are interesting bioinspired materials for tissue adhesion. Poly(ethylene glycol) (PEG)–catechol tissue glues have been intensively investigated for this purpose. Different cross-linking mechanisms (oxidative or metal complexation) and cross-linking conditions (pH, oxidant concentration, [...] Read more.

In situ forming hydrogels with catechol groups as tissue reactive functionalities are interesting bioinspired materials for tissue adhesion. Poly(ethylene glycol) (PEG)–catechol tissue glues have been intensively investigated for this purpose. Different cross-linking mechanisms (oxidative or metal complexation) and cross-linking conditions (pH, oxidant concentration, etc.) have been studied in order to optimize the curing kinetics and final cross-linking degree of the system. However, reported systems still show limited mechanical stability, as expected from a PEG network, and this fact limits their potential application to load bearing tissues. Here, we describe mechanically reinforced PEG–catechol adhesives showing excellent and tunable cohesive properties and adhesive performance to tissue in the presence of blood. We used collagen/PEG mixtures, eventually filled with hydroxyapatite nanoparticles. The composite hydrogels show far better mechanical performance than the individual components. It is noteworthy that the adhesion strength measured on skin covered with blood was >40 kPa, largely surpassing (>6 fold) the performance of cyanoacrylate, fibrin, and PEG–catechol systems. Moreover, the mechanical and interfacial properties could be easily tuned by slight changes in the composition of the glue to adapt them to the particular properties of the tissue. The reported adhesive compositions can tune and improve cohesive and adhesive properties of PEG–catechol-based tissue glues for load-bearing surgery applications. Full article

(This article belongs to the Special Issue Bioinspired Catechol-Based Systems: Chemistry and Applications)

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Full article ">Figure 1
Adhesion strength of 10 kPa poly(ethylene glycol) O,O′,O′′,O′′′-tetra(acetic acid dopamine) amide (PEG-Dop)/NaIO4-based glues as function of the concentration of individual components in the gluing mixture. (A) Dry and wet test conditions (as compared with commercial tissue glues); (B) Molecular weight of poly(ethylene glycol) (PEG) (15% (w/v) PEG-Dop); (C) PEG-Dop concentration (120 mM NaIO4); (D) Hydroxyapatite (Hap) nanoparticle concentration (15% (w/v) PEG-Dop, 120 mM NaIO4); (E) Collagen (Coll) concentration (15% (w/v) PEG-Dop, 120 mM NaIO4); (F) Oxidant concentration (15% (w/v) PEG-Dop). Failure type: I, interfacial; C, cohesive; C + I, mixture of interfacial and cohesive. * p < 0.05, ** p < 0.01, *** p < 0.001. Full article ">Figure 2
Representative tensile curves of PEG-Dop, PEG-Dop/Coll, composite hydrogel PEG-Dop/HAp, and composite mixture PEG-Dop/Coll/HAp. Concentration of the different components is as follows: 15% (w/v) PEG-Dop, 2.5% (w/v) HAp, 0.1% (w/v) Coll. Full article ">Figure 3
Adhesion strength values of PEG-Dop adhesives (15% (w/v) PEG-Dop, 2.5% (w/v) HAp, 0.1% (w/v) Coll), compared with commercial cyanoacrylate and fibrin glues on dry skin. Failure type: I, interfacial; C, cohesive; T + C, mixture of tissue and cohesive. * p < 0.05, ** p < 0.01, *** p < 0.001. Full article ">Figure 4
Adhesion strength values of PEG-Dop adhesives on “dry” skin, and “wet” skin (either with phosphate-buffered saline (PBS) or with blood) compared with commercial tissue glues. Failure type: I, interfacial; C, cohesive; T + C, mixture of tissue and cohesive. *** p < 0.001. Full article ">Figure 5
Scanning electron microscopy (SEM) images of the bulk structure of (A) PEG-Dop; (B) PEG-Dop/HAp; (C) PEG-Dop/Coll; (D) PEG-Dop/HAp/Coll. Concentration of the different components was: 15% (w/v) PEG-Dop, 2.5% (w/v) HAp, 0.1% (w/v) Coll. In all cases, scale bar: 20 μm. Full article ">

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Open AccessArticle

Copolymerization of a Catechol and a Diamine as a Versatile Polydopamine-Like Platform for Surface Functionalization: The Case of a Hydrophobic Coating

by Salvio Suárez-García, Josep Sedó, Javier Saiz-Poseu and Daniel Ruiz-Molina

Biomimetics 2017, 2(4), 22; https://doi.org/10.3390/biomimetics2040022 - 13 Nov 2017

Cited by 36 | Viewed by 8954

Abstract

The covalent functionalization of surfaces with molecules capable of providing new properties to the treated substrate, such as hydrophobicity or bioactivity, has been attracting a lot of interest in the last decades. For achieving this goal, the generation of a universally functionalizable primer [...] Read more.

The covalent functionalization of surfaces with molecules capable of providing new properties to the treated substrate, such as hydrophobicity or bioactivity, has been attracting a lot of interest in the last decades. For achieving this goal, the generation of a universally functionalizable primer coating in one-pot reaction and under relatively mild conditions is especially attractive due to its potential versatility and ease of application. The aim of the present work is to obtain such a functionalizable coating by a cross-linking reaction between pyrocatechol and hexamethylenediamine (HDMA) under oxidizing conditions. For demonstrating the efficacy of this approach, different substrates (glass, gold, silicon, and fabric) have been coated and later functionalized with two different alkylated species (1-hexadecanamine and stearoyl chloride). The success of their attachment has been demonstrated by evaluating the hydrophobicity conferred to the surface by contact angle measurements. Interestingly, these results, together with its chemical characterization by means of X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR), have proven that the reactivity of the primer coating towards the functionalizing agent can be tuned in function of its generation time. Full article

(This article belongs to the Special Issue Bioinspired Catechol-Based Systems: Chemistry and Applications)

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20829 KiB

Open AccessArticle

Kaxiras’s Porphyrin: DFT Modeling of Redox-Tuned Optical and Electronic Properties in a Theoretically Designed Catechol-Based Bioinspired Platform

by Orlando Crescenzi, Marco D’Ischia and Alessandra Napolitano

Biomimetics 2017, 2(4), 21; https://doi.org/10.3390/biomimetics2040021 - 7 Nov 2017

Cited by 9 | Viewed by 4914

Abstract

A detailed computational investigation of the 5,6-dihydroxyindole (DHI)-based porphyrin-type tetramer first described by Kaxiras as a theoretical structural model for eumelanin biopolymers is reported herein, with a view to predicting the technological potential of this unique bioinspired tetracatechol system. All possible tautomers/conformers, as [...] Read more.

A detailed computational investigation of the 5,6-dihydroxyindole (DHI)-based porphyrin-type tetramer first described by Kaxiras as a theoretical structural model for eumelanin biopolymers is reported herein, with a view to predicting the technological potential of this unique bioinspired tetracatechol system. All possible tautomers/conformers, as well as alternative protonation states, were explored for the species at various degrees of oxidation and all structures were geometry optimized at the density functional theory (DFT) level. Comparison of energy levels for each oxidized species indicated a marked instability of most oxidation states except the six-electron level, and an unexpected resilience to disproportionation of the one-electron oxidation free radical species. Changes in the highest energy occupied molecular orbital (HOMO)–lowest energy unoccupied molecular orbital (LUMO) gaps with oxidation state and tautomerism were determined along with the main electronic transitions: more or less intense absorption in the visible region is predicted for most oxidized species. Data indicated that the peculiar symmetry of the oxygenation pattern pertaining to the four catechol/quinone/quinone methide moieties, in concert with the NH centers, fine-tunes the optical and electronic properties of the porphyrin system. For several oxidation levels, conjugated systems extending over two or more indole units play a major role in determining the preferred tautomeric state: thus, the highest stability of the six-electron oxidation state reflects porphyrin-type aromaticity. These results provide new clues for the design of innovative bioinspired optoelectronic materials. Full article

(This article belongs to the Special Issue Bioinspired Catechol-Based Systems: Chemistry and Applications)

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2169 KiB

Open AccessArticle

Biomimetic Cationic Nanoparticles Based on Silica: Optimizing Bilayer Deposition from Lipid Films

by Rodrigo T. Ribeiro, Victor H. A. Braga and Ana M. Carmona-Ribeiro

Biomimetics 2017, 2(4), 20; https://doi.org/10.3390/biomimetics2040020 - 20 Oct 2017

Cited by 12 | Viewed by 5029

Abstract

The optimization of bilayer coverage on particles is important for a variety of biomedical applications, such as drug, vaccine, and genetic material delivery. This work aims at optimizing the deposition of cationic bilayers on silica over a range of experimental conditions for the [...] Read more.

The optimization of bilayer coverage on particles is important for a variety of biomedical applications, such as drug, vaccine, and genetic material delivery. This work aims at optimizing the deposition of cationic bilayers on silica over a range of experimental conditions for the intervening medium and two different assemblies for the cationic lipid, namely, lipid films or pre-formed lipid bilayer fragments. The lipid adsorption on silica in situ over a range of added lipid concentrations was determined from elemental analysis of carbon, hydrogen, and nitrogen and related to the colloidal stability, sizing, zeta potential, and polydispersity of the silica/lipid nanoparticles. Superior bilayer deposition took place from lipid films, whereas adsorption from pre-formed bilayer fragments yielded limiting adsorption below the levels expected for bilayer adsorption. Full article

(This article belongs to the Special Issue Biomimetic Nanotechnology)

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Full article ">Figure 1
Chemical structures for the cationic lipids and silica micrograph. (a) N-[1-(2,3-dioleoyloxypropyl)-N,N,N-trimethylammonium chloride (DOTAP) chemical structure. (b) Silica particles (AEROSIL OX-50) from transmission electron microscopy (TEM) as provided by the supplier. (c) Dioctadecyldimethylammonium bromide (DODAB) chemical structure. Full article ">Figure 2
Procedure for dispersing silica/cationic lipid from lipid films. The lipid employed was either DOTAP or DODAB. Vortexing was done at an arbitrary temperature of 56 °C, above the mean phase transition temperature of the DODAB or DOTAP bilayer. Full article ">Figure 3
Colloidal stability of silica/cationic lipid dispersions in 1 mM KCl solution over a range of DODAB or DOTAP concentrations at 2 mg/mL silica. DOTAP or DODAB concentrations were 0, 0.05, 0.1, 0.2, 0.3, 0.5, 0.6, and 1.0 mM. BF: Bilayer fragments. Full article ">Figure 4
Size distributions for two different but equivalent dispersions: (a) silica (2 mg/mL); (b) silica/DODAB from DODAB BF at 0.5 mM DODAB; (c) silica/DOTAP dispersions from DOTAP films at 0.5 mM DOTAP; (d) silica/DODAB from DODAB films at 0.5 mM DODAB. Silica and lipid interacted for 24 h in 1 mM KCl solution before taking the supernatants and diluting them by 1:20 for sizing. Dz: Z-average diameter. Full article ">Figure 5
Adsorption isotherms for DOTAP onto silica. (a) Adsorption isotherms for DOTAP onto silica from DOTAP films in pure water. (b) Adsorption isotherms for DOTAP onto silica from DOTAP films in 1 mM KCl. (c) Mean DOTAP adsorption onto silica from DOTAP films in water or in KCl 1 mM aqueous solution. (d) Cross-section of a silica NP covered by a DOTAP cationic bilayer. The dashed line at 0.266 mM DOTAP represents the theoretical concentration for bilayer adsorption. Silica concentration was 2 mg/mL. Each mean adsorption value and the respective mean standard deviation was obtained from at least two different determinations for each element. Full article ">Figure 6
Adsorption isotherms for DODAB onto silica. (a) DODAB adsorption onto silica (2 mg/mL) from DODAB films in pure water. (b) DODAB adsorption on to silica (2 mg/mL) from DODAB BF in pure water. (c) DODAB adsorption onto silica (2 mg/mL) from films in 1 mM KCl water solution. (d) DODAB adsorption onto silica (2 mg/mL) from DODAB BF in 1 mM KCl aqueous solution. The dashed line at 0.288 mM DODAB represents the theoretical concentration for bilayer adsorption. Each mean adsorption value and respective mean standard deviation was obtained from at least two different determinations for each element. Full article ">Figure 7
Adsorption isotherms for DODAB from films or BF onto silica. (a) Mean DODAB adsorption onto silica (2 mg/mL) from DODAB films. (b) Mean DODAB adsorption onto silica (2 mg/mL) from DODAB BF. The dashed line at 0.288 mM DODAB represents the theoretical concentration corresponding to bilayer adsorption. Each mean adsorption value and respective mean standard deviation was obtained from at least two different determinations for each element. Full article ">

3711 KiB

Open AccessArticle

Cell-Adhesive Bioinspired and Catechol-Based Multilayer Freestanding Membranes for Bone Tissue Engineering

by Maria P. Sousa and João F. Mano

Biomimetics 2017, 2(4), 19; https://doi.org/10.3390/biomimetics2040019 - 5 Oct 2017

Cited by 29 | Viewed by 8581

Abstract

Mussels are marine organisms that have been mimicked due to their exceptional adhesive properties to all kind of surfaces, including rocks, under wet conditions. The proteins present on the mussel’s foot contain 3,4-dihydroxy-l-alanine (DOPA), an amino acid from the catechol family that has [...] Read more.

Mussels are marine organisms that have been mimicked due to their exceptional adhesive properties to all kind of surfaces, including rocks, under wet conditions. The proteins present on the mussel’s foot contain 3,4-dihydroxy-l-alanine (DOPA), an amino acid from the catechol family that has been reported by their adhesive character. Therefore, we synthesized a mussel-inspired conjugated polymer, modifying the backbone of hyaluronic acid with dopamine by carbodiimide chemistry. Ultraviolet–visible (UV–Vis) spectroscopy and nuclear magnetic resonance (NMR) techniques confirmed the success of this modification. Different techniques have been reported to produce two-dimensional (2D) or three-dimensional (3D) systems capable to support cells and tissue regeneration; among others, multilayer systems allow the construction of hierarchical structures from nano- to macroscales. In this study, the layer-by-layer (LbL) technique was used to produce freestanding multilayer membranes made uniquely of chitosan and dopamine-modified hyaluronic acid (HA-DN). The electrostatic interactions were found to be the main forces involved in the film construction. The surface morphology, chemistry, and mechanical properties of the freestanding membranes were characterized, confirming the enhancement of the adhesive properties in the presence of HA-DN. The MC3T3-E1 cell line was cultured on the surface of the membranes, demonstrating the potential of these freestanding multilayer systems to be used for bone tissue engineering. Full article

(This article belongs to the Special Issue Bioinspired Catechol-Based Systems: Chemistry and Applications)

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Biomimetics, Volume 2, Issue 4 (December 2017) – 7 articles

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