High strength and bioactivity polyvinyl alcohol/collagen composite hydrogel with tannic acid as cross‐linker

Silver/tannic acid nanoparticles/ poly-L-lysine decorated polyvinyl alcohol-hydrogel as a hybrid wound dressing

Hydrogels containing antimicrobial materials have emerged as attractive platforms for wound treatment in the past decade due to their favorable bio-mimicking properties, excellent modulation of bacterial infection, and ability to minimize bacterial resistance. Herein, a hybrid combination of polyvinyl alcohol (PVA), hyperbranched poly L-lysine (L), tannic acid decorated AgNPs (AgTA NPs), loaded with Allantoin (Alla) is used to fabricate PLAg-Alla hydrogel dressing via the freeze-thaw method without use of any chemical cross-linker. The PLAg-Alla hydrogel possesses a great structure, is biodegradable, and safe, and exhibits high antibacterial potential, all required for efficient wound healing. The incorporation of AgTA and poly L-lysine (L) within the hydrogel contributes to the enhancement of antibacterial ability, as well as effectively promoting the wound healing. This hybrid hydrogel possessed favorable physicochemical features, robust antibacterial properties, and accelerated wound healing in vivo as promising dressing for the clinical application.

Antioxidant Hydrogels: Antioxidant Mechanisms, Design Strategies, and Applications in the Treatment of Oxidative Stress-Related Diseases

Oxidative stress is a biochemical process that disrupts the redox balance due to an excess of oxidized substances within the cell. Oxidative stress is closely associated with a multitude of diseases and health issues, including cancer, diabetes, cardiovascular diseases, neurodegenerative disorders, inflammatory conditions, and aging. Therefore, the developing of antioxidant treatment strategies has emerged as a pivotal area of medical research. Hydrogels have garnered considerable attention due to their exceptional biocompatibility, adjustable physicochemical properties, and capabilities for drug delivery. Numerous antioxidant hydrogels have been developed and proven effective in alleviating oxidative stress. In the pursuit of more effective treatments for oxidative stress-related diseases, there is an urgent need for advanced strategies for the fabrication of multifunctional antioxidant hydrogels. Consequently, the authors' focus will be on hydrogels that possess exceptional reactive oxygen species and reactive nitrogen species scavenging capabilities, and their role in oxidative stress therapy will be evaluated. Herein, the antioxidant mechanisms and the design strategies of antioxidant hydrogels and their applications in oxidative stress-related diseases are discussed systematically in order to provide critical insights for further advancements in the field.

Tough physically crosslinked poly(vinyl alcohol)-based hydrogels loaded with collagen type I to promote bone regeneration in vitro and in vivo

Poly(vinyl alcohol) (PVA) hydrogels exhibit great potential as ideal biomaterials for tissue engineering, owing to their non-toxicity, high water content, and strong biocompatibility. However, limited mechanical strength and low bioactivity have constrained their application in bone tissue engineering. In this study, we have developed a tough PVA-based hydrogel using a facile physical crosslinking method, comprising of PVA, tannic acid (TA), and hydroxyapatite (HA). Systematic experiments were conducted to examine the physicochemical properties of PVA/HA/TA hydrogels, including their compositions, microstructures, and mechanical and rheological properties. The results demonstrated that the PVA/HA/TA hydrogels possessed the porous microstructures and excellent mechanical properties. Furthermore, collagen type I (ColI) was used to further improve the biocompatibility and bioactivity of PVA/HA/TA hydrogels. In vitro experiments revealed that PVA/HA/TA/COL hydrogel could offer a suitable microenvironment for the growth of MC3T3-E1 cells and promote their osteogenic differentiation. Meanwhile, the PVA/HA/TA/COL hydrogel demonstrated the ability to promote bone regeneration and osteointegration in a rat femoral defect model. This study provides a potential strategy for the use of PVA-based hydrogels in bone tissue engineering.

Hyaluronic acid/tannic acid films for wound healing application

In this study, thin films based on hyaluronic acid (HA) with tannic acid (TA) were investigated in three different weight ratios (80HA/20TA, 50HA/50TA, 20HA/80TA) for their application as materials for wound healing. Surface free energy, as well as their roughness, mechanical properties, water vapor permeability rate, and antioxidant activity were determined. Moreover, their compatibility with blood and osteoblast cells was investigated. The irritation effect caused by hyaluronic acid/tannic acid films was also considered with the use of are constructed human epidermis model. The irritation effect for hyaluronic acid/tannic acid films by the in vitro method was also studied. The low surface free energy, surface roughness, and antioxidant activity presented by the obtained films were examined. All the tested compositions of hyaluronic acid/tannic acid films were hemocompatible, but only films based on 50HA/50TA were fully cytocompatible. Regarding the potential implantation, all the films except 80HA/20TA showed appropriate mechanical properties. The specimens did not exert the irritation effect during the studies involving reconstructed human epidermis.

Recent advances in double network hydrogels based on naturally-derived polymers: synthesis, properties, and biological applications

Hydrogels composed of naturally-derived biopolymers have garnered significant research interest due to the bioavailability and biocompatibility of starting materials. However, translating these advantages to practical use is challenged by limitations of mechanical properties and stability of the resulting materials. The development of double network (DN) hydrogels has led to greatly enhanced mechanical properties and shows promise toward broadening the applications of conventional synthetic or natural hydrogels. This review highlights recently developed protein-based and polysaccharide-based DN hydrogels. For each biopolymer, we focus on a subset of DN hydrogels centered around a theme related to synthetic design or applications. Network structures and crosslinking mechanisms that endow enhanced mechanical properties and performance to the materials are discussed. Important applications, including tissue engineering, drug delivery, bioadhesives, wound healing, and wearable sensors, that arise from the inherent properties of the natural polymer or its combination with other materials are also emphasized. Finally, we discuss ongoing challenges to stimulate the discovery of new design principles for the future of DN hydrogels based on naturally-derived polymers for biological applications.

Preparation and characterization of tannin-maltodextrin-polyvinyl alcohol hydrogel based on hydrogen bonding for wound healing

The development of multifunctional and low-cost hydrogel dressings with good mechanical properties, antibacterial activity, and nontoxicity is of great relevance in healthcare. This study aimed to prepare a series of hydrogels consisting of maltodextrin (MD), polyvinyl alcohol (PVA), and tannic acid (TA) through a freeze-thaw cycling technique. Micro-acid hydrogels with different mass ratios (0, 0.25, 0.5, and 1 wt%) were obtained by adjusting the TA content. Among all hydrogels, TA-MP2 hydrogels (with a TA content of 0.5 wt%) showed good physicochemical and mechanical properties. In addition, the biocompatibility of TA-MP2 hydrogels was confirmed by the high cell survival rate of NIH3T3 cells, which was over 90% after 24 h and 48 h of incubation. Additionally, TA-MP2 hydrogels showed multifunctional properties, including antibacterial and antioxidative effects. In vivo experiments showed that TA-MP2 hydrogel dressings significantly accelerated wound healing in a full-layer skin wound model. These findings indicated the potential of TA-MP2 hydrogel dressings in promoting wound healing.

Tannic acid purification from pomegranate peel via tannic acid imprinted particle-embedded cryogel column

Tannic acid (TA) is hydrolysable tannin found in the leaves and bark of many herbaceous and woody plants. Purification of TA is important due to its antibacterial, antihistaminic, antioxidant, antimutagenic and antitussive properties. In this study, 2-hydroxyethyl methacrylate-based TA-imprinted particle embedded cryogel (TA-MIP) was synthesized to purify TA from pomegranate peel. Furthermore, non-imprinted particle embedded cryogel (NIP) was synthesized to determine specific adsorption properties of TA-MIP, and control cryogel was synthesized without embedding procedure. The synthesized cryogel columns were characterized via scanning electron microscopy, Brunauer-Emmett-Teller surface area analysis, fourier-transform infrared spectroscopy, and swelling studies. Particle-embedding procedure resulted in a significantly higher specific surface area of particle-embedded columns (TA-MIP and NIP, 29 m2/g and 25 m2/g, respectively) than the specific surface area of control cryogel (9 m2/g). Adsorption studies were performed from aqueous solutions and maximum TA adsorption was found to be 34.4 mg/g for TA-MIP, 3.9 mg/g for NIP, and 2.8 mg/g for control cryogel. Within the scope of selectivity study, it was demonstrated that the synthesized columns have a high selectivity for TA against gallic acid (GA) and quercetin (QCT). Finally, purification of TA directly from pomegranate peel extract was studied and results were confirmed by HPLC. Furthermore, it has been proven that TA-MIP cryogel columns can be repeatedly used up to ten-times without any remarkable reduction in the TA adsorption amount.

Improved membrane stability of alginate-chitosan microcapsules by crosslinking with tannic acid

OBJECTIVE

The insufficient stability of alginate-chitosan (ALG-CS) microcapsules in biorelevant media limits their applications in the biomedical field. Attempts were made to improve the membrane stability of ALG-CS microcapsules by noncovalent crosslinking with tannic acid.

RESULTS

The membrane stability of ALG-CS microcapsules in culture medium and serum was significantly improved by crosslinking with tannic acid. Moreover, the reason for the significant improvement in membrane stability had been demonstrated to be that the stability of chitosan-tannic acid (CS-TA) polyelectrolyte complexes was less affected by the competitive binding of those weak acid ions such as HCO₃^-. In addition, the optimal conditions for preparing alginate-chitosan-tannic acid (ALG-CS-TA) microcapsules were tannic acid concentration of 0.5% (w/v) and pH = 7.

CONCLUSION

The study provides a novel approach for improving the stability of the ALG-CS microcapsules in biorelevant media to expand their scope of application in the biological field.

Colorimetric pH-responsive and hemostatic hydrogel-based bioadhesives containing functionalized silver nanoparticles

Here we develop and characterize a dual-cross-linked pH-responsive hydrogel based on the carboxyethyl chitosan-oxidized sodium alginate (CAO) containing silver nanoparticles (Ag NPs) functionalized with tannic acid/red cabbage (ATR). This hybrid hydrogel is formed via covalent and non-covalent cross-linking. The adhesive strength measured in contact with cow skin and compression strength is measured more than 3 times higher than that of CAO. Importantly, the incorporation of 1 ​wt% ATR into CAO significantly enhances the compression strength of CAO from 35.1 ​± ​2.1 ​kPa to 97.5 ​± ​2.9 ​kPa. Moreover, the cyclic compression tests confirm significantly higher elastic behavior of CAO after the addition of ATR-functionalized NPs to CAO. The CAO/ATR hydrogel is pH-sensitive and indicated remarkable color changes in different buffer solutions. The CAO/ATR also shows improved hemostatic properties and reduced clotting time compared to the clotting time of blood in contact with CAO hydrogel. In addition, while CAO/ATR is effective in inhibiting the growth of both Gram-positive and Gram-negative bacteria, CAO is only effective in inhibiting the growth of Gram-positive bacteria. Finally, the CAO/ATR hydrogel is cytocompatible with L929 fibroblasts. In summary, the resulting CAO/ATR hydrogel shows promising results in designing and constructing smart wound bioadhesives with high cytocompatibility, antibacterial properties, blood coagulation ability, and fast self-healing properties.

Influence of graphene oxide on rheology, mechanical, dielectric, and triboelectric properties of poly(vinyl alcohol) nanocomposite hydrogels prepared via a facile one step process

The present investigation aims to develop hydrogels with higher mechanical stability for triboelectric applications by adopting a simple method to fabricate a graphene oxide (GO) incorporated poly(vinyl alcohol) (PVA) nanocomposite hydrogel. Instead of the traditional repeated freeze-thaw method, high-shear solution mixing followed by solvent exchange with deionized water was adopted. Morphological observations showed dense and undulated microstructures in the nanocomposite hydrogel with increased GO concentration. Attenuated Total Reflection Fourier Transform Infrared spectroscopy confirmed a higher degree of intermolecular H-bonding between the hydroxyl group of PVA and oxygenated groups of GO, which leads to a robust gel formation. The formation of a robust PVA/GO nanocomposite hydrogel was examined through rheological investigations at room temperature. Nanoindentation analysis estimated a significant increase in hardness and Young's modulus of the nanocomposite hydrogels. Broadband dielectric spectroscopy showed the variation of the dielectric properties of the PVA/GO nanocomposite hydrogels with increased GO concentration. The PVA/GO nanocomposite hydrogels exhibited a maximum output voltage of 3.65 V at 0.075 wt% GO content during finger tapping experiment suggesting the potential for triboelectric applications. The extensive analysis demonstrates the influence of a very low concentration of GO on the variation of the morphology, rheology, mechanical, dielectric, and triboelectric properties of PVA/GO nanocomposite hydrogels.

Nanoarchitectonics of a Skin-Adhesive Hydrogel Based on the Gelatin Resuscitation Fluid Gelatinol®

Hydrogel materials are one of the most versatile representatives of biomaterials. Their widespread use in medical practice is due to their similarity to native biostructures regarding relevant properties. This article discusses the synthesis of hydrogels based on a plasma-substituting Gelatinol^® solution and modified tannin, carried out by direct mixing of the two solutions and brief heating. This approach makes it possible to obtain materials based on precursors that are safe for humans, while having antibacterial activity and high adhesion to human skin. Thanks to the synthesis scheme used, it is possible to obtain hydrogels with a complex shape before use, which is relevant in cases where industrial hydrogels do not fully satisfy the end use regarding their form factor. Using IR spectroscopy and thermal analysis, the distinctive aspects of mesh formation were shown in comparison with the hydrogels based on ordinary gelatin. A number of application properties, such as the physical and mechanical characteristics, permeability to oxygen/moisture, and antibacterial effect, were also considered. The sorption parameters of the material were characterized in a set of physiological buffers (pH 2-9) using Fick's first law and a pseudo-second order equation. The adhesive shear strength was determined in a model system. The synthesized hydrogels showed potential for the further development of materials based on plasma-substituting solutions.

Lignin nanoparticle reinforced multifunctional polyvinyl alcohol/polyurethane composite hydrogel with excellent mechanical, UV-blocking, rheological and thermal properties

In this study, we innovatively synthesized a multifunctional PVA/PU-LNP composite hydrogel with integrated distinguished UV-blocking, mechanical strength, dynamic viscoelasticity and thermal properties by introducing lignin nanoparticle (LNP) into polyvinyl alcohol (PVA) and polyurethane (PU) mixed matrix through freeze-thaw cycle. The rigid porous network structure was established by hydrogen bond interactions among the well-distributed LNP and PVA/PU molecular chains, which endowed excellent mechanical strength, viscoelasticity, thermal stability and flexibility with PVA/PU-LNP composite hydrogel. The elongation at break and tensile strength of PVA/PU-LNP composite hydrogel were markedly improved from 227.3 % and 247.1 KPa to 460.1 % and 950.4 KPa with the LNP loading of 2 % based on PVA weight, respectively. Meanwhile, PVA/PU-2%LNP hydrogel exhibited prominent compressive resistance and pleasing shape recovery capability. Moreover, the blending of LNP at a low dosage (0.5 %) based on PVA weight effectively shielded 99.34 % of UV light and penetrated 42.27 % of visible light, indicating that PVA/PU-LNP composite hydrogel demonstrated outstanding anti-UV performance. In addition, the incorporation of LNP caused a remarkable decline in the pore size of PVA/PU-LNP composite hydrogel (4.39 ± 0.46 μm to 1.54 ± 0.22 μm), which slightly reduced water uptake capacity of composite hydrogel. Therefore, this work provided a new approach to constructing a multifunctional composite hydrogel.

Strategical development of chrome-free tanning agent by integrating layered double hydroxide with starch derivatives

The development of sustainable and eco-friendly leather industry requires green tanning agents because of unbounded chromium (easily converted into hazardous Cr-VI) in chrome tanned leather. In this study, a chrome-free tanning agent (OS-LDHs) was established by integrating layered double hydroxide (magnesium aluminum zirconium hydrotalcite, LDHs) with starch derivatives. A series of oxidized starch (OS) were prepared as masking agents for LDHs tanning process. Among them, the weight-average molecular weight (Mw) of 1685 g/mol could be reached, which will promise the well-distribution of OS. The SEM and EDS analysis confirmed the uniform penetration of OS-LDHs, avoiding accumulation on the surface of crust leather. Notably, leather tanned by OS-LDHs achieved shrinkage temperature of 66.7 °C, porosity of 75.51 % and tear strength of 66.7 N/mm. Not only the hydrogen bond but also the coordination between NH₂, COOH in collagen and OS-2-LDHs improved the thermal stability of leather without destroying the collagen triple helix.

Highly stretchable, self-healing, and degradable ionic conductive cellulose hydrogel for human motion monitoring

Self-healing biomass-based conductive hydrogels are applied as flexible strain sensors for wearable devices and human movement monitoring. Cellulose is the most abundant biomass-based materials and exhibits excellent toughness, dispersion and degradability. In this paper, nanocellulose crystals (NCCs) prepared from sisal, used as reinforcing fillers were coated with tannic acid (TA) to prepare inexpensive bio-nanocomposite hydrogels that also included polyvinyl alcohol, okra polysaccharide (OP), and borax. These hydrogels exhibit excellent self-healing and mechanical properties with the maximum elongation, toughness, and self-healing efficiency (9 min) of 1426.2 %, 264.4 kJ/m³, and 62.1 %, respectively. A fabricated hydrogel strain sensor was successfully used to detect and monitor various human movements such as wrist bending, elbow bending, and slight changes in facial expression. In addition, this sensor possessed excellent durability and good working stability after repeated circulation. The nanocomposite hydrogel synthesized in this work utilized natural polysaccharide to manufacture flexible functional materials with good application prospects in the field of flexible sensors.

A Polyvinyl Alcohol-Tannic Acid Gel with Exceptional Mechanical Properties and Ultraviolet Resistance

Design and preparation of gels with excellent mechanical properties has garnered wide interest at present. In this paper, preparation of polyvinyl alcohol (PVA)-tannic acid (TA) gels with exceptional properties is documented. The crystallization zone and hydrogen bonding acted as physical crosslinkages fabricated by a combination of freeze-thaw treatment and a tannic acid compound. The effect of tannic acid on mechanical properties of prepared PVA-TA gels was investigated and analyzed. When the mass fraction of PVA was 20.0 wt% and soaking time was 12 h in tannic acid aqueous solution, tensile strength and the elongation at break of PVA-TA gel reached 5.97 MPa and 1450%, respectively. This PVA-TA gel was far superior to a pure 20.0 wt% PVA hydrogel treated only with the freeze-thaw process, as well as most previously reported PVA-TA gels. The toughness of a PVA-TA gel is about 14 times that of a pure PVA gel. In addition, transparent PVA-TA gels can effectively prevent ultraviolet-light-induced degradation. This study provides a novel strategy and reference for design and preparation of high-performance gels that are promising for practical application.

Drug-Loaded and Anisotropic Wood-Derived Hydrogel Periosteum with Super Antibacterial, Anti-Inflammatory, and Osteogenic Activities

Current artificial periostea mainly focus on osteogenic activity but overlook structural and mechanical anisotropy, as well as the importance of antibacterial and anti-inflammatory properties. Here, inspired by the anisotropic structure of wood, the delignified wood (named white wood, WW) with a porous and highly oriented cellulose fiber skeleton was obtained, which was further filled with polyvinyl alcohol (PVA) hydrogel loaded with curcumin (Cur) and phytic acid (PA). The prepared wood-derived hydrogel composite membranes can not only exhibit an obvious anisotropic structure and good mechanical properties but also sustainably release loaded drugs to obtain long-term biological activities. Creatively, PA can effectively improve the bioavailability of Cur; more importantly, Cur and PA play an obvious synergistic effect in antibacterial, anti-inflammatory, and osteogenic activities. Compared with the wood-derived hydrogel composite membranes without drug loading, as well as loaded with Cur or PA only, these loaded with Cur and PA are significantly more conducive to inhibiting the growth of bacteria and inflammatory response and facilitating the adhesion, proliferation, and osteogenic differentiation of bone marrow mesenchymal stem cells. This kind of anisotropic wood-derived hydrogel composite membrane with fantastic antibacterial, anti-inflammatory, and osteogenic activities is expected to be ideal artificial periostea.

Poly(vinyl alcohol) nanofibrous membranes via green electrospinning and tannin coating for selective removal of Pb(II) ion

The conventional adsorbent fabrication methods involve complicated processes and may cause secondary contaminations. Therefore, an effective eco-friendly method is required for the fabrication of heavy metal adsorbents using inexpensive and eco-friendly materials without secondary pollution during their process. In this study, nanofibrous membranes (NFMs) were fabricated via green electrospinning of poly(vinyl alcohol) (PVA), a hydrophilic polymer, and their water resistance was improved through simple heat treatment without using additional additives. Then, nanofibrous heavy metal adsorbents were prepared by dip-coating the NFMs in an aqueous solution of tannic acid (TA), a natural polyphenol. First, the adsorption/desorption behavior of TA on PVA NFMs during the TA coating process was investigated. In addition, the effects of TA coating on the mechanical properties and heavy metal adsorption characteristics of the PVA NFMs were analyzed. The TA coating significantly increased the mechanical strength, heat resistance, and heavy metal (Pb(II)) adsorption capacity of the PVA NFM. The Pb²⁺ adsorption amount of TA-coated PVA NFMs exhibited about 5-7 times higher than those of other heavy metal ions, indicating excellent selectivity for Pb²⁺. In addition, the TA-coated PVA NFMs retained >70% of its initial adsorption capacity even after four cycles of adsorption/desorption, indicating its reusability.

Novel high strength PVA/soy protein isolate composite hydrogels and their properties

High strength polyvinyl alcohol (PVA)/soy protein isolate (SPI) composite hydrogels (EPSG) were constructed by the introduction of PVA into SPI through the crosslinking with epichlorohydrin (ECH) and a freezing-thawing process. The EPSG hydrogels were characterized by scanning electron microscopy, FTIR, X-ray diffraction and compressive test. The results revealed that chemical crosslinking interactions occurred for SPI and PVA during the fabrication process. The composite hydrogels exhibited a homogenous porous structure, indicating certain miscibility between PVA and SPI. The introduction of PVA increased the compressive strength of SPI hydrogels greatly, which could reach as high as 5.38 MPa with the water content ratio of 89.5%. Moreover, the water uptake ratio of completely dried SPI hydrogel (namely xerogel) decreased gradually from 327.4% to 148.1% with the incorporation of PVA, showing a better potential as implants. The cytocompatibility and hemocompatibility of the EPSG hydrogels were evaluated by a series of in vitro experiments. The results showed that the EPSG hydrogels had no cytotoxicity (cell viability values were above 86.7%), good biocompatibility and hemocompatibility, showing potential applications as a direct blood contact material in the field of tissue engineering.

Tannic acid: a versatile polyphenol for design of biomedical hydrogels

Tannic acid (TA), a natural polyphenol, is a hydrolysable amphiphilic tannin derivative of gallic acid with several galloyl groups in its structure. Tannic acid interacts with various organic, inorganic, hydrophilic, and hydrophobic materials such as proteins and polysaccharides via hydrogen bonding, electrostatic, coordinative bonding, and hydrophobic interactions. Tannic acid has been studied for various biomedical applications as a natural crosslinker with anti-inflammatory, antibacterial, and anticancer activities. In this review, we focus on TA-based hydrogels for biomaterials engineering to help biomaterials scientists and engineers better realize TA's potential in the design and fabrication of novel hydrogel biomaterials. The interactions of TA with various natural or synthetic compounds are deliberated, discussing parameters that affect TA-material interactions thus providing a fundamental set of criteria for utilizing TA in hydrogels for tissue healing and regeneration. The review also discusses the merits and demerits of using TA in developing hydrogels either through direct incorporation in the hydrogel formulation or indirectly via immersing the final product in a TA solution. In general, TA is a natural bioactive molecule with diverse potential for engineering biomedical hydrogels.

Development of sodium alginate/glycerol/tannic acid coated cotton as antimicrobial system

Present study aims at developing antimicrobial cotton gauze by dip coating of sodium alginate (SA), glycerol (Gly) and tannic acid (TA) blend. SA blends were prepared with varying concentration of glycerol in the range of 10-40 %. Blended films were fabricated and characterized by Fourier transform-infrared (FTIR) spectroscopy, X-ray diffraction (XRD), tensile studies, and contact angle analysis. The mechanical behavior of films indicated significant decrease in the tensile strength and modulus with the increase in the glycerol content due to the plasticization effect. The hydrophilicity of the blend films increased with increase in the glycerol content. TA was added to the blend as an antimicrobial agent. These blends were coated on the cotton gauze by dip coating method and their characterizations were carried out by the scanning electron microscopy (SEM) which revealed a smooth coating of SA:Gly:TA blend on cotton gauze. Antimicrobial analysis of TA coated gauzes was carried out which showed >95 % viable colony reduction against E. coli and S. aureus. Cytocompatibility studies indicated excellent cell-compatible activity. These results implicated that such coated gauzes are promising candidate that hold the great potential to be utilized as infection-resistant material in the health care sector.

The Influence of Oxidant on Gelatin-Tannin Hydrogel Properties and Structure for Potential Biomedical Application

Nowadays, there is a widespread usage of sodium periodate as an oxidant for synthesizing gelatin-tannin hydrogels. The impact of iodine compounds could have a harmful effect on human health. The study focuses on the proposal of alternative oxidizing systems for tannin oxidation. Gelatin-tannin hydrogels were obtained based on the usage of H2O2/DMSO/KMnO4/KIO4 oxidants and characterized with sorption, thermal (TGA, DTG, DSC), mechanical, FTIR and other methods. The sorption experiments were carried out in a phosphate buffer (pH = 5.8/7.4/9) and distilled water and were investigated with Fick's law and pseudosecond order equation. The pH dependence of materials in acid media indicates the possibility of further usage as stimuli-responsive systems for drug delivery. Thermal transitions demonstrate the variation of structure with melting (306 ÷ 319 °C) and glass transition temperatures (261 ÷ 301 °C). The activation energy of water evaporation was calculated by isoconversional methods (Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa) ranging from 4 ÷ 18 to 14 ÷ 38 kJ/mole and model-fitting (Coats-Redfern, Kennedy-Clark) methods at 24.7 ÷ 45.3 kJ/mole, indicating the smooth growth of values with extent of conversion. The network parameters of the hydrogels were established by modified Flory-Rehner and rubber elasticity theories, which demonstrated differences in values (5.96 ÷ 21.27·10-3 mol/cm3), suggesting the limitations of theories. The sorption capacity, tensile strength and permeability for water/oxygen indicate that these materials may find their application in field of biomaterials.

Tunable and tough porous chitosan/β-cyclodextrin/tannic acid biocomposite membrane with mechanic, antioxidant, and antimicrobial properties

Herein, tannic acid (TA)-reinforced chitosan (CHS)/β-cyclodextrin (β-CD) biocomposite membranes were prepared by TA solution incubating treatment. The functional groups, crystal structure, and morphological characterizations of the prepared biocomposite membranes were investigated using various methods. The biocomposite membranes were investigated in terms of their wettability, porosity, swelling degree, and water uptake. In vitro antioxidant investigation was carried out through DPPH assay. Moreover, the prepared biocomposite membranes were evaluated for their antimicrobial ability against three different microbial species. The introduction of TA effectively improved the swelling behavior, mechanical strength, and porosity of the biocomposite membranes. TA increased the tensile strength from 0.7 ± 0.2 MPa to a maximum of 2.2 ± 0.6 MPa and elongation at break from 26.9 ± 0.7% to a maximum of 36.7 ± 3.5%. The biocomposite membranes showed an initial burst release of TA (~40%) within 6 h, followed by a gradual release of 100% by 18 h. Furthermore, the introduction of TA into the biocomposite membranes further improved the antimicrobial activities against both bacteria and yeast, as well as the in vitro antioxidant potential. As a consequence, the prepared biocomposite membranes could potentially be used as scaffold in broaden biomedical fields due to their adaptable structure, porosity, greatly antioxidant, and antimicrobial activity.