Preparation and Characterization of Collagen–Chitosan–Chondroitin Sulfate Composite Membranes

Collagen (Col)–chitosan (Chi) membrane was modified by a hot dehydrogenation cross-linking method. Carbodiimide was added for further crossing modification. Chondroitin sulfate (CS) was added so that Col–Chi sulfate composite membranes were prepared. The structure of the composite membranes was characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, and its mechanical properties, degradation, and cytotoxicity were characterized. The composite membrane was applied to a full-thickness skin injury in animal experiments performed in rabbits. Strong interactions and good compatibility among Col, Chi, and CS in the composite membrane were present. The good mechanical properties, biocompatibility, digestion resistance, and wound healing promotion of the composite membrane make it a potential wound dressing or skin scaffold for tissue engineering.     

Studies of chitosan: II. Preparation and characterization of chitosan/poly(vinyl alcohol)/gelatin ternary blend films

Chitosan/poly(vinyl alcohol)/gelatin (CS/PVA/GA) ternary blend films were prepared by solution blending method in this study. The thermal properties of the CS/PVA/GA ternary blend films were examined by differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The melting point of the CS/PVA/GA ternary blend film was increased when the amount of GA in the blend film was increased based upon the DSC thermal analysis. Results of X-ray diffraction (XRD) analyses indicated that the intensity of diffraction peak at 19 degrees of PVA became lower and broader with increasing the amount of GA in the CS/PVA/GA ternary blend film. Although CS, PVA, and GA are hydrophilic biodegradable polymers, the results of water contact angle measurements are still as high as 83 degrees, 68 degrees, and 66 degrees, respectively. A minimum water contact angle (56 degrees) was observed when the ternary blend film contains 50 wt.% GA (i.e. GA5). This behavior is primarily due to the reorientation of polar functional groups toward to the top surface of CS/PVA/GA ternary blend films.     

Chitosan-functionalized silk fibroin 3D scaffold for keratocyte culture

The goal of this study was to evaluate the potential suitability of an artificial membrane composed of silk fibroin (SF) functionalized by different ratios of chitosan (CS) as a substrate for the stroma of the cornea. Keratocytes were cultured on translucent membranes made of SF and CS with different ratios. The biophysical properties of the silk fibroin and chitosan (SF/CS) membrane were examined. The SF/CS showed tensile strengths that increased as the CS concentration increased, but the physical and mechanical properties of chitosan-functionalized silk fibroin scaffolds weakened significantly compared with those of native corneas. The resulting cell scaffolds were evaluated using western blot in addition to light and electron microscopy. The cell attachment and proliferation on the scaffold were similar to those on a plastic plate. Keratocytes cultured in serum on SF/CS exhibited stellate morphology along with a marked increase in the expression of keratocan compared with identical cultures on tissue culture plastics. The biocompatibility was tested by transplanting the acellular membrane into rabbit corneal stromal pockets. There was no inflammatory complication detected at any time point on the macroscopic level. Taken together, these results indicate that SF/CS holds promise as a substrate for corneal reconstruction.     

Facile preparation of well-defined near-monodisperse chitosan/sodium alginate polyelectrolyte complex nanoparticles (CS/SAL NPs) via ionotropic gelification: A suitable technique for drug delivery systems

Polymeric nanoparticles have emerged as a promising approach for drug delivery systems. We prepared chitosan (CS)/sodium alginate (SAL) polyelectrolyte complex nanoparticles (CS/SAL NPs) via a simple and mild ionic gelation method by adding a CS solution to a SAL solution, and investigated the effects of molecular weight of the added CS, and the SAL:CS mass ratio on the formation of the polyelectrolyte complex nanoparticles. The well-defined CS/SAL NPs with near-monodisperse particle size of about 160 nm exhibited a pH stable structure, and pH responsive properties with a negatively or positively charged surface. The so-called “electrostatic sponge” structure of the polyelectrolyte complex nanoparticles enhanced their drug-loading capacity towards the differently charged model drug molecules, and favored controlled release. We also found that the drug-loading capacity was influenced by the nature of the drugs and the drug-loading media, while drug release was affected by the solubility of the drugs in the drug-releasing media. The biocompatibility and biodegradability of the polyelectrolytes in the polyelectrolyte complex nanoparticles were maintained by ionic interactions. These results indicate that CS/SAL NPs can represent a useful technique for pH-responsive drug delivery systems.     

Synthesis and characterization of chitosan/ZnO nanoparticle composite membranes

Novel chitosan/ZnO nanoparticle (CS/nano-ZnO) composite membranes were prepared via the method of sol-cast transformation and studied by UV-vis absorption spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray fluorescence spectrometry (EDX). The characterization revealed that ZnO nanoparticles dispersed homogeneously within the chitosan matrix. The mechanical and antibacterial properties of the product were investigated. The results showed that the ZnO content had an effect on the mechanical properties of CS/nano-ZnO composite membranes, and that the antibacterial activities of CS membranes for Bacillus subtilis, Escherichia coli, and Staphylococcus aureus were enhanced by the incorporation of ZnO. Further, CS/nano-ZnO composite membranes with 6-10 wt % ZnO exhibited high antibacterial activities.     

Comparison of protein fouling on heat-treated poly(vinyl alcohol), poly(ether sulfone) and regenerated cellulose membranes using diffuse reflectance infrared Fourier transform spectroscopy

Poly(vinyl alcohol) (PVA) membranes for ultrafiltration were fabricated by heat-treatment to separate macromolecules from microsolutes. PVA is a hydrophilic polymer with good mechanical properties because of its semicrystalline structure. The membranes were heat-treated at 100 degrees C for 1 h to increase their crystallinity and thereby their mechanical strength. The mechanical strength of the membranes was evaluated using a dynamic mechanical analyzer by measuring their compressive and tensile moduli. Membrane selectivities and protein fouling of heat-treated PVA membranes were compared to the commercial poly(ether sulfone) (PeS) and regenerated cellulose membranes. Myoglobin from horse skeletal muscle was used as a model protein, and L-tryptophan was used as a model microsolute. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to identify protein fouling on the surfaces of these membranes under flow and nonflow conditions. It was found from the selectivity and DRIFTS studies that PVA membranes were more resistant to fouling than regenerated cellulose and PeS membranes.     

The molecular simulation of the miscibility,mechanical properties and physical cross-linking behavior of the poly(vinyl alcohol)/poly(acrylic acid) composited membranes

The miscibility and mechanical properties of poly vinyl alcohol (PVA) and poly acrylic acid (PAA)-composited membranes were studied with molecular simulation. The Flory–Huggins parameters (δ) were calculated to prove the good miscibility of PVA and PAA. The radial distribution functions of hydroxyl and carboxyl atoms and the average number of H-bonds were observed to indicate the degree of physical cross-linking between PVA and PAA. The influences of intermolecular physical cross-linking on the glass transition temperature and mechanical properties were estimated. The results revealed that the PVA/PAA membrane with a composition of 2:3 has the best plastic properties, which exhibits a good application value. All of the simulated results showed good agreement with the experimental data. It indicates that the method presented in this work has a promising application prospect.     

Wet chemical synthesis of chitosan hydrogel–hydroxyapatite composite membranes for tissue engineering applications

Chitosan, a deacetylated derivative of chitin is a commonly studied biomaterial for tissue-engineering applications due to its biocompatibility, biodegradability, low toxicity, antibacterial activity, wound healing ability and haemostatic properties. However, chitosan has poor mechanical strength due to which its applications in orthopedics are limited. Hydroxyapatite (HAp) is a natural inorganic component of bone and teeth and has mechanical strength and osteoconductive property. In this work, HAp was deposited on the surface of chitosan hydrogel membranes by a wet chemical synthesis method by alternatively soaking the membranes in CaCl₂ (pH 7.4) and Na₂HPO₄ solutions for different time intervals. These chitosan hydrogel–HAp membranes were characterized using SEM, AFM, EDS, FT-IR and XRD analyses. MTT assay was done to evaluate the biocompatibility of these membranes using MG-63 osteosarcoma cells. The biocompatibility studies suggest that chitosan hydrogel–HAp composite membranes can be useful for tissue-engineering applications.     

Effect of crosslinking in chitosan/aloe vera-based membranes for biomedical applications

The positive interaction between polysaccharides with active phytochemicals found in medicinal plants may represent a strategy to create active wound dressing materials useful for skin repair. In the present work, blended membranes composed of chitosan (Cht) and aloe vera gel were prepared through the solvent casting, and were crosslinked with genipin to improve their properties. Topography, swelling, wettability, mechanical properties and in vitro cellular response of the membranes were investigated. With the incorporation of aloe vera gel into chitosan solution, the developed chitosan/aloe-based membranes displayed increased roughness and wettability; while the genipin crosslinking promoted the formation of stiffer membranes in comparison to those of the non-modified membranes. Moreover, in vitro cell culture studies evidenced that the L929 cells have high cell viability, confirmed by MTS test and calcein-AM staining. The findings suggested that both blend compositions and crosslinking affected the physico-chemical properties and cellular behavior of the developed membranes.     

Preparation and biological properties of a novel composite scaffold of nano-hydroxyapatite/chitosan/carboxymethyl cellulose for bone tissue engineering

In this study, we report the physico-chemical and biological properties of a novel biodegradable composite scaffold made of nano-hydroxyapatite and natural derived polymers of chitosan and carboxymethyl cellulose, namely, n-HA/CS/CMC, which was prepared by freeze-drying method. The physico-chemical properties of n-HA/CS/CMC scaffold were tested by infrared absorption spectra (IR), transmission electron microscope(TEM), scanning electron microscope(SEM), universal material testing machine and phosphate buffer solution (PBS) soaking experiment. Besides, the biological properties were evaluated by MG63 cells and Mesenchymal stem cells (MSCs) culture experiment in vitro and a short period implantation study in vivo. The results show that the composite scaffold is mainly formed through the ionic crossing-linking of the two polyions between CS and CMC, and n-HA is incorporated into the polyelectrolyte matrix of CS-CMC without agglomeration, which endows the scaffold with good physico-chemical properties such as highly interconnected porous structure, high compressive strength and good structural stability and degradation. More important, the results of cells attached, proliferated on the scaffold indicate that the scaffold is non-toxic and has good cell biocompatibility, and the results of implantation experiment in vivo further confirm that the scaffold has good tissue biocompatibility. All the above results suggest that the novel degradable n-HA/CS/CMC composite scaffold has a great potential to be used as bone tissue engineering material.     

The Novelty in Fabrication of Poly Vinyl Alcohol/κ-Carrageenan Hydrogel with <Emphasis Type="Italic">Lactobacillus bulgaricus</Emphasis> Extract as Anti-inflammatory Wound Dressing Agent

Material barrier properties to microbes are an important issue in many pharmaceutical applications like wound dressings. A wide range of biomaterials has been used to manage the chronic inflamed wounds. Eight hydrogel membranes of poly vinyl alcohol (PVA) with κ-carrageenan (KC) and Lactobacillus bulgaricus extract (LAB) have been prepared by using freeze–thawing technique. To evaluate the membranes efficiency as wound dressing agents, various tests have been done like gel fraction, swelling behavior, mechanical properties, etc. The antibacterial activities of the prepared membranes were tested against the antibiotic-resistant bacterial isolates. In addition, the safety usage of the prepared hydrogel was checked on human dermal fibroblast cells. The anti-inflammatory properties of the prepared hydrogel on LPS-PBMC cell inflammatory model were quantified using enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-qPCR). The analysis data of TGA, SEM, gel fraction, and swelling behavior showed changes in properties of prepared PVA\KC\LAB hydrogel membrane than pure PVA hydrogel membrane. The antibacterial activities of the prepared membranes augmented in LAB extract-prepared membranes. Out of the eight used hydrogel membranes, the PVAKC4 hydrogel membrane is the safest one on fibroblast cellular proliferation with a maximum proliferation percentage 97.3%. Also, all the used hydrogel membrane showed abilities to reduce the concentration of IL-2 and IL-8 compared with both negative and positive control. In addition, almost all the prepared hydrogel membrane showed variable abilities to downregulate the expression of TNF-α gene with superior effect of hydrogel membrane KC1. PVA/KC/LAB extract hydrogel membrane may be a promising material for wound dressing application and could accelerate the healing process of the chronic wound because of its antimicrobial and anti-inflammatory properties.     

Synthesis of antibacterial PVA/CM-chitosan blend hydrogels with electron beam irradiation

A series of excellent hydrogels were prepared from poly(vinyl alcohol) (PVA) and carboxymethylated chitosan (CM-chitosan) with electron beam irradiation (EB) at room temperature. Electron spectroscopy analysis of the blend hydrogels revealed that good miscibility was sustained between CM-chitosan and PVA. The properties of the prepared hydrogels, such as the mechanical properties, gel fraction and swelling behavior were investigated. The mechanical properties and equilibrium degree of swelling improved obviously after adding CM-chitosan into PVA hydrogels. The gel fraction determined gravimetrically showed that a part of CM-chitosan was immobilized onto PVA hydrogel. The further analyses of FTIR and DSC spectra of the prepared gels after extracting sol manifested that there was a grafting interaction between PVA and CM-chitosan molecules under irradiation. The antibacterial activity of the hydrogels against Escherichia coli was also measured via optical density method. The blend hydrogels exhibited satisfying antibacterial activity against E. coli, even when the CM-chitosan concentration was only 3 wt%.     

Preparation and characterization of chitosan-polyvinyl alcohol blend hydrogels for the controlled release of nano-insulin

Chitosan (CS)-polyvinyl alcohol (PVA) blend hydrogels were prepared using glutaraldehyde as the cross-linking agent. The obtained hydrogels, which have the advantages of both PVA and CS, can be used as a material for the transdermal drug delivery (TDD) of insulin. The nano-insulin-loaded hydrogels were prepared under the following conditions: 1.2 g of polyethylene glycol, 1.5 g of CS, 1.2 g of PVA, 1.2 mL of 1% glutaraldehyde solution, 16 mL of water, and 40 mg of nano-insulin with 12 min of mixing time and 3 min of cross-linking time. The nano-insulin-loaded hydrogels were characterized using scanning electron microscopy, energy dispersive spectrometry, Fourier-transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction, and its mechanical properties were analyzed. The results show that all molecules in the hydrogel have good compatibility and they formed a honeycomb-like structure. The hydrogel also showed good mechanical and thermal properties. The in vitro drug release of the hydrogel showed that the nano-insulin accorded with Fick's first law of diffusion and it has a high permeation rate (4.421 μg/(cm² h)). These results suggest that the nano-insulin-loaded hydrogels are a promising non-invasive TDD system for diabetes chemotherapy.     

Chitosan scaffolds containing silicon dioxide and zirconia nano particles for bone tissue engineering

A scaffold harboring the desired features such as biodegradation, biocompatibility, porous structure could serve as template for bone tissue engineering. In the present study, chitosan (CS), nano-scaled silicon dioxide (Si) and zirconia (Zr) were combined by freeze drying technique to fabricate a bio-composite scaffold. The bio-composite scaffold (CS/Si/Zr) was characterized by SEM, XRD and FT-IR studies. The scaffold possessed a porous nature with pore dimensions suitable for cell infiltration and colonization. The presence of zirconia in the CS/Si/Zr scaffold decreased swelling and increased biodegradation, protein adsorption and bio-mineralization properties. The CS/Si/Zr scaffold was also found to be non-toxic to rat osteoprogenitor cells. Thus, we suggest that CS/Si/Zr bio-composite scaffold is a potential candidate to be used for bone tissue engineering.     

Molecular dynamics study of the influence of solvents on the structure and mechanical properties of poly(vinyl alcohol) gels

Molecular dynamics (MD) simulations were employed to study the influence of solvents on the structure and mechanical properties of physically crosslinked poly(vinyl alcohol) (PVA) gels. Firstly, three kinds of PVA precursor gels were made by adding water, dimethyl sulfoxide (DMSO) and a mixture of DMSO and water (4:1 by weight), respectively. The solvents in the precursor gels were then exchanged with water to obtain three kinds of PVA hydrogels. Solvent in the precursor gel with a mixture of DMSO and water was also exchanged with ethanol and DMSO, respectively. It was found that the tensile strength and failure strain of the PVA hydrogel prepared from precursor gel with a mixture of DMSO and water was the highest, and the polymer network was more homogeneous than the other two PVA hydrogels. The polymer network of PVA gel with ethanol or with DMSO was more heterogenous than with water, and the tensile strength and failure strain were much lower. The torsional activity of polymer chains of PVA gel with ethanol was much stronger than PVA gel with water and DMSO.     

Modified natural halloysite/potato starch composite films

Halloysite/potato starch composites were prepared by adding modified natural halloysite nanotubes into potato starch matrices to reenforce the mechanical properties of potato starch films. The halloysite/potato starch films were characterized by X-ray diffraction, scanning electron microscope and infrared spectrometry. Meanwhile, the mechanical properties and transparency of the films were studied. The results show that the modified halloysite nanotubes can be well distributed in the starch matrix and thus the tensile strength of the films was clearly enhanced. The flexibility of the films could be improved through adding glycerol although at the cost of reducing tensile strength. But incorporation of PVA could further improve the tensile strength of the halloysite/potato starch films.     

Biomimetic Hydrophobic Surfaces with Low or High Adhesion Based on Poly(vinyl alcohol) and SiO2 Nanoparticles

Superhydrophobic surfaces are often found in nature,such as plant leaves and insect wings.Inspired by superhydrophobic phenomenon of the rose petals and the lotus leaves,biomimetic hydrophobic surfaces with high or low adhesion were prepared with a facile drop-coating approach in this paper.Poly(vinyl alcohol) (PVA) was used as adhesive and SiO2 nanoparticles were used to fabricate surface micro-structure.Stearic acid or dodecafluoroheptyl-propyl-trimethoxysilane (DFTMS) were used as low surface energy materials to modify the prepared PVA/SiO2 coating surfaces.The effects of size of SiO2 nanoparticles,concentration of SiO2 nanoparticle suspensions and the modifications on the wettability of the surface were investigated.The morphology of the PVA/SiO2 coating surfaces was observed by using scanning electron microscope.Water contact angle of the obtained superhydrophilic surface could reach to 3°.Stearic acid modified PVA/SiO2 coating surfaces showed hydrophobicity with high adhesion.By mixing the SiO2 nanoparticles with sizes of 40 nm and 200 nm and modifying with DFTMS,water contact angle of the obtained coating surface could be up to 155° and slide angle was only 5°.This work provides a facile and useful method to control surface wettability through changing the roughness and chemical composition of a surface.     

Preparation and characterization of novel beta-chitin-hydroxyapatite composite membranes for tissue engineering applications

Beta-chitin is a biopolymer principally found in shells of squid pen. It has the properties of biodegradability, biocompatibility, chemical inertness, wound healing, antibacterial and anti-inflammatory activities. Hydroxyapatite (HAp) is a natural inorganic component of bone and teeth and has osteoconductive property. In this work, beta-chitin-HAp composite membranes were prepared by alternate soaking of beta-chitin membranes in CaCl2 (pH 7.4) and Na2HPO4 solutions for 2 h in each solution. After 1, 3 and 5 cycles of immersion, beta-chitin membranes were characterized using the SEM, FT-IR, EDS and XRD analyses. The results showed the presence of apatite layer on surface of beta-chitin membranes, and the amounts of size and deposition of apatite layers were increased with increasing number of immersion cycles. Human mesenchymal stem cells (hMSCs) were used for evaluation of the biocompatibility of pristine as well as composite membranes for tissue engineering applications. The presence of apatite layers on the surface of beta-chitin membranes increased the cell attachment and spreading suggesting that beta-chitin-HAp composite membranes can be used for tissue engineering applications.     

A Novel Multifunctional Crosslinking PVA/CMCS Hydrogel Containing Cyclic Peptide Actinomycin X2 and PA@Fe with Excellent Antibacterial and Commendable Mechanical Properties

Bacterial infected environments and resulting bacterial infections have been threatening the human health globally. Due to increased bacterial resistance caused by improper and excessive use of antibiotics, antibacterial biomaterials are being developed as alternatives to antibiotics in some cases. Herein, an advanced multifunctional hydrogel with excellent antibacterial properties, enhanced mechanical properties, biocompatibility and self-healing performance, was designed through freezing-thawing method. This hydrogel network is composed of polyvinyl alcohol (PVA), carboxymethyl chitosan (CMCS), protocatechualdehyde (PA), ferric iron (Fe) and an antimicrobial cyclic peptide actinomycin X2 (Ac.X2). The double dynamic bonds among protocatechualdehyde (PA), ferric iron (Fe) and carboxymethyl chitosan containing coordinate bond (catechol-Fe) as well as dynamic Schiff base bonds and hydrogen bonds endowed the hydrogel with enhanced mechanical properties. Successful formation of hydrogel was confirmed through ATR-IR and XRD, and structural evaluation through SEM analysis, whereas mechanical properties were tested with electromechanical universal testing machine. The resulting PVA/CMCS/Ac.X2/PA@Fe (PCXPA) hydrogel has favorable biocompatibility and excellent broad-spectrum antimicrobial activity against both S. aureus (95.3 %) and E. coli (90.2 %) compared with free-soluble Ac.X2, which exhibited subpar performance against E. coli reported in our previous studies. This work provides a new insight on preparing multifunctional hydrogels containing antimicrobial peptides as antibacterial material.     

Biomedical potential of chitosan-silver nanoparticles with special reference to antioxidant,antibacterial, hemolytic and in vivo cutaneous wound healing effects

The aim of the present study was to prepare chitosan-PVA-silver nanoparticles (CS-AgNPs) through green method. Chitosan and PVA polymers acted as stabilizing agents. DLS and TEM analyses showed that CS-AgNPs were homogeneously dispersed in matrix with an average size of 190–200?nm. The CS-AgNPs were tested for their antioxidant and antibacterial properties and the results revealed that they exhibited higher antioxidant activity than CS powder. Moreover, CS-AgNPs were characterized by a low cytotoxicity effect at 5–200?μg/ml against Chinese Hamster Ovary (CHO-K1) cells. In addition, the prepared CS-Ag NPs were found to promote significantly the wound healing, as determined by the wound contraction ratio and histological examination. A significant improvement in wound healing progression and in oxidative stress damage were observed for CS, CS-PVA and CS-AgNPs-treated wound tissues, when compared to control and CICAFLORA®-treated groups. The wound healing effect could be attributed to the antibacterial and antioxidant synergy of AgNPs and CS. Results strongly support the possibility of using CS-AgNPs for wound care applications.