Electrospun nano-fiber mats containing cationic cellulose derivatives and poly (vinyl alcohol) with antibacterial activity

Nano-fibrous mats have been successfully prepared by electrospinning of the blend solutions of cationic cellulose derivatives (PQ-4) and polyvinyl alcohol (PVA). Effects of the blending ratio and applied voltage on the morphology and diameter of the electrospun nano-fibers were investigated. The average diameter of the PQ-4/PVA blend fibers was in the range of 150–250 nm. The electrospinning process became instable and the fiber diameter distribution broadened with increasing PQ-4 content and applied voltage. The antibacterial activity of electrospun PQ-4/PVA blend mats against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus indicated potential for biomedical use.     

Electrospinning of poly(vinyl alcohol)-water-soluble quaternized chitosan derivative blend

Defect free mats containing a cationic polysaccharide, chitosan derivative such as N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (HTCC), have been prepared using electrospinning of an aqueous solution of poly(vinyl alcohol) (PVA)-HTCC blends. HTCC, a water-soluble derivative of chitosan, was synthesized via the reaction between glycidyl-trimethylammonium chloride and chitosan. Solutions of PVA-HTCC Blends were electrospun. The morphology, diameter and structure of the produced electrospun nanofibres were examined by scanning electron microscopy (SEM). The average fibre diameter was in the range of 200-600 nm. SEM images showed that the morphology and diameter of the nanofibres were mainly affected by weight ratio of the blend and applied voltage. The results revealed that increasing HTCC content in the blends decreases the average fibre diameter. These observations were discussed on the basis of shear viscosities and conductivities of the spinning solutions. Microbiological assessment showed that the PVA-HTCC mats have a good antibacterial activity against Gram-positive bacteria, Staphylococcus aureus, and Gram-negative bacteria, Escherichia coli.     

Preparation and antibacterial activity of chitosan nanoparticles

Chitosan nanoparticles, such as those prepared in this study, may exhibit potential antibacterial activity as their unique character. The purpose of this study was to evaluate the in vitro antibacterial activity of chitosan nanoparticles and copper-loaded nanoparticles against various microorganisms. Chitosan nanoparticles were prepared based on the ionic gelation of chitosan with tripolyphosphate anions. Copper ions were adsorbed onto the chitosan nanoparticles mainly by ion-exchange resins and surface chelation to form copper-loaded nanoparticles. The physicochemical properties of the nanoparticles were determined by size and zeta potential analysis, atomic force microscopy (AFM), FTIR analysis, and XRD pattern. The antibacterial activity of chitosan nanoparticles and copper-loaded nanoparticles against E. coli, S. choleraesuis, S. typhimurium, and S. aureus was evaluated by calculation of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Results show that chitosan nanoparticles and copper-loaded nanoparticles could inhibit the growth of various bacteria tested. Their MIC values were less than 0.25 microg/mL, and the MBC values of nanoparticles reached 1 microg/mL. AFM revealed that the exposure of S. choleraesuis to the chitosan nanoparticles led to the disruption of cell membranes and the leakage of cytoplasm.     

Sodium alginate/poly(vinyl alcohol)/nano ZnO composite nanofibers for antibacterial wound dressings

Sodium alginate (SA)/poly (vinyl alcohol) (PVA) fibrous mats were prepared by electrospinning technique. ZnO nanoparticles of size ∼160 nm was synthesized and characterized by UV spectroscopy, dynamic light scattering (DLS), XRD and infrared spectroscopy (IR). SA/PVA electrospinning was further carried out with ZnO with different concentrations (0.5, 1, 2 and 5%) to get SA/PVA/ZnO composite nanofibers. The prepared composite nanofibers were characterized using FT-IR, XRD, TGA and SEM studies. Cytotoxicity studies performed to examine the cytocompatibility of bare and composite SA/PVA fibers indicate that those with 0.5 and 1% ZnO concentrations are less toxic where as those with higher concentrations of ZnO is toxic in nature. Cell adhesion potential of this mats were further proved by studying with L929 cells for different time intervals. Antibacterial activity of SA/PVA/ZnO mats were examined with two different bacteria strains; Staphylococcus aureus and Escherichia coli, and found that SA/PVA/ZnO mats shows antibacterial activity due to the presence of ZnO. Our results suggest that this could be an ideal biomaterial for wound dressing applications once the optimal concentration of ZnO which will give least toxicity while providing maximum antibacterial activity is identified.f     

Rheological characterisation of a novel thermosensitive chitosan/poly(vinyl alcohol) blend hydrogel

Thermosensitive hydrogels that are triggered by changes in environmental temperature thus resulting in in situ hydrogel formation have recently attracted the attention of many investigators for biomedical applications. In the current work, the thermosensitive hydrogel was prepared through the mixture of chitosan (CS), poly(vinyl alcohol) (PVA) and sodium bicarbonate. The mixture was liquid aqueous solutions at low temperature (about 4 °C), but a gel under physiological conditions. The hydrogel was characterized by FTIR, swelling and rheological analysis. The effect of hydrogel composition and temperature on both the gel process and the gel strength was investigated from which possible hydrogel formation mechanisms were inferred. In addition, the hydrogel interior morphology as well as porosity of structure was evaluated by scanning electron microscopy (SEM). The potential of the hydrogels as vehicles for delivering bovine serum albumin (BSA) were also examined. In this study, the physically crosslinked chitosan/PVA gel was prepared under mild conditions without organic solvent, high temperature or harsh pH. The viscoelastic properties, as investigated rheologically, indicate that the gel had good mechanical strength. The gel formed implants in situ in response to temperature change, from low temperature (about 4 °C) to body temperature, which was very suitable for local and sustained delivery of proteins, cell encapsulation and tissue engineering.     

Synthesis of acyl thiourea derivatives of chitosan and their antimicrobial activities in vitro

Three different acyl thiourea derivatives of chitosan (CS) were synthesized and their structures were characterized by FT-IR spectroscopy and elemental analysis. The antimicrobial behaviors of CS and its derivatives against four species of bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Sarcina) and four crop-threatening pathogenic fungi (Alternaria solani, Fusarium oxysporum f. sp. vasinfectum, Colletotrichum gloeosporioides (Penz.) Saec, and Phyllisticta zingiberi) were investigated. The results indicated that the antimicrobial activities of the acyl thiourea derivatives are much better than that of the parent CS. The minimum value of MIC and MBC of the derivatives against E. coli was 15.62 and 62.49 microg/mL, respectively. All of the acyl thiourea derivatives had a significant inhibitory effect on the fungi in concentrations of 50-500 microg/mL; the maximum inhibitory index was 66.67%. The antifungal activities of the chloracetyl thiourea derivatives of CS are noticeably higher than the acetyl and benzoyl thiourea derivatives. The degree of grafting of the acyl thiourea group in the derivatives was related to antifungal activity; higher substitution resulted in stronger antifungal activity.     

Synthesis, characterization, cytotoxicity and antibacterial studies of chitosan, O-carboxymethyl and N,O-carboxymethyl chitosan nanoparticles

Chitosan (CS) is a naturally occurring biopolymer. It has important biological properties such as biocompatibility, antifungal and antibacterial activity, wound healing ability, anticancerous property, anticholesteremic properties, and immunoenhancing effect. Recently, CS nanoparticles have been used for biomedical applications. However, due to the limited solubility of CS in water its water-soluble derivatives are preferred for the above said applications. In this work, the nanoparticles of CS and its water-soluble derivatives such as O-carboxymethyl chitosan (O-CMC) and N,O-carboxymethyl chitosan (N,O-CMC) was synthesized and characterized. In addition, cytotoxicity and antibacterial activity of the prepared nanoparticles was also evaluated for biomedical applications.     

Pyranones from kiwi-associated fungus Fusarium tricinctum and their antibacterial activity

Four new pyrone derivatives, fusaritricins A–D (1−4), together with five known analogues, were obtained from the kiwi endophytic fungus Fusarium tricinctum. Their structures were established by extensive spectroscopic data analysis and their absolute configurations were determined by quantum chemical calculations. Compounds 1, 2, 3, and 9 exhibited antibacterial activity against plant pathogen Pseudomonas syringae pv. Actinidiae (Psa) with MIC values of 128, 128, 64, and 64 µg/mL, respectively. This is the first report of anti-Psa activity of pyrone derivatives.     

Modification of chitosan membrane with poly(vinyl alcohol) and biocompatibility evaluation

This work aimed to overcome chitosan (CS) membrane' drawbacks: mainly stiffness and hydrophobic surface by adding poly(vinyl alcohol) (PVA) and evaluate their biocompatibility. The chemical structure, crystalline and thermal properties were studied by FT-IR, XRD and DSC. The mechanical properties and wettability of CS/PVA membranes were studied by tensile test and static contact angle measurement. In vitro biocompatibility was also evaluated by MTS cytotoxicity assay and SEM examination. The results suggest that adding PVA into CS membrane could greatly improve CS membrane's flexibility and wettability. All the membranes prepared were biocompatible and have potential applications in GTR technology.     

Preparation of single or double-network chitosan/poly(vinyl alcohol) gel films through selectively cross-linking method

A selectively cross-linking method, which is based on the “di–diol” interaction between poly(vinyl alcohol) and borate and the strong electrostatic interaction between chitosan and tripolyphosphate, was developed. Chitosan/poly(vinyl alcohol) films cross-linked separately with borate, tripolyphosphate and borate/tripolyphosphate were then prepared in terms of this method. Water vapor permeation, mechanical strength, surface morphology and molecular interactions of the films were studied by water permeation test, texture test, atomic force microscopy and ATR-FTIR spectroscopy. With the introduction of cross-linking structure, there is a large improvement in elastic modulus from 271 ± 14.2 to 551 ± 14.7 MPa and a large decrease in water vapor permeability from (5.41 ± 0.21) × 10⁻⁷ g/m h Pa to (3.12 ± 0.24) × 10⁻⁷ g/m h Pa of chitosan/poly(vinyl alcohol) films. The surface morphology of the cross-linked films exhibits a nanoparticle aggregation structure. The size and aggregation behavior of these nanoparticles are strongly related to the type of cross-linker. Furthermore, ATR-FTIR results indicate that strong interaction between polymer matrix and cross-linker exists in our system. This work provides a simple and efficient way to prepare chitosan/poly(vinyl alcohol) films with controllable network structure.     

Electrospun water-soluble carboxyethyl chitosan/poly(vinyl alcohol) nanofibrous membrane as potential wound dressing for skin regeneration

Biocompatible carboxyethyl chitosan/poly(vinyl alcohol) (CECS/PVA) nanofibers were successfully prepared by electrospinning of aqueous CECS/PVA solution. The composite nanofibrous membranes were subjected to detailed analysis by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). SEM images showed that the morphology and diameter of the nanofibers were mainly affected by the weight ratio of CECS/PVA. XRD and DSC demonstrated that there was strong intermolecular hydrogen bonding between the molecules of CECS and PVA. The crystalline microstructure of the electrospun fibers was not well developed. The potential use of the CECS/PVA electrospun fiber mats as scaffolding materials for skin regeneration was evaluated in vitro using mouse fibroblasts (L929) as reference cell lines. Indirect cytotoxicity assessment of the fiber mats indicated that the CECS/PVA electrospun mat was nontoxic to the L929 cell. Cell culture results showed that fibrous mats were good in promoting the cell attachment and proliferation. This novel electrospun matrix would be used as potential wound dressing for skin regeneration.     

Environmentally friendly films based on chitosan and tetrahydrocurcuminoid derivatives exhibiting antibacterial and antioxidative properties

Environmentally friendly films exhibiting both antibacterial and antioxidative properties were elaborated from chitosan and tetrahydrocurcuminoids (THCs). Two tetrahydrocurcuminoids, THC1 (5-hydroxy-1,7-bis(4-hydroxy-3-methoxyphenyl)hept-4-en-3-one) and THC2 (5-hydroxy-1,7-bis(4-hydroxy-3,5-dimethoxyphenyl)hept-4-en-3-one), were incorporated into a chitosan film. THC1 could be prepared from natural curcumin extracted from turmeric roots (Curcuma longa L.). The resulting tetrahydrocurcuminoid–chitosan films exhibited a high free-radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) in methanol, which was due to a progressive release of the THCs into the solvent. The release kinetics was governed both by molecular interactions between chitosan and THCs and probably by electrostatic forces between the ammonium units in chitosan and the aromatic rings in THCs. These interactions were clearly evidenced by the presence of new absorption bands in the visible regions of the electronic absorption spectra of the THCs. The molecular nature of these interactions was shown using glucosamine, the main monomer of chitosan. When associated with THCs, chitosan retained its bioactivity against Listeria innocua; THCs alone were not bioactive enough against listerial strains.     

Antibacterial activity of quaternary ammonium chitosan containing mono or disaccharide moieties: Preparation and characterization

The 9 quaternary ammonium chitosans containing monosaccharides or disaccharides moieties were successfully synthesized by reductive N-alkylation then quaternized by N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride (Quat-188). The chemical structures of quaternary ammonium chitosan derivatives were characterized by ATR-FTIR and ¹H NMR spectroscopy. The degree of N-substitution (DS) and the degree of quaternization (DQ) were determined by ¹H NMR spectroscopic method. It was found that the DS was in the range of 12–40% while the DQ was in the range of 90–97%. The results indicated that the O-alkylation was occured in this condition. Moreover, all quaternary ammonium chitosan derivatives were highly water-soluble at acidic, basic, and neutral pH. Minimum inhibitory concentration (MIC) antibacterial studies of these materials were carried out on Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria compared to quaternary ammonium N-octyl and N-benzyl chitosan derivatives. The quaternary ammonium mono and disaccharide chitosan derivatives showed very high MIC values which were in the range of 32 to >256 μg/mL against both bacteria. Also it was found that the antibacterial activity decreased with increasing the DS. This was due to the increased hydrophilicity of mono and disaccharide moieties. On the other hand, the low MIC values (8–32 μg/mL) were obviously observed when the DS of quaternary ammonium N-octyl and N-benzyl chitosan derivatives was lower than 18%. The results showed that the presence of hydrophobic moiety such as the N-benzyl group enhanced the antibacterial activity compared to the hydrophilic moiety against both bacteria.     

Finishing of cotton fabrics with poly (N-vinyl-2-pyrrolidone) to improve their performance and antibacterial properties

Cotton fabric was thermally crosslinked with poly (N-vinyl-2-pyrrolidone) (PVP) at different conditions including temperature, time, PVP concentrations and molecular weights. Results indicated that treating the cotton fabrics with 4% aqueous solution of PVP of molecular weight 10,000 Dalton followed by drying at 85 °C for 5 min then curing at 160 °C for 3 min results in crosslinking as will as an improvement in some performance properties of that fabrics such as resiliency, tensile strength, and acid dyeability. Post-treating PVP crosslinked fabric with 5% iodine in ethanol solution for 5 h at 50 °C imparts antibacterial activity against Staphylococcus aureus and Escherichia coli. Moreover, incorporation of PVP in the easy-care finishing of cotton fabrics, as polymer additive, with N,N-dimethylol 4,5-dihydroxyethylene urea as a crosslinker enhances some of the performance properties of finished fabrics such as the nitrogen content, tensile strength and acid dyeability along with decreasing resiliency as well as whiteness index, whereas the ester crosslinking with citric acid, in presence of PVP, enhances resilience, tensile strength and whiteness indices accompanied with a reduction in the %N of the treated fabrics. Infra red spectrum of PVP crosslinked fabric as well as EDX analysis of loaded iodine on PVP crosslinked cotton fabric were investigated.     

Wheat gluten-thiolated poly(vinyl alcohol) blends with improved mechanical properties

A multifunctional macromolecular thiol (TPVA) obtained by esterification of poly(vinyl alcohol) (PVA) with 3-mercaptopropionic acid was characterized by a combination of NMR, IR, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC), and was used as a wheat gluten (WG) reactive modifier. The effect of TPVA molecular weight (M(w) = 2000, 9500, 50 000, and 205 000) and blend composition (5, 20, and 40% w/w TPVA/WG) on the mechanical properties of compression-molded bars indicates that TPVA/WG blends increase the fracture strength by up to 76%, the elongation by 80%, and the modulus by 25% above WG. In contrast, typical WG additives such as glycerol and sorbitol improve flexibility but decrease modulus and strength. Preliminary investigations of suspension rheology, water uptake, molecular weight distribution and electron microscopy of TPVA/WG and PVA/WG blends illustrate the different protein interactions with PVA and TPVA. Further work is underway to determine whether TPVA and WG form protein conjugates or microphase-separated morphologies.     

Synthesis and properties of carrageenan grafted copolymer with poly(vinyl alcohol)

The aim of this work was to prepare a carrageenan-g-poly(vinyl alcohol) (CG-g-PVA) polymer using potassium persulphate as an initiator. The effect of different ratios of the polymer blends on the parameters of the grafted polymer was investigated. The grafting ratio decreased with an increase of the CG content in the graft copolymer. The resulting CG-g-PVA was characterized by ATR-FTIR, tensile strength, elongation at break, swelling ratio, contact angle and biodegradation in soil. From the ATR-FTIR the 3,6-anhydride-galactose of the CG showed a peak at 927 cm⁻¹ that was absent in the CG-g-PVA and the ether linkage of PVA-g-CG between the hydroxyl group of PVA and the 3,6-anhydride-galactose of CG showed a peak at 1089 cm⁻¹ in the graft copolymer. The tensile strength and elongation at break decreased with an increase of the CG due to its phase separation. The highest tensile strength was observed at 2:8 CG/PVA. In addition, the swelling ratio decreased and the contact angle increased as a function of the increase of the CG in the grafted copolymer. The best ratio of CG-g-PVA was 2:8 CG/PVA. This graft copolymer was easily biodegraded in natural soil.     

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.     

Electrospinning of carboxymethyl chitin/poly(vinyl alcohol) nanofibrous scaffolds for tissue engineering applications

A novel fibrous membrane of carboxymethyl chitin (CMC)/poly(vinyl alcohol) (PVA) blend was successfully prepared by electrospinning technique. The concentration of CMC (7%) with PVA (8%) was optimized, blended in different ratios (0–100%) and electrospun to get nanofibers. Fibers were made water insoluble by chemical followed by thermal cross-linking. In vitro mineralization studies identified the ability of formation of hydroxyapatite deposits on the nanofibrous surfaces. Cytotoxicity of the nanofibrous scaffold was evaluated using human mesenchymal stem cells (hMSCs) by the MTT assays. The cell viability was not altered when these nanofibrous scaffolds were pre-washed with phosphate buffer containing saline (PBS) before seeding the cells. The SEM images also revealed that cells were able to attach and spread in the nanofibrous scaffolds. Thus our results indicate that the nanofibrous CMC/PVA scaffold supports cell adhesion/attachment and proliferation and hence this scaffold will be a promising candidate for tissue engineering applications.     

Swelling and flow properties of tubular poly(vinyl alcohol) gels

Swelling and flow properties of tubular poly(vinyl alcohol) (PVA) hydrogels prepared with the cooling method were investigated using an inflation testing method. When the tubular hydrogel in liquid paraffin was inflated by using liquid paraffin as a pressure transmitting medium, namely in the case that the liquids inside and outside the gel are both liquid paraffin (P/P combination), the gel showed a slight volume change determined by Poisson's ratio of the gel. When the gel in water was inflated by liquid paraffin (P/W combination), the gel swelled to large extent compared with the case of P/P. The hydrogel in W/W combination, namely in the situation that the gel was immersed in water and also inflated by water, showed a very large volume change if the comparison was done at the same pressure. The origin of the volume change in P/P, P/W and W/W combinations is discussed. The volume change in P/P was governed by the Poisson ratio as a material constant (mu 0) of the PVA gels, and the gels swelled by the change in the application of pressure (or deformation) in P/W. The volume change in W/W was closely related to the flow of solvent in the gel.     

Quaternization of N-aryl chitosan derivatives: synthesis, characterization, and antibacterial activity

Chemical modification of chitosan by introducing quaternary ammonium moieties into the polymer backbone renders excellent antimicrobial activity to the adducts. In the present study, we have synthesized 17 derivatives of chitosan consisting of a variety of N-aryl substituents bearing either electron-donating or electron-withdrawing groups. Selective N-arylation of chitosan was performed via Schiff bases formed by the reaction between the 2-amino groups of the glucosamine residue of chitosan with aromatic aldehydes under acidic conditions, followed by reduction of the Schiff base intermediates with sodium cyanoborohydride. Each of the derivatives was further quaternized using N-(3-chloro-2-hydroxypropyl)trimethylammonium chloride (Quat-188) as the quaternizing agent that reacted with either the primary amino or hydroxyl groups of the glucosamine residue of chitosan. The resulting quaternized materials were water soluble at neutral pH. Minimum inhibitory concentration (MIC) antimicrobial studies of these materials were carried out on Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria in order to explore the impact of the extent of N-substitution (ES) on their biological activities. At ES less than 10%, the presence of the hydrophobic substituent, such as benzyl and thiophenylmethyl, yielded derivatives with lower MIC values than chitosan Quat-188. Derivatives with higher ES exhibited reduced antibacterial activity due to low quaternary ammonium moiety content. At the same degree of quaternization, all quaternized N-aryl chitosan derivatives bearing either electron-donating or electron-withdrawing substituents did not contribute antibacterial activity relative to chitosan Quat-188. Neither the functional group nor its orientation impacted the MIC values significantly.