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.     

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.     

The formation of strong intermolecular interactions in immiscible blends of poly(vinyl alcohol) (PVA) and lignin

The intermolecular interactions of lignin with a hydrophilic polymer, poly(vinyl alcohol) (PVA), were studied using thermal analyses and FT-IR spectroscopy of a series of PVA/hardwood kraft lignin blend fibers prepared by thermal extrusion. Although two phases are observed in this blend system, some of the lignin was closely associated with the PVA in the PVA-rich phase. The crystallinity of the PVA fraction was reduced with increasing lignin content. An interaction energy density of -9.34 cal cm(-1), calculated from melting point depression data, suggests that strong intermolecular interactions exist between PVA and lignin. FT-IR analysis indicates the formation of strong intermolecular hydrogen bonds between the hydroxyl groups of PVA and lignin. Although the PVA/lignin blend system is immiscible in the bulk, the results herein show the existence of some specific intermolecular interaction between PVA and lignin.     

Preparation and characterization of wet spun silk fibroin/poly(vinyl alcohol) blend filaments

Silk fibroin (SF)/poly(vinyl alcohol) (PVA) blend filaments were prepared by a wet spinning process. Regenerated SF and PVA were dissolved in formic acid and the dope solution exhibited good fiber formation in a methanol coagulation bath. Due to the miscibility of SF/PVA in formic acid, the filament had a smooth surface and dense structure with a circular cross-section. The crystalline structure and thermal properties were varied with different SF/PVA ratios. The mechanical properties of the filament were also controlled by blending PVA with SF. Especially, the knot strength of the SF filament, which is a very important suture property, could be significantly improved by blending with PVA.     

Compatible ternary blends of chitosan/poly(vinyl alcohol)/poly(lactic acid) produced by oil-in-water emulsion processing

Ternary compatible blends of chitosan, poly(vinyl alcohol), and poly(lactic acid) were prepared by an oil-in-water (O/W) emulsion process. Solutions of chitosan in aqueous acetic acid, poly(vinyl alcohol) (PVA) in water, and poly(lactic acid) (PLA) in chloroform were blended with a high-shear mixer. PVA was used as an emulsifier to stabilize the emulsion and to reduce the interfacial tension between the solid polymers in the blends produced. It proved to work very well because the emulsions were stable for periods of days or weeks and compatible blends were obtained when PVA was added. This effect was attributed to a synergistic effect of PVA and chitosan because the binary blends PVA/PLA and chitosan/PLA were completely incompatible. The blends were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), stress-strain tests, and Fourier transform infrared spectroscopy (FTIR). The results indicated that despite the fact that the system contained distinct phases some degree of molecular miscibility occurred when the three components were present in the blend.     

Yeast cell debris and protein partitioning in the poly(ethylene glycol)-poly(vinyl alcohol) biphasic system

Yeast cells, cell debris and protein partitioning have been investigated in the poly(ethylene glycol) (PEG) 8000/poly(vinyl alcohol) (PVA) 10,000 system. Cells and cell debris partition into the lower (PVA) phase over the pH range 4.8-7.5, and with up to 0.37 M KCl at pH 5.9. Protein partitioning is more pH-dependent in the PEG/PVA system than in the PEG/dextran system, and a significant fraction of the total protein is found at the interface at lower pH values. Significant, rapid purification of overproduced pyruvate kinase in a PEG/PVA system containing Blue Sepharose CL-6B particles is demonstrated.     

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.     

Development of films based on blends of Amaranthus cruentus flour and poly(vinyl alcohol)

The aim of this work was to develop biodegradable films based on blends of Amaranthus cruentus flour and poly(vinyl alcohol). Five different PVA types were tested. Blends with higher hydrolysis (HD) degree PVA were more resistant, showing greater tensile strength (TS) and puncture force (PF). However, the films with PVA with lower HD showed more flexibility, greater elongation at break (ELO) and greater puncture deformation (PD), with the exception of PVA 325. The latter was chosen due to it superior mechanical performance (TS = 10.2 MPa, ELO = 89.8%, PF = 9.4 N and PD = 16.3%). When films based on blends of amaranth flour and PVA 325 (10–50%) were evaluated, all mechanical properties were enhanced with increase in PVA 325 content. The solubility in water of the films made with PVA and amaranth flour decreased with increasing PVA content, reaching 44% of soluble matter for the 50% PVA film. The formation of hydrogen bonds between the blend components was confirmed by the FTIR spectra analysis.     

Effect of deacetylation on wicking behavior of co-electrospun cellulose acetate/polyvinyl alcohol nanofibers blend

Cellulose acetate (CA) nanofibers webs deserve a special attention because of their very good water retention properties. CA nanofibers based biosensor in certain application come into contact with various liquids and requires high degree of wicking rate to transport liquid to its destination. Cellulose acetate (CA)/polyvinyl alcohol (PVA) blended nanofibers were prepared via co-electrospinning using double nozzle for jetting cellulose acetate and polyvinyl alcohol independently. The CA/PVA blend nanofibers webs were deacetylated in aqueous alkaline solution to convert CA in to regenerated cellulose and to remove PVA nanofibers from the raw web. The resultant nanofibers webs were characterized by wicking rate, water contact angle, SEM and FTIR analysis. The results revealed that by varying concentration of PVA solution enhances the wicking rate. Such a nanofibers web may be used in biosensor strip and other medical applications where the high wicking rates are desired.     

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.     

Effect of gelatinization and additives on morphology and thermal behavior of corn starch/PVA blend films

The blend films of ungelatinized and gelatinized starch/polyvinyl alcohol (PVA) were prepared with a solution casting method by the introduction of additives (glycerol/urea) or not. The phase morphologies and thermal behaviors of the blends were carefully analyzed. A droplet phase was observed in the blends containing ungelatinized starch and a laminated phase was observed in the blends containing gelatinized starch. For both ungelatinized and gelatinized starch/PVA blends, the melting temperature (T(m)) (210-230°C) of PVA was detected, and the T(m) of gelatinized starch/PVA blends was higher than that of the ungelatinized starch/PVA blends. Blend films containing 16.8wt% of glycerol or urea exhibited a decreased T(m). The introduction of additives (glycerol or urea) reduced the decomposition onset temperature of the blend films. These various morphologies and thermal behaviors could be attributed to the different hydrogen bonding interaction characteristics between starch and polyvinyl alcohol at different conditions.     

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.     

Poly(vinyl alcohol) functionalized poly(dimethylsiloxane) solid surface for immunoassay

In this communication, we describe a simple and robust method for the covalent bonding of poly(vinyl alcohol) (PVA) on a silanized poly(dimethylsiloxane) (PDMS) surface. Nonspecific adsorption of proteins via hydrophobic-hydrophobic interactions of the PVA-coated surface is greatly reduced, and biomolecules can be rapidly anchored on the PVA-coated surface with high loading and uniformity. On the basis of a sandwich immunoassay with the anti-rabbit IgG and IgG pair as a model, the detection limit for IgG is down to 1 pg/mL with linearity up to 11 microg the levels often encountered in biological, forensic, and environmental samples.     

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.     

Nanofibers from blends of polyvinyl alcohol and polyhydroxy butyrate as potential scaffold material for tissue engineering of skin

Nanofibers were prepared by electrospinning from pure polyvinyl alcohol (PVA), polyhydroxybutyrate (PHB), and their blends. Miscibility and morphology of both polymers in the nanofiber blends were studied by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC), revealing that PVA and PHB were miscible with good compatibility. DSC also revealed suppression of crystallinity of PHB in the blend nanofibers with increasing proportion of PVA. The hydrolytic degradation of PHB was accelerated with increasing PVA fraction. Cell culture experiments with a human keratinocyte cell line (HaCaT) and dermal fibroblast on the electrospun PHB and PVA/PHB blend nanofibers showed maximum adhesion and proliferation on pure PHB. However, the addition of 5 wt % PVA to PHB inhibited growth of HaCaT cells but not of fibroblasts. On the contrary, adhesion and proliferation of HaCaT cells were promoted on PVA/PHB (50/50) fibers, which inhibited growth of fibroblasts.     

The plasticizing mechanism and effect of calcium chloride on starch/poly(vinyl alcohol) films

Starch/poly(vinyl alcohol) (PVA) films were prepared with calcium chloride (CaCl(2)) as the plasticizer. The micro morphology of pure starch/PVA film and CaCl(2) plasticized starch/PVA film was observed by scanning electron microscope. The interaction between CaCl(2) and starch/PVA molecules was investigated by Fourier transform infrared spectroscopy. The influence of CaCl(2) on the crystalline, thermal and mechanical properties of starch/PVA films was studied by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and tensile testing, respectively. The results indicated that CaCl(2) could interact with starch and PVA molecules and then effectively destroy the crystals of starch and PVA. Starch/PVA films plasticized with CaCl(2) became soft and ductile, with lower tensile strength and higher elongation at break compared with pure starch/PVA film. The water content of starch/PVA film would increase with the addition of CaCl(2). This is an important cause of the plasticization of CaCl(2) on starch/PVA film.     

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.     

Hydrolysis of sucrose using sulfonated poly(vinyl alcohol) as catalyst

The hydrolysis of sucrose was carried out over poly(vinyl alcohol) (PVA) with sulfonic acid groups, at 80 °C. The products of sucrose hydrolysis were glucose and fructose. A series of PVA with different crosslinking degree were prepared. It was observed that the catalytic activity of PVA matrix increases with the crosslinking degree, due to the increases of the amount of sulfonic acid groups on PVA.     

Accelerated biodegradation of poly(vinyl alcohol) by glycosidations of the hydroxyl groups or addition of sugars

Biodegradabilities of N-acetyl-d-glucosamine (GlcNAc)- (1) and chitobiose-substituted (2) poly(vinyl alcohol)s (PVA)s in a soil suspension (pH 6.5) were investigated at 25 degrees C for 40 days. Biochemical oxygen demand of 1 with a degree of substitution of 0.2-0.3 (DP = 430-480) was higher than that of PVA under the degradation condition. Size exclusion chromatography, (1)H NMR, and Fourier-transform infrared measurements of the recovered sample indicated that biodegradation of the PVA main chain was accelerated by partial glycosidation of hydroxyl groups in PVA. Similar acceleration was observed in a PVA/GlcNAc (50:50, w/w) mixture. Microbes which relate with degradation of the glycosidated polymers were grown in a culture medium including the soil suspension and the polymer as the carbon source. Polyacrylamide gel electrophoresis (SDS-PAGE) and IR measurements indicated that a cell-free extract derived from GlcNAc-substituted PVA was different from that in the PVA/GlcNAc mixture. The results suggested that the PVA main chain in GlcNAc-substituted PVA was cleaved by a different microorganism or via a mechanism different from that in the mixture. Chitobiose-substituted PVA 2 showed more enhanced acceleration, indicating that the sugar length influenced the degradability.     

Continuous separation of proteins by poly(vinyl alcohol) shielded Multichannel Flow Electrophoresis

Summary A hydrophilic polysulphone membrane spaced multicompartment electrolyzer for Multichannel Flow Electrophoresis (MFE) was developed. Application of poly(vinyl alcohol) (PVA) in MFE resulted in a 35% increase of protein transmembrane flux. Continuous separation of bovine serum albumin (BSA) and haemoglobin bovine blood (HBB) model mixture by PVA shielded MFE yielded 56mg BSA and 48mg HBB per hour. The average recovery was 65%.