SURFACE MODIFICATION OF BIODEGRADABLE ANTI-ADHESIVE MEMBRANES WITH POLYVINYL ALCOHOL TO IMPROVE BIOCOMPATIBILITY

Degradation of polyvinyl alcohol in aqueous solutions using UV/oxidant process

Performance of UV/S2O82− process in degrading polyvinyl alcohol in aqueous solutions

This paper is about the degradation of polyvinyl alcohol (PVA) in aqueous solutions using a H2O2/Mn(II) system. Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) were applied to analyze the degradation products of PVA, and the results revealed that the backbone chain of PVA could be effectively broken and oxidized. Several unsaturated degradation products, including carboxylic acids, ketones, aldehydes, olefins, and alkynes were also detected and identified by gas chromatography-mass spectrometry (GC-MS), which indicated that higher treatment temperatures would considerably promote the generation of lower molecular weight degradation products. According to the work presented in this paper, the degradation efficiency of PVA increased from 55 % at 60 oC to 99 % at 90 oC after treatment when the initial PVA concentration was 5 %, at pH=3 with a H2O2 and Mn(II) dose of 100 ml/l and 0.6 mol/l, respectively. In addition, kinetic modeling indicated that the experimental results were best fitted by the Page-modified model with an activation energy of 48.78 kJ/mol.

UV/S2O82− process for degrading polyvinyl alcohol in aqueous solutions

This study evaluates the performance of an innovative paired photoelectrochemical oxidative system fabricated in our laboratory to determine the removal efficiency of polyvinyl alcohol (PVA) in aqueous solutions. An innovative paired photoelectrochemical oxidative system employed metal redox mediators with high redox potential for anodic oxidation (MEO process) and UV assisted photoelectrochemical oxidation (PEO process) for cathodic oxidation in a divided electrochemical cell. Several parameters were investigated to characterize the removal efficiency of PVA, such as the current density, initial Ce(III) concentration, nitric acid concentration, oxygen flow rate, and UV irradiation intensity. The effects of these parameters on the specific energy consumption were also investigated. Additionally, the conversion yield of Ce(IV) concentration and the electrogeneration of H2O2were calculated in this study. The optimum current density, initial Ce(III) concentration, nitric acid concentration, oxygen flow rate, and UV irradiation intensity were found to be 3 mA cm−2, 0.01 M, 0.3 M, 500 cm3 min−1, and 1.2 mW cm−2, respectively. The synergistic effect of combination process of MEO and PEO would be as a promising alternative for the removal efficiency of PVA.

Bionic artificial penile Tunica albuginea

This investigation evaluates the effectiveness of UV-365 nm/S2O8 2− process in degrading polyvinyl alcohol in aqueous solutions. The effects of pH, Na2S2O8 dosage, and temperature on the degradation efficiency of polyvinyl alcohol were studied. Under acidic conditions, the degradation efficiency of polyvinyl alcohol exceeded that under alkaline conditions. Additionally, a higher Na2S2O8 dosage and a higher temperature were associated with a higher degradation efficiency of polyvinyl alcohol. The degradation rates of polyvinyl alcohol followed a pseudo-first-order kinetic model. Moreover, the observed degradation rate coefficient increased from 0.0078 to 0.4081 min−1 when the temperature was increased from 10 to 55 °C. Also, the activation energy estimated using the observed degradation rate coefficients and the Arrhenius equation was 64 kJ/mol. At UV-365 nm, pH 3, an Na2S2O8 dosage of 0.06 g/L, a temperature of 55 °C, and an initial polyvinyl alcohol concentration of 20 mg/L, around 100 % of polyvinyl alcohol was degraded, indicating that UV-365 nm/S2O8 2− process has great potential in degrading polyvinyl alcohol in aqueous solutions.

Radiolytic formation of Ag clusters in aqueous polyvinyl alcohol solution and hydrogel matrix

1. In the spray method of quenching a new quenchant consisting of an 8–12% aqueous solution of triethanol amine and a 0.2–0.8% aqueous solution of polyvinyl alcohol (triethanol amine-polyvinyl alcohol aqueous solutions) in quenching capacity occupies an intermediate place between an oil spray and a water bath but closer to an oil spray. 2. By changing the polyvinyl alcohol concentration it is possible to regulate within wide limits the quenching capacity of triethanol amine-polyvinyl alcohol aqueous solutions for the purpose of providing high-quality hardening of parts of any shape of different steels from straight carbon to multialloy ones. 3. Triethanol amine-polyvinyl alcohol aqueous solutions possess high technical and service reliability, are inexpensive and safe in operation, and may be recommended for hardening practically any parts in various branches of industry.

The ultrasonic velocity and the absorption have been measured over the 5–45 Mc./sec. frequency range for aqueous solutions of polyvinyl alcohol by means of an ultrasonic pulse technique which was similar in principle to that used by Pinkerton (Proc. Phys. Soc. B62, 286 (1949)). The temperature varied over the 3–70°C range. The velocity-versus-temperature curves have been found to be convex upwards, like that of pure water, but the peak shifts upwards and to the lower-temperature side with an increase in the concentration. The ultrasonic absorptions of aqueous solutions of partly-saponified polyvinyl alcohol have been found to be larger than those of perfectly-saponified alcohol at the same concentrations. Two relaxation mechanisms have been found for each sample. For the solutions of the perfectly-saponified sample, the first relaxation frequency, f1, is 35 Mc./sec. at 12°C, while the second relaxation frequency f2 is 40 Mc./sec. at 60°C, for example. On the other hand, these values have been found to be nearly equal for the solutions of the partly-saponified sample. The activation energy, ΔH2, obtained from the temperature dependence of f2 is about 4 kcal./mol., irrespective of the quantity of resuidal acetate groups, and the ΔH1 value forf1 is of the order of 10 kcal./mol.

The demand for tissue scaffolds to support the repair, regeneration, and restoration of damaged tissues is rapidly growing. Scaffolds fabricated using the electrospinning technique are particularly significant in tissue engineering due to their ability to provide micro- to nano-scale porosity and a large surface area. This study focuses on developing tissue scaffolds with enhanced cell adhesion, biodegradability, and tensile strength by employing aqueous solutions of polyvinyl alcohol (PVA), a biocompatible and biodegradable synthetic polymer; gelatin (GEL), a natural polymer that offers binding sites conducive to cell adhesion and differentiation; and synthesized bioceramics, all integrated through the electrospinning process. Composite tissue scaffolds were engineered by incorporating 1% to 3% GEL into the PVA solution, followed by the addition of 1% bioceramics to the 1% GEL-enriched PVA. The composite formulation not only emulates the extracellular matrix as a biomimetic strategy but also goes beyond merely enhancing ossification. Comprehensive structural, morphological, mechanical, and thermal characterizations were conducted to analyze the properties of the scaffolds containing the synthesized bioceramics. The tensile strengths of the fabricated nanocomposites were determined to be 6.25 MPa for 10:0 (PVA:GEL), 7.45 MPa for 10:1 (PVA:GEL), 8.01 MPa for 10:3 (PVA:GEL), and 8.22 MPa for 10:1:1 (PVA:GEL:Bioceramics), respectively, indicating a progressive enhancement in mechanical properties with the incorporation of GEL and bioceramics. The results demonstrate the successful production of a potential biomaterial with ideal properties for tissue engineering applications. These composite scaffolds, providing a conducive environment for cell adhesion and exhibiting excellent mechanical properties, are anticipated to be suitable for dental applications as an intermediate layer which may support bone and connective tissue formation.

The methods for producing cryogels and hydrogels from viscous aqueous solutions of polyvinyl alcohol (PVA) and their rheological properties are considered. Freezing an aqueous solution of polyvinyl alcohol, its exposure to negative temperature and subsequent thawing at a positive temperature lead to the formation of elastic cryogels. Chemical cross-linking of individual PVA molecules into spatial networks is accompanied by the transformation of aqueous solutions into hydrogels. Sodium tetraborate and glyoxal were used to structurise the polymer solutions. It has been determined that the interaction of these reagents with the functional groups of the polymer causes an increase in the viscosity of three-component systems “PVA - glyoxal - water” and “PVA - sodium tetraborate - water” with time. The kinetics of gel formation in the products of chemical reactions was investigated at different concentrations. It is shown that the viscosity of the studied systems increases with an increase in the concentrations of low-molecular reagents in both cases (PVA - glyoxal and PVA - sodium tetraborate). Hydrogels formed at a positive temperature were subjected to additional freezing-thawing cycle, cryogels were obtained, and their rheological properties were studied. The elastic properties of cryogels were determined to be more clearly pronounced than those of hydrogels. Hydrogels can be used as instantaneous gel-forming systems to protect from dangerous chemicals and to make waterproof barriers in hydraulic structures, as the elastic properties are enhanced after cryogenic exposure.

There is currently a demand for anti-adhesive materials that are capable of preventing the formation of intra-abdominal adhesions. In this study, electrospun poly(lactide-co-glycolide) scaffolds were dip-coated in aqueous solutions of polyvinyl alcohol with concentrations of 3 wt.%, 6 wt.% and 9 wt.% to obtain a nontoxic and anti-adhesive biomedical material. The viscosities of the applied 3 wt.%, 6 wt.% and 9 wt.% polyvinyl alcohol solutions were 7.7 mPa∙s, 38.2 mPa∙s and 180.8 mPa∙s, respectively, and increased exponentially. It is shown that increasing the viscosity of the polyvinyl alcohol solution from 6 wt.% to 9 wt.% increases the thickness of the polyvinyl alcohol layer from (3.32 ± 0.97) µm to (8.09 ± 1.43) µm. No pronounced polyvinyl alcohol layer can be observed on samples dip-coated in 3 wt.% PVA solution. Increasing the viscosity of the polyvinyl alcohol solution from 3 wt.% to 9 wt.% increases the mechanical properties of the poly(lactide-co-glycolide) samples by a factor of 1.16–1.45. Cytotoxicity analysis of all samples reveals that none is toxic to 3T3-L1 fibroblast cells. A cell adhesion assay indicates that the anti-adhesion properties increase with increasing viscosity of the polyvinyl alcohol solution and the thickness of the polyvinyl alcohol layer on the poly(lactide-co-glycolide) scaffolds. Fluorescence images of the cells show that as the thickness of the polyvinyl alcohol coating increases, the number of cells decreases, and they do not cover the surface of the samples and form spherical three-dimensional agglomerates. The highest mechanical and anti-adhesion properties are obtained with the poly(lactide-co-glycolide) scaffold sample dip-coated in the 9 wt.% polyvinyl alcohol solution. This is because this sample has the thickest polyvinyl alcohol coating.

The concentration of the binder is a key factor affecting the quality of 3D-printed bone scaffolds. This study analyzed the influence of polyvinyl alcohol (PVA) aqueous solution concentration on the properties of hydroxyapatite (HA)/β-tricalcium phosphate (β-TCP) bone scaffolds from both microscopic and macroscopic perspectives using molecular dynamics (MD) simulations and experimental research. In the MD simulations, the changes in chain length corresponding to different concentrations were used to analyze the microscopic interactions between PVA and the powder material system. In the experiments, the solid content, zeta potential, and extrusion rheological properties of the slurry were analyzed under PVA concentrations ranging from 5% to 15% by mass. Bone scaffolds were then fabricated using 3D printing and freeze-drying processes, and the changes in porosity, mechanical properties, dimensional shrinkage, and swelling effect of the scaffolds were examined. Finally, the biological properties of the scaffolds were verified through in vitro experiments. The results showed that the hydrogen bonds and ionic bonds formed between PVA and the powder materials are the main forces for adhesion, and the increase in chain length, which leads to an increase in Cauchy pressure, enhances the basic mechanical properties of the material. Slurries with higher PVA concentrations have higher solid content and shear-thinning capabilities, ensuring better printability, and the resulting bone scaffolds exhibit higher mechanical properties and drying shrinkage characteristics. However, this also leads to lower porosity and swelling rates. In vitro experiments revealed that an increase in PVA aqueous solution concentration results in decreased porosity and ion concentration of the bone scaffolds, thereby reducing their bioactivity. The conclusions drawn from this study can be used to predict the performance of slurries and bone scaffolds at different binder concentrations, providing a theoretical basis for the selection of binder concentration in 3D-printed bone scaffolds.

Performance of silty sand reinforced with aqueous solution of polyvinyl alcohol subjected to freeze-thaw cycles