Biocompatibility of electrospun cell culture scaffolds made from balangu seed mucilage/PVA composites

Synthesis of Balangu (Lallemantia royleana) seed mucilage (BSM) solutions combined with polyvinyl alcohol (PVA) was studied for the purpose of producing 3D electrospun cell culture scaffolds. Production of pure BSM nanofibers proved to be difficult, yet integration of PVA contributed to a facile and successful formation of BSM/PVA nanofibers. Different BSM/PVA ratios were fabricated to achieve the desired nanofibrous structure for cell proliferation. It is found that the optimal bead-free ratio of 50/50 with a mean fiber diameter of ≈180 nm presents the most desirable scaffold structure for cell growth. The positive effect of PVA incorporation was approved by analyzing BSM/PVA solutions through physiochemical assays such as electrical conductivity, viscosity and surface tension tests. According to the thermal analysis (TGA/DSC), incorporation of PVA enhanced thermal stability of the samples. Successful fabrication of the nanofibers is verified by FT-IR spectra, where no major chemical interaction between BSM and PVA is detected. The crystallinity of the electrospun nanofibers is investigated by XRD, revealing the nearly amorphous structure of BSM/PVA scaffolds. The MTT assay is employed to verify the biocompatibility of the scaffolds. The cell culture experiment using epithelial Vero cells shows the affinity of the cells to adhere to their nanofibrous substrate and grow to form continuous cell layers after 72 h of incubation.

Aqueous polyvinyl alcohol solution foaming at different molecular masses

Objectives. Investigation of aqueous polyvinyl alcohol (PVA) foaming process and the influence of its water solution structure, when possessed of different molecular weights and concentrations, on foaming multiplicity.Methods. Solution foaming analysis was performed on the data of dynamic light scattering obtained on the Zetasizer Nano particle analyzer.Results. In this work, the foaming ability and foaming multiplicity of aqueous PVA solutions (as a main component for obtaining special-purpose foams) have been studied. It is shown that PVA solutions in water are colloidal dispersed systems consisting of different-sized associates (from 4.8 to 68.1 nm), depending on the molecular weight of PVA. Dependencies of aqueous PVA solution foaming multiplicities on the concentration, molecular weight, and solution temperature were given. Optimal values of concentration and molecular PVA weight, as well as optimal foaming process conditions from aqueous PVA solutions, were established.Conclusions. Increasing PVA concentrations in aqueous solutions cause foaming multiplicity to decrease for all molecular weights by 1.5 times, and increasing molecular weight increases foaming multiplicity by 2 times. The foaming ratio of aqueous PVA solutions with different concentrations and molecular weights (depending on a solution temperature characterized by a maximum of 30 °C) is associated with decreased viscosity and surface tension.

Synthesis and Characterization of N-Isopropylacrylamide Microspheres as pH Sensors

Swellable polymer microspheres that respond to pH were prepared by free radical dispersion polymerization using N-isopropylacrylamide (NIPA), N,N′-methylenebisacrylamide (MBA), 2,2-dimethoxy-2-phenylacetylphenone, N-tert-butylacrylamide (NTBA), and a pH-sensitive functional comonomer (acrylic acid, methacrylic acid, ethacrylic acid, or propacrylic acid). The diameter of the microspheres was between 0.5 and 1.0 μm. These microspheres were cast into hydrogel membranes prepared by mixing the pH-sensitive swellable polymer particles with aqueous polyvinyl alcohol (PVA) solutions followed by crosslinking with glutaric dialdehyde for use as pH sensors. Large changes in the turbidity of the PVA membrane were observed as the pH of the buffer solution in contact with the membrane was varied. These changes were monitored by UV–visible absorbance spectroscopy. Polymer swelling of many NIPA copolymers was reversible and independent of the ionic strength of the buffer solution in contact with the membrane. Both the degree of swelling and the apparent pKa of the polymer microspheres increased with temperature. Furthermore, the apparent pKa of the polymer particles could be tuned to respond sharply to pH in a broad range (pH 4.0–7.0) by varying the amount of crosslinker (MBA) and transition temperature modifier (NTBA), and the amount, pKa, and hydrophobicity of the pH-sensitive functional comonomer (alkyl acrylic acid) used in the formulation. Potential applications of these polymer particles include fiber optic pH sensing where the pH-sensitive material can be immobilized on the distol end of an optical fiber.

Affordable Magnetic Hydrogels Prepared from Biocompatible and Biodegradable Sources

Magnetic hydrogels composed of poly(vinyl alcohol) (PVA)/water-soluble tricarboxy cellulose (CO)/magnetic fluids (MFs) have been prepared by a freeze–thaw cycle technique. The system designed here combines the renewability and biocompatibility aspects of PVA and CO, as well as the magnetic properties of MFs, thereby offering special properties to the final product with potential applications in medicine. In the first step, the water-soluble CO is synthesized using a one-shot oxidation procedure and then the aqueous solutions of CO are mixed with PVA solutions and magnetic fluids in the absence of any additional cross-linking agent. The magnetic hydrogels were thoroughly investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), magnetometry (VSM), and thermogravimetric analysis. The morphological results show an excellent distribution of magnetic particles and CO inside the PVA matrix. The VSM results show that the magnetic hydrogels possess superparamagnetic properties.

Physicochemical Properties of Solutions of Polyvinyl Alcohol (PVA) of Different Molecular Weights

The physicochemical properties (surface tension, dynamic viscosity, crystallization and melting temperatures) of polyvinyl alcohol solutions of molecular weight 9, 31 and 72 kDa have been studied. The surface tension and the critical concentration of micelle formation were determined by the method of stalogometry, and the dynamic viscosity was determined using an Oswald viscometer. The crystallization and melting temperatures were determined in a cooled modified chamber of the UOP-6 software freezer at a rate of 2°C/min. Cryomicroscopic studies were carried out on a polarizing microscope "MIN-8". The surface tension reflects the interaction of PVA solutions with the lipid layer of biomembranes and indicates the hydrophobic properties of substances. The viscosity of PVA solutions characterizes their interaction with water molecules and reflects hydrophilic interactions. The purpose of the study is to determine the physicochemical properties of PVS that characterize the hydrophilic-hydrophobic interactions in the studied solutions and the micelle formation of PVА solutions of different molecular weights. Materials and methods. Studies of the dynamic viscosity and density of 0.1%-1% PVA solutions of molecular weight 9, 31 kDa showed that these parameters increase with increasing PVA concentration, which leads to increased hydrophilicity of the solutions. Results and discussion. It was shown that the surface tension of PVA solutions decreases with increasing concentration, which leads to a decrease in the hydrophobic properties of the polymer. It was found that in 0.5% PVА solutions of molecular weight 9 and 31 kDa the crystallization and melting temperatures decrease from -5 to -6°C. At these temperatures, crystallization and melting of the solutions begin. Conclusion. The study of micelle formation in PVА solutions of different molecular masses was carried out, surface tension isotherms were constructed, and the break point on the isotherm corresponding to the CCM was determined. The values of the critical concentration of micelle formation of PVА of molecular masses 9, 31, 72 kDa were determined. Hydrophobic links of PVА of molecular masses 9 and 31 kDa form hydrophobic cavities in the micelle structure, which can reduce recrystallization activity

Fabrication and Characterization of Nanocomposite Flexible Membranes of PVA and Fe3O4

Composite polymer membranes of poly(vinyl alcohol) (PVA) and iron oxide (Fe3O4) nanoparticles were produced in this work. X-ray diffraction measurements demonstrated the formation of Fe3O4 nanoparticles of cubic structures. The nanoparticles were synthesized by a coprecipitation technique and added to PVA solutions with different concentrations. The solutions were then used to generate flexible membranes by a solution casting method. The size and shape of the nanoparticles were investigated using scanning electron microscopy (SEM). The average size of the nanoparticles was 20±9 nm. Raman spectroscopy and Fourier-transform infrared spectroscopy (FTIR) were utilized to investigate the structure of the membranes, as well as their vibration modes. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrated the thermal stability of the membranes and the crystallinity degree. Electrical characteristics of the thin membranes were examined using impedance spectroscopy as a function of the nanoparticles’ concentrations and temperatures. The resistivity of the fabricated flexible membranes was possible to adjust by controlled doping with suitable concentrations of nanoparticles. The activation energy decreased with the nanoparticles’ concentrations due to the increase in charge carriers’ concentrations. Therefore, the fabricated membranes may be applied for practical applications that involve the recycling of nanoparticles for multiple application cycles.

Effect of Concentration and Nozzle-Collector Distance on the Morphology of Nanofibers

Electrospinning is a method for making nanofibers by utilizing an electric field produced by high voltage. Electrospinning process is influenced by several factors including the concentration of the solution, conductivity, viscosity, volatility, surface tension, electric field strength between the needle and the collector, feed / flow rate and environmental conditions which include temperature, humidity and air composition. Electrospinning parameters are used to optimize the size of the nanofiber, concentration of the solution and the distance of the nozzle to collector. In the process of electrospinning PVA solutions that are handled by high dc voltage gets an electrostatic force and electric field. The solution will elongate to form a Taylor cone, then a jet of polymer will undergo thinning and evaporation to form fibers in the collector. The results of morphological analysis using scanning electron microscopy (SEM) showed that the smallest nanofiber was obtained at a solution concentration of 5%, dc high voltage10 kV, and the distance of the nozzle to collector was 15 cms.

Evaluation of Repellent Effectiveness of Polyvinyl Alcohol/Eucalyptus globules Nanofibrous Membranes against Forcipomyia taiwana

This study aims to develop nanofibrous membranes where Eucalyptus globules oil (EGO) is wrapped in polyvinyl alcohol (PVA). The EGO-based nanofibrous membranes are then evaluated for the protection against Forcipomyia taiwana (F. taiwana). In the first stage, the PVA solutions are formulated with different concentrations and are measured for viscosity and electrical conductivity. In the next stage, PVA solution and EGO are blended at different ratios and electrospun into PVA/EGO nanofibrous membranes (i.e., EGO-based repellent). In this study, a PVA concentration of 14 wt% has a positive influence on fiber formation. Furthermore, the finest nanofibers of 291 nm are presented when the voltage is 15 kV. The repellent efficacy can reach 80% in a 60-min release when the repellent is composed of a PVA/oil ratio of 90/10. To sum up, the nanofibrous membranes of essential oil exhibit good repellent efficacy against F. taiwana and significant slow-release effect, instead of adversely affecting the cell viability.

Fabrication and Characterisation of Titanium Dioxide (Tio2)/PVA Nanofibre Composites using Electrospinning

A study on the formation of titanium dioxide (TiO2)/ polyvinyl alcohol (PVA) nanofibres has been investigated in the research work. In the study, the TiO2/PVA solutions were prepared at different concentrations ranging from 1wt% to 10wt%. The PVA solution without TiO2 was used as control sample in the study. Each solution was extruded using electrospinning at different voltages to form long and continuous nanofibres. The fibres were then characterised for morphological structures, fibre diameter and membrane area. The result shows that control sample of PVA nanofibres formed beads on the fibre surfaces. The addition of TiO2 in PVA was found to reduce the bead formation. The clumps of TiO2 nanoparticles were observed and were also confirmed with the EDX mapping. In addition, the electrospinning parameters affect the formation of TiO2/PVA nanofibers. At 15 kV, the resultant fibre diameter increases from 153 ± 23 nm to 191 ± 26 nm when the TiO2 concentration was further increased from 1wt% to 10wt%. The morphological structure of TiO2/PVA nanofibres varies depending on applied voltages and concentrations used. The membrane area of TiO2/PVA nanofibers is approximately 187 cm2 for 1wt% of TiO2. From the study, it shows that an optimalconcentration to produce TiO2/ PVA nanofibers is 10wt%. At 10wt%, no beads were observed on the fibre and the TiO2 nano-particles were uniformly distributed on the membrane surfaces.