Swelling deswelling studies after freeze–thaw treatment of nanosilica reinforced poly (vinyl alcohol)-based organic–inorganic hybrid hydrogel
01 Aug 2011-International Journal of Nanoscience (World Scientific Publishing Company)-Vol. 10, pp 1087-1090
TL;DR: Aqueous nanosilica sol (particle size range: 9−13 nm, pH: 9.0) was added at various low concentration range (0.5−2 wt.%) to prevent any silica aggregation due to change in pH.
Abstract: Aqueous nanosilica sol (particle size range: 9–13 nm, pH: 9.0) was added at various low concentration range (0.5–2 wt.%) into aqueous poly (vinyl alcohol) (PVA) of different molecular weight (98% hydrolyzed, 20 wt.%) (pH: 5.0) at room temperature under constant stirring to synthesize organic-inorganic hybrid hydrogels in presence of sodium lauryl sulphate as a silica dispersant. Buffer tablets were added to arrest the pH at 9.0 (to prevent any silica aggregation due to change in pH). The resultant hybrids were cast on Teflon sheets and dried in an oven at 50°C to drive out all the unbound water. Those films were then subjected to freese-thaw treatment continuously for 5 h. The freese-thawed films appeared opaque. The swelling-de swelling experiments with the hydrogels were carried out in distilled water at room temperature and consequently allowed to de-swell naturally. Those observations were correlated with the microstructures of the hybrid hydrogels.
TL;DR: The aim of this article is to present a concise review on the applications of hydrogels in the pharmaceutical field, hydrogel characterization and analysis of drug release from such devices.
Abstract: The availability of large molecular weight protein- and peptide-based drugs due to the recent advances in the field of molecular biology has given us new ways to treat a number of diseases. Synthetic hydrogels offer a possibly effective and convenient way to administer these compounds. Hydrogels are hydrophilic, three-dimensional networks, which are able to imbibe large amounts of water or biological fluids, and thus resemble, to a large extent, a biological tissue. They are insoluble due to the presence of chemical (tie-points, junctions) and/or physical crosslinks such as entanglements and crystallites. These materials can be synthesized to respond to a number of physiological stimuli present in the body, such as pH, ionic strength and temperature. The aim of this article is to present a concise review on the applications of hydrogels in the pharmaceutical field, hydrogel characterization and analysis of drug release from such devices.
TL;DR: The unique structure of cryogels, in combination with their osmotic, chemical and mechanical stability, makes them attractive matrices for chromatography of biological nanoparticles and the immobilization of biomolecules and cells.
Abstract: Cryogels are gel matrices that are formed in moderately frozen solutions of monomeric or polymeric precursors. Cryogels typically have interconnected macropores (or supermacropores), allowing unhindered diffusion of solutes of practically any size, as well as mass transport of nano- and even microparticles. The unique structure of cryogels, in combination with their osmotic, chemical and mechanical stability, makes them attractive matrices for chromatography of biological nanoparticles (plasmids, viruses, cell organelles) and even whole cells. Polymeric cryogels are efficient carriers for the immobilization of biomolecules and cells.
TL;DR: In this paper, the structure of physical polyvinyl alcohol (PVA) hydrogels prepared by subjecting a PVA/D2O solution (11% w/w PVA) to freeze (−22 °C)/thaw (+25 °C) cycles has been systematically investigated by X-ray powder diffraction technique as a function of the number of cycles and aging time.
Abstract: The structure of physical poly(vinyl alcohol) (PVA) hydrogels prepared by subjecting a PVA/D2O solution (11% w/w PVA) to freeze (−22 °C)/thaw (+25 °C) cycles has been systematically investigated by X-ray powder diffraction technique as a function of the number of cycles and aging time. The structural analysis has been extended to PVA “dried gels” and PVA hydrogels obtained by rehydrating the dried samples. The results of the present analysis confirm that highly stable PVA hydrogels, with a water uptake higher than 80%, may be obtained upon freeze/thaw cycles. The X-ray diffraction profiles of PVA hydrogels have been interpreted in terms of three components: “free water”, crystalline PVA aggregates, and swollen amorphous PVA. The degree of crystallinity and the size of the crystals increase with increasing the number of freeze/thaw cycles and the aging time. Our results support the hypothesis that PVA hydrogels have a porous structure, with pores mainly occupied by water. The porous walls consist of swoll...
TL;DR: A new type of soft contact lens was developed from the poly(vinyl alcohol) (PVA) hydrogel prepared by a low temperature crystallization technique using a water-dimethyl sulfoxide mixed solvent and showed no difference in corneal epithelium and cell arrangement in the corneals from the non-wearing eyes.
Abstract: A new type of soft contact lens was developed from the poly(vinyl alchol) (PVA) hydrogel prepared by a low temperature crystallization technique using a water-dimethyl sulfoxide mixed solvent. The PVA contact lens materials had a water content of 78% and a tensile strength of 50 kg/cm2, five times as strong as that of commercial poly(2-hydroxyethyl methacrylate) soft contact lens. The amount of proteins adsorbed to the PVA soft hydrogel material was half to one thirtieth of that of conventional soft contact lenses. Histological and scanning electron microscopic observation of rabbit eyes which had worn the PVA soft contact lens for 12 weeks showed no difference in corneal epithelium and cell arrangement in the corneal epithelium from the non-wearing eyes.
TL;DR: In this article, the organic-inorganic hybrid nanocomposites comprising poly(iminohexamethyleneiminoadipoyl), better known as Polyamide-6,6 (abbreviated henceforth as PA66), and silica (SiO2) were synthesized through sol-gel technique at ambient temperature.
Abstract: The organic–inorganic hybrid nanocomposites comprising of poly(iminohexamethyleneiminoadipoyl), better known as Polyamide-6,6 (abbreviated henceforth as PA66), and silica (SiO2) were synthesized through sol–gel technique at ambient temperature. The inorganic phase was generated in situ by hydrolysis–condensation of tetraethoxysilane (TEOS) in different concentrations, under acid catalysis, in presence of the organic phase, PA66, dissolved in formic acid. Infrared (IR) spectroscopy was used to monitor the microstructural evolution of the silica phase in the PA66 matrix. Wide angle X-ray scattering (WAXS) studies showed that the crystallinity in PA66 phase decreased with increasing silica content. Atomic force microscopy (AFM) of the nanocomposite films revealed the dispersion of SiO2 particle with dimensions of <100 nm in the form of network as well as linear structure. X-ray silicon mapping further confirmed the homogeneous dispersion of the silica phase in the bulk of the organic phase. The melting peak temperatures slightly decreased compared to neat PA66, while an improvement in thermal stability by about 20 °C was achieved with hybrid nanocomposite films, as indicated by thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) exhibited significant improvement in storage modulus (E′) for the hybrid nanocomposites over the control specimen. An increase in Young's modulus and tensile strength of the hybrid films was also observed with an increase in silica content, indicating significant reinforcement of the matrix in the presence of nanoparticles. Some properties of the in situ prepared PA66-silica nanocomposites were compared with those of conventional composites prepared using precipitated silica as the filler by solution casting from formic acid.