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ABSTRACT Hybrid membranes based on poly(vinyl alcohol) (PVA) of widely different molecular weights and ex situ nanosilica were synthesized and characterized as transdermal delivery device for Diltiazem hydrochloride. Investigations showed that change in PVA molecular weight strongly influenced physico-mechanicals of the hybrids especially at low nanosilica content than at higher levels. As for example at 1 wt %, low molecular weight PVA induced finer dispersion of silica nanoparticles resulting into higher dry state crystallinity and mechanical strength but slightly lower biocompatibility as compared to high molecular weight PVA. Those variations in physico-mechanicals finally affected Diltiazem retention and its elution from those membranes under physiological conditions. Low molecular weight PVA produced highest drug retention as well as slowest yet steady release than both high molecular weight PVA and neat PVA membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2076-2086, 2013 [ABSTRACT FROM AUTHOR]

Interesting correlation between physicomechanical and in vitro release behavior of diltiazem hydrochloride has been obtained in physically treated poly(vinyl alcohol) (PVA) membranes of widely different molecular weights. Physical treatment could not raise crystallinity in dry state, but some of them show significant postswelled crystallinity and achieves elastomeric character. They also retain lot of equilibrium water, ideally suited for drug-impregnated transdermal patches. In effect, low molecular weight PVA and dimethyl sulfoxide-modified high molecular weight PVA membranes have shown acceptable release of diltiazem hydrochloride when compared with thermally treated high molecular weight PVA membrane. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Change in poly (vinyl alcohol) (PVA) molecular weight has been found to affect nanosilica phase morphology in PVA-ex-situ silica aqueous gel which in turn influences shear viscometric parameters such as near-zero shear viscosity, pseudoplastic index, thixotropic index and net viscosity drop at various levels of nanosilica contents. About 25 °C rise in temperature does not produce any serious changes in these parameters from that studied at room temperature. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]