Interesting Correlation Between Structure, Physicomechanical, Swelling and Sustained Transdermal Release Behavior of Diltiazem Hydrochloride in Various Poly(vinyl alcohol) Hydrogel Membranes Tridib Bhunia, 1 Manas Bhowmik, 2 Dipankar Chattopadhyay, 1 Abhijit Bandyopadhyay 1 1 Department of Polymer Science and Technology, University of Calcutta, Calcutta 700009, India 2 Department of Pharmaceutical Technology, Jadavpur University, Calcutta 700032, India Received 31 July 2010; accepted 13 April 2011 DOI 10.1002/app.34678 Published online 5 January 2012 in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: Interesting correlation between physicome- chanical and in vitro release behavior of diltiazem hydro- chloride 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 molec- ular weight PVA membranes have shown acceptable release of diltiazem hydrochloride when compared with thermally treated high molecular weight PVA mem- brane. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 124: E177– E189, 2012 Key words: poly(vinyl alcohol); hydrogel; freeze-thaw; in vitro; controlled release INTRODUCTION Poly(vinyl alcohol) (PVA) is a versatile polymer with lot of commercial value. 1 It has different grades sub- ject to different degree of hydrolysis from its precur- sor poly(vinyl acetate). 1 Extent of water absorption controls its crystallinity—higher water absorption generally leads to lower crystallinity and vice versa. 2 PVA is an excellent biocompatible and biodegrad- able polymer, 3 but its degree varies with the extent of hydrolysis and molecular weight. It forms strong hydrogel owing to extensive intramolecular and intermolecular hydrogen bonding with water. 4,5 The water uptake property of PVA, that is, its swelling behavior can be modulated either by passive net- working, that is, physically by annealing or chemical crosslinking using bifunctional crosslinkers, such as dianhydrides, 6 diisocyanates, 7 glutaraldehydes, 8,9 and so on, and boric acid, 10 which simultaneously reacts with multiple hydroxyl groups of PVA. Net- work density, in both cases, governs the swelling behavior. Recently, hydrogels have been extensively studied as potential agent in numerous biomedical applications such as biosensors, bioreactors, biosepa- rators, tissue engineering, and drug delivery. 11–13 Some of the mostly studied polymers, include PVA, poly(acrylic acid), poly(methacrylic acid), poly (hydroxyethyl methacrylate), poly(acrylamide)-their blends/derivatives, and so on, and cellulosics (methyl cellulose, ethyl cellulose, etc.). Potency of polymer hydrogels in advanced/con- trolled drug delivery application has been widely explored off late since conventional drug therapy (oral and intravenous) has a serious drawback of short therapeutic time forcing into multiple adminis- trations and drug overload problems in the body. The only advantage of conventional therapy is its low cost. Polymer hydrogel membranes/films en- capsulate biomolecules such as water soluble pro- teins and drugs on account of their high viscosity and attractive interaction with the matrix and pro- vide a resistive pathway against its outward diffu- sion. Thus, the elution of drug/biomolecules from hydrogels could be controlled, which finally leads to wider therapeutic window. Kim et al., 14 in a recent literature, has demonstrated time profile of the actions of differently administered drugs in the body. They have also provided a list of various poly- meric gels explored in vivo and in vitro for controlled release studies. 14 In vivo application is more targeted organ specific and is termed as ‘‘targeted drug deliv- ery/on-site release’’ as these gels attains three- Correspondence to: A. Bandyopadhyay (abpoly@caluniv. ac.in). Contract grant sponsor: Council of Scientific and Industrial Research, Govt. of India. Journal of Applied Polymer Science, Vol. 124, E177–E189 (2012) V C 2012 Wiley Periodicals, Inc.