Electrically controlled release of sulfosalicylic acid from crosslinked poly(vinyl alcohol) hydrogel

Electrically controlled drug delivery using poly(vinyl alcohol) (PVA) hydrogels as the matrix/carriers for a model drug was investigated. The drug-loaded PVA hydrogels were prepared by solution-casting using sulfosalicylic acid as the model drug and glutaraldehyde as the crosslinking agent. The average molecular weight between crosslinks, the crosslinking density, and the mesh size of the PVA hydrogels were determined from the equilibrium swelling theory as developed by Peppas and Merril, and the latter data were compared with those obtained from scanning electron microscopy. The release mechanisms and the diffusion coefficients of the hydrogels were studied using modified Franz-Diffusion cells in an acetate buffer with pH 5.5 and temperature 37 degrees C during a period of 48 h, in order to determine the effects of crosslinking ratio, electric field strength, and electrode polarity. The amounts of drug released were analyzed by UV-vis spectrophotometry. The amounts of drug released vary linearly with square root of time. The diffusion coefficients of drug-loaded PVA hydrogels decrease with increasing crosslink ratio. Moreover, the diffusion coefficients of the charged drug in the PVA hydrogels depend critically on the electric field strength between 0 and 5 V as well as on the electrode polarity. Thus, the release rate of sulfosalicylic acid can be altered and controlled precisely through electric field stimulation.