Drug diffusion and binding in ionizable interpenetrating networks from poly(vinyl alcohol) and poly(acrylic acid)

Hydrogels of poly(vinyl alcohol) (PVA), poly(acrylic acid) (PAA), and their interpenetrating networks (IPNs) were prepared using glutaraldehyde and ethylene glycol dimethacrylate as crosslinking agents. The hydrogels were characterized by measuring their equilibrium polymer volume fraction, equilibrium swelling ratio, and mesh size. Drug and protein diffusion through these hydrogels were studied. Solutes studied included theophylline, vitamin B12 and myoglobin. The ratio of PVA and PAA in the IPNs was varied to study the effect of ionic polymer content on the polymer/drug interactions and on the drug diffusion rate. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to analyze the polymer/drug binding interactions. It was concluded that drug diffusion may be impeded by associated drug binding, especially in IPN hydrogels containing high amounts of PAA.