A Polyvinyl Alcohol-Polyaniline Based Electro-Conductive Hydrogel for Controlled Stimuli-Actuable Release of Indomethacin

Electro-conductive hydrogels based on poly(vinyl alcohol), crosslinked with diethyl acetamidomalonate as the hydrogel component, were engineered using polyaniline as the inherently conductive component, and fabricated in the form of cylindrical devices to confer electro-actuable release of the model drug indomethacin. The hydrogels were characterized for their physicochemical and physicomechanical properties. Cyclic voltammetry was employed for electro-activity and conductivity analysis. Drug entrapment efficiency ranged from 65-70%. ON-OFF switchable drug release was obtained by periodically applying-removing-reapplying an electric potential ranging from 0.3-5.0 V for 60 seconds at hourly intervals and the cumulative drug release obtained ranged from 4.7-25.2% after four release cycles respectively. The electro-stimulated release of indomethacin was associated with the degree of crosslinking, the polymeric ratio and drug content. A Box-Behnken experimental design was constructed employing 1.2 V as the baseline potential difference. The devices demonstrated superior swellability and high diffusivity of indomethacin, in addition to high electrical conductivity with ON-OFF drug release kinetics via electrical switching. In order to investigate the electro-actuable release of indomethacin, molecular mechanics simulations using AMBER-force field were performed on systems containing water molecules and the poly(vinyl alcohol)-polyaniline composite under the influence of an external electric field. Various interaction energies were monitored to visualize the effect of the external electric field on the erosion of polyaniline from the co-polymeric matrix. This strategy allows the electro-conductive hydrogels to be suitably applied for controlled, local and electro-actuable drug release while sustaining a mild operating environment.