Electrically Controlled Release of Benzoic Acid from Poly(3,4-ethylenedioxythiophene)/Alginate Matrix: Effect of Conductive Poly(3,4-ethylenedioxythiophene) Morphology

A drug-loaded conductive polymer/hydrogel blend, benzoic acid-loaded poly(3,4-ethylenedioxythiophene/alginate (BA-loaded PEDOT/Alg) hydrogel, was used as a carrier/matrix for an electrical stimuli transdermal drug delivery system (TDDS). The effects of cross-linking ratio, PEDOT particle size, and electric field strength on the release mechanism and the diffusion coefficient (D) of BA were examined by using a modified Franz-diffusion cell. The diffusion scaling exponent value of BA is close to 0.5 which refers to the diffusion controlled mechanism, or the Fickian diffusion as the BA release mechanism. The D increased when there was a decrease in the cross-linking ratio due to the mesh size-hindering effect. When increasing electric field strength, the D of BA-loaded PEDOT/Alg hydrogel increased because the cathode-BA(-) electrorepulsion, electroinduced alginate expansion, and PEDOT electroneutralization simultaneously occurred. The highest D belonged to a blend with the smallest PEDOT particle and highest electrical conductivity. The D of BA was a function of the matrix mesh size except when drug size/mesh size was lower than 2.38 x 10(-3), where D of BA became mesh size independent as the matrix mesh size was extremely large. Thus, the fabricated conductive polymer hydrogel blends have a great potential to be used in TDDS under electrical stimulation.