Polythiophene/carrageenan hydrogel as drug release matrix under electric field

Abstract

Development of the conductive polymer-hydrogel blend between polythiophene (PTh) doped with acetylsalicylic acid (ASA) and a carrageenan hydrogel for the transdermal drug delivery was investigated, in which the characteristic releases depend on the electric field applied. The carrageenan and their blend films were prepared by the solution casting using acetylsalicylic acid as the model drug and doping agent for PTh and MgCl₂, CaCl₂, and BaCl₂ as the crosslinking agents. The average molecular weight between crosslinks, the crosslinking density, and the mesh size of the carrageenan hydrogels were determined using the equilibrium swelling theory, as well as by scanning electron microscopy. The release mechanism and diffusion coefficients of blend PTh/carrageenan hydrogels and the non-blened ones were determined by using a modified Franz-Diffusion cell in an MES buffer solution, pH 5.5, at 37 ºC, for a period of 48 h in order to investigate the effects of the crosslinking ratio, the type of crosslinking agent and the electric field strength. The amounts of drug released were analyzed by UV-Visible spectrophotometry. The diffusion coefficient of drug was calculated through the Higuchi equation. The diffusion coefficient decreases with increasing the crosslinking ratio and decreasing the crosslinking ion size with and without the conductive polymer. The diffusion coefficients are greater at the applied electric field of 2.0 V by an order of magnitude relative to those without electric field. Moreover, the diffusion coefficients with the conductive polymer are better than without the conductive polymer.