Electroactive and Thermoresponsive Hybrid Microgel on a Gold Surface for Electrochemically Controlled Release of Active Substance

In this study, we present a thermoresponsive and electroactive hybrid microgel immobilized on an electrode surface, designed as a platform for electrochemically induced release of positively charged model substances. The microgel was synthesized using <i>N</i>-isopropylacrylamide (NIPA) copolymerized with sodium acrylate (AcNa) and cross-linked with a cystine derivative (BISS). Poly(3,4-ethylenedioxythiophene) (PEDOT) spheres were incorporated within the microgel matrix, enhancing its electroactive properties. The structural and functional properties of the microgel were characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM) coupled with energy dispersive spectroscopy (EDS), and cyclic voltammetry. The microgel was anchored onto the gold electrode surface through a chemisorption process facilitated by disulfide bridges present in the cross-linking agent. The adsorption process was monitored using quartz crystal microbalance with energy dissipation (QCM-D). Subsequently, a positively charged model compound, crystal violet, was incorporated into the microgel structure through electrostatic interactions with carboxyl groups. The electrochemically induced release of the dye molecules was then investigated. Upon applying an electrochemical potential to the microgel-coated electrode, oxidation of PEDOT groups generated positive charges. This, in turn, disrupted the electrostatic interactions between the microgel network and the dye molecules, facilitating their release into the surrounding medium. The release process was quantitatively monitored using UV-Vis spectrophotometry. This system demonstrates potential as a promising drug delivery platform for use in implantable biomedical devices.