Alginate-graft-polyacrylic acid electro-responsive hydrogels: Impact of the conducting polymer and application as hydrogen peroxide sensor

Abstract

Aiming to advance in the field of soft bioelectronics interfaces, hydrogels obtained from synthetic polyacrilic acid (PAA) grafted to alginate (Alg), Alg-g-PAA, have been rendered electro-responsive by incorporating semi-interpenetrated conducting polymer (CP) chains. The three CPs considered, poly(hydroxymethyl-3,4-ethylenedioxythiophene) (PHMeEDOT), polypyrrole (PPy) and polyaniline (PAni), were incorporated either after the formation of the Alg-g-PAA hydrogel (PHMeEDOT and PAni), or in situ during its preparation (PPy). After chemical and physical characterization, the electrochemical response and cytocompatibility of Alg-g-PAA/PHMeEDOT, Alg-g-PAA/PPy and Alg-g-PAA/PAni hydrogels were evaluated by cyclic voltammetry and the MTT assay, respectively. While the transport of ions in Alg-g-PAA produces some electrochemical activity, hydrogels semi-interpenetrated with CPs exhibited a significant enhancement of the electrochemical response on account of the electronic contribution of the CP. The conducting hydrogel with the highest cytocompatibility was found to be Alg-g-PAA/PHMeEDOT, the PPy and PAni semi-intercalated hydrogels displayed some cytotoxicity due to unreacted reagents employed for the preparation of the CP component (i.e. monomer and/or oxidizing agent). Finally, the potential application of the semi-interpenetrated conducting hydrogels as biosensors for the electrochemical detection of hydrogen peroxide was explored. Alg-g-PAA/PHMeEDOT, which was more sensitive to the presence of hydrogen peroxide than the other two CP-containing hydrogels, exhibited a sensitivity of 71.9 mA/(cm2·mM) and a detection limit of 0.9 mM.