Triply switchable bioelectrocatalysis based on poly(N-isopropylacrylamide) hydrogel films with immobilized glucose oxidase

Poly( N -isopropylacrylamide) (PNIPAM) hydrogel films containing glucose oxidase (GOD), designated as PNIPAM-GOD, were synthesized on the surface of pyrolytic graphite (PG) electrodes through radical cross-linking polymerization method. Cyclic voltammetric (CV) response of ferrocenecarboxylic acid (Fc(COOH)) at PNIPAM-GOD film electrodes was very sensitive to the environmental temperature, sulfate concentration, and addition of methanol solvent. For example, at 25   °C, Fc(COOH) exhibited a quasi-reversible CV peak pair with large peak currents in pH 7.0 aqueous solutions containing no sulfate for the films; while at 37   °C, the CV response was greatly suppressed. By switching the film electrodes in solutions between 25 and 37   °C, the CV peak currents of Fc(COOH) cycled between a quite large value and a very small one, showing the reversible thermo-sensitive switching property between the on and off states. Similarly, the reversible SO 4 2− - and methanol-sensitive on–off behavior of the films toward the probe was also observed. This triply responsive property could be used to realize the thermo-, SO 4 2− -, and methanol-controlled electrochemical oxidation of glucose catalyzed by GOD immobilized in the films and mediated by Fc(COOH) in solution. This “smart” interface may establish a foundation for fabricating a novel type of multi-controllable biosensors based on bioelectrocatalysis.