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

► PNIPAM films containing GOD are chemically polymerized on electrode surface. ► The CV response of ferrocenecarboxylic acid at the film electrodes is sensitive to temperature, sulfate concentration, and addition of methanol. ► This property can be used to realize the triply switchable bioelectrocatalysis of glucose catalyzed by GOD. 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 SO42−- 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-, SO42−-, 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.