Electrochemically Induced Formation of Surface‐Attached Temperature‐Responsive Hydrogels. Amperometric Glucose Sensors with Tunable Sensor Characteristics

Abstract

Abstract Employing thermally responsive hydrogels, the design of an amperometric glucose sensor is proposed. The properties of the biosensor can be modulated upon changing the temperature. Homo‐ and copolymers of N ‐isopropylacrylamide (NIPAm) and oligo(ethylene glycol) methacrylate (OEGMA) were prepared by electrochemically induced polymerization thus yielding surface‐attached hydrogels. The growth of the films as well as the change in the film thickness in dependence from the temperature were investigated by means of an electrochemical quartz crystal microbalance (EQCM). The layer thickness in the dry state ranged from 20 to 120 nm. The lower critical solution temperature (LCST) of the hydrogel increases with increasing content of the more hydrophilic OEGMA. Hence, the swelling in aqueous electrolyte is composition dependent and can be adjusted by selecting a specific NIPAm to OEGMA ratio. All homo‐ and copolymer films showed good biocompatibility and no fouling could be observed during exposing the surfaces to human serum albumin. For amperometric glucose detection, glucose oxidase was entrapped in the films during electrochemically‐induced polymerization. Both the apparent Michaelis constant ( K $\rm{{_{M}^{app}})}$ and the apparent maximum current ( i $\rm{{_{max}^{app}})}$ as determined by amperometry could be adjusted both by the film composition as well as the operation temperature.