Polymer-Enzyme Films on Conductive Surfaces: from Surface Modification by a Dual-Stimuli-Sensitive Polymer to Design of Electrochemical Biosensors

An understanding of the effect of temperature on the adsorption of a pH- and thermoresponsive polymer─linear poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA)─onto conductive (gold/graphite) supports was achieved by a combination of two complementary techniques─flow-through quartz crystal microbalance with dissipation monitoring and atomic force microscopy. A subsequent uptake of an enzyme─glucose oxidase (GOx)─by the PDMAEMA films was examined using the same techniques. The temperature was demonstrated to be an important factor, which determines specific features of the modification of the conductive surfaces by the polymer and, accordingly, the amount of the enzyme that can be taken up by the PDMAEMA adlayer. To highlight an application value of the polymer-enzyme films, an amperometric glucose biosensor was designed, wherein the PDMAEMA film was deposited at different temperature conditions on a mediator-modified (MnO₂) screen-printed electrode (SPE). Being rather simple to make, the SPE/MnO₂/PDMAEMA/GOx constructs exhibit remarkable performance toward β-d-glucose quantification. Depending on the temperature of the PDMAEMA adsorption (25 or 40 °C), they show a high sensitivity (47 or 68 μA/(mM × cm²), respectively), a limit of detection in a submicromolar range (0.3 or 0.2 μM, respectively, at a signal-to-noise ratio (S/N) of 3), and a linearity in a range of 3 orders of magnitude (up to 300 μM). Besides, the SPE/MnO₂/PDMAEMA/GOx constructs demonstrate excellently stable enzymatic responses over manifold repeated measurements.