Thin films based on poly(N,N-dimethylaminoethyl methacrylate) and glucose oxidase: formation, properties and application as biosensor coatings

Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) is a stimuli-sensitive (pH- and temperature-sensitive) polymer. Its macromolecules readily change hydrophilic–hydrophobic balance in response to external stimuli (temperature, pH, solvent composition). This feature makes PDMAEMA adaptive to surfaces of different nature and very promising for their functionalization. In particular, its tertiary amino groups, when protonated, enable the non-destructive binding of (bio)molecules bearing the opposite charge. Hence, PDMAEMA can be exploited for the surface modification and further electrostatic immobilization of (bio)molecules, thereby paving a way towards (bio)sensor coatings, which are in demand in medicine, biotechnology, ecology and related fields.

In this work, the formation and properties of polymer and polymer–enzyme coatings on model conductive surfaces (gold, graphite) were examined by means of quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). PDMAEMA was proven to form nano-sized, stable and rigid films if adsorbed in a non-charged state (pH 10). After being brought to a charged state (pH 7), PDMAEMA films were shown to bind significant amounts of glucose oxidase (GOx). The efficiency of surface modification and amount of the immobilized enzyme were demonstrated to increase with the temperature of the polymer adsorption, changing from 25 up to 40°C.

Next, an electrochemical polymer-enzyme biosensor system was fabricated via subsequent adsorption of PDMAEMA and GOx on screen-printed graphite-based electrodes (SPE). An amperometric assay of the obtained biosensor constructs exhibited remarkable performance (i.e., a submicromolar limit of detection, a wide linear range of 3 orders of magnitude) toward glucose quantification as well as a good operational stability of enzymatic responses.

The experimental results (QCM-D and AFM) were obtained with the use of the equipment purchased within the M.V. Lomonosov Moscow State University Program of Development.