Self-cleaning sensors based on thermoresponsive polymeric film modified screen-printed platinum electrodes

Electrochemical sensors have progressively become important tools for monitoring the concentration of complex substances in biological media. However, surface fouling and biological contamination from bio-colloids have not been effectively resolved. In this study, a self-cleaning electrochemical sensor was constructed where a thermoresponsive outer polymer layer was equipped to repel the absorbent proteins. Enhanced hydrophilic P(NIPAAm-co-NVP) copolymers bearing N-isopropylacrylamide (NIPAAm) and N-vinyl pyrrolidone (NVP) were synthesized by free radical polymerization, and the resulting thermoresponsive polymeric films were drop coated on screen-printed platinum electrodes (SPPEs) followed by thermal annealing. Grafting density, surface wettability, surface microstructure, amperometric response, electrochemical active surface area (EAS) and other performances, were evaluated for the modified SPPEs. Self-cleaning behavior after albumin adsorption was assessed by cyclic voltammetry (CV) and scanning electron microscopy (SEM) using various set temperatures respectively. The results showed the lower critical solution temperature (LCST) varied from 25 °C to 40 °C for P(NIPAAm-co-NVP) copolymers with the NVP content ranging from 0 to 47.62%. It indicated that NVP enhanced film hydrophilicity and could raise the LCST to above physiological data. The thermosensitivity, stability and repeatability of the modified sensors was proved to be well, and the unchanged selectivity was consistent with bare platinum electrodes. The copolymer film modified SPPEs showed the decreased and temperature-dependent EAS compared with bare SPPEs. It was concluded that films without NVP or with low NVP content resisted protein adsorption over lower temperatures, whilst with higher NVP content outstanding self-cleaning ability was also seen at physiological temperature. This opens the way to realize smart thermally addressable sensors able to solve the existing problem of biological surface contamination in sensor systems, and provides a strong model basis and technical capability for achieving novel, low drift electrochemical sensors.