Tannic Acid-Reduced Graphene Oxide Deposited with Pt Nanoparticles for Switchable Bioelectronics and Biosensors Based on Direct Electrochemistry

In this study, we reported a novel biosensor based on direct electrochemistry of glucose oxidase (GOx) on a tannic acid-reduced graphene oxide nanocomposite modified glassy carbon electrode deposited with Pt nanoparticles. Tannic acid (TA) was utilized for the simultaneous green reduction of Pt4+ and graphene oxide (GO), along with modifying the reduced GO for the GOx immobilization, thus constructing a switchable surface with pH and temperature alterations. Upon the electrochemically oxidation of TA to quinone, enhanced electron transfer was obtained, and a third generation biosensor was fabricated using pi-pi it interaction between GO and TA and Schiff-base assisted hydrogen bonds between GOx and TA interactions. The redox peaks were observed at a formal potential of -0.462 V with a peak separation (Delta E-p) of 56 mV, which reveals the fast electron transfer. The linear response to glucose oxidation was in the range of 2-10 mM with a limit of detection of 1.21 mu M and a sensitivity of 27.51 mu A mM(-1) cm(-2). Upon the deposition of poly(N-isopropylacrylamide) (PNIPAAm) onto the constructed biosensor via hydrogen bonds, an on off biosensor was fabricated with zipperlike interfacial properties upon the formation of the shrunken and compact globule PNIPAAm structure and varying surface charge. Therefore, this study confirmed the versatile aspects of natural TA without using complicated methods.