A highly sensitive and stable glucose biosensor using thymine-based polycations into laponite hydrogel films

Abstract

A series of glucose bioelectrodes were prepared by glucose oxidase (GOx) immobilization into laponite hydrogel films containing DNA bioinspired polycations made of vinylbenzyl thymine (VBT) and vinylbenzyl triethylammonium chloride (VBA) with general formulae [ ( VBT ) m ( VBA ) n ] ≈ 25 n + with m=0, 1 and n=2, 4, 8, deposited onto glassy carbon electrode. The bioelectrodes were characterized by chronoamperometry, cyclic voltammetry and electrochemical impedance spectroscopy. Results indicated that the electrochemical properties of the laponite hydrogel films were largely improved by the incorporation of thymine-based polycations, being proportional to the positive charge density of the polycation molecule. After incorporation of glucose oxidase, the sensitivity of the bioelectrode to glucose increased with the positive charge density of the polycation. Additionally, the presence of the vinylbenzyl thymine moiety played a role in the long-term stability and reproducibility of the bioelectrode signal. As a consequence, the [ ( VBT ) ( VBA ) 8 ] ≈ 25 8 + was the most appropriate polycation for bioelectrode preparation and glucose sensing, with a specific sensitivity of se=176 mA mmol−1 L cm−2 U−1, almost two-order of magnitude larger than other laponite immobilized GOx bioelectrodes reported elsewhere. These features were confirmed by testing the bioelectrode for a selective determination of glucose in powder milk and blood serum samples without interference of either ascorbic or uric acids under the experimental conditions. The present study demonstrates the suitability of DNA bioinspired water-soluble polycations [ ( VBT ) m ( VBA ) n ] ≈ 25 n + for enzyme immobilization like GOx into laponite hydrogels, and the preparation of highly sensitive and stable bioelectrodes on glassy carbon surface.