(A) label-free and washing-free method to detect biothiols on personal glucose meter utilizing glucose oxidase-mimicking activity of gold nanoparticles

Abstract

Herein, we developed a label-free and washing-free method to detect the biological thiol (biothiol) on the personal glucose meter (PGM) utilizing gold nanoparticles (AuNPs) possessing intrinsic glucose oxidase (GOx)-mimicking activity. In principle, the biothiols bind to the surface of AuNPs through the formation of gold-sulfur (Au-S) bond and thus inhibit the direct access of glucose onto AuNP surface. As a result, the efficiency for AuNP-catalyzed glucose oxidation reaction is reduced, leading to the maintenance of initial high glucose level that can be simply measured by PGM. With this strategy, various biothiols such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) were successfully determined down to 0.116, 0.059, and 0.133 $\mu$M, respectively, with high selectivity against other amino acids without thiol groups. We also demonstrated practical applicability of this sensing strategy by reliably detecting the biothiols in the human serum.