AuNPs/rGO-enhanced molecularly imprinted field-effect transistor sensor for highly selective detection of lactic acid in sweat

Abstract

Lactic acid (LA) represents a critical metabolic biomarker for early disease diagnosis, monitoring disease progression and therapeutic assessment, necessitating the development of sensitive and reliable detection methods. Herein, a label-free field-effect transistor (FET) sensor incorporating a molecularly imprinted polymer (MIP) is developed for highly sensitive LA detection. The sensing platform is constructed through template-assisted electropolymerization of o-phenylenediamine (o-PD) on gold nanoparticle-decorated reduced graphene oxide (AuNPs/rGO), where graphene oxide (GO) is electrochemically reduced to form structurally stable rGO. The synergistic integration of the catalytic activity of AuNPs, exceptional surface area of rGO, and the specific recognition capability of MIP significantly enhances the sensitivity and stability of the sensor. Upon LA binding to the MIP recognition sites through hydrogen bonding and steric complementarity, these interactions trigger charge redistribution in the FET channel, modulating the carrier concentration and mobility, consequently causing measurable shifts in the transfer characteristics. The electrical signal changes directly correlate with LA concentration, enabling quantitative detection. The optimized sensor demonstrates excellent analytical performance with a wide linear detection range spanning from 10 pM to 1 mM and a low detection limit of 3.33 pM. Furthermore, the platform exhibits superior selective and anti-interference capability against common sweat interferents including glucose, urea, and citric acid. The MIP-integrated FET sensor offers a cost-effective, highly sensitive solution for LA detection with significant potential for in vitro disease diagnosis.