Significantly improving the performance of self-powered biosensor by effectively combining with high-energy enzyme biofuel cells, N-doped graphene, and ultrathin hollow carbon shell

Abstract

On-site monitoring of l-cysteine (L-Cys) has great significance for clinical diagnosis. In this study, a portable, fast, and ultrasensitive self-powered biosensor based on the single-chamber glucose/air enzymatic biofuel cell (EBFC) is proposed for the detection of l-Cys. Gold nanoparticles (AuNPs) and ultrathin hollow carbon shells (UHCS) were prepared and used as the biocathode and bioanode base material of EBFC, respectively. The electron transfer rate of the enzyme and electrode was enhanced by using a carbon paper (CP) electrode base modified with UHCS/AuNPs. DNA1/UHCS/AuNPs/CP was used as the biocathode of the self-powered biosensor where DNA1 was fixed on the electrode surface by Au–N bond, and the bioanode was obtained by loading laccase on the polydopamine film-modified substrate electrode. AuNP-decorated N-doped graphene was synthesized and immobilized with DNA2 modified with glucose oxidase (GOD) to form a bioconjugate. Due to the Ag+-mediated hybridization of DNA1 and DNA2, a C–Ag+–C complex will be formed, and the bioconjugate could bind to the bioanode. The reaction of glucose catalyzed by GOD can release electrons and result in the significant open-circuit voltage (EOCV) of the biosensor due to the reduction reaction occurred on the cathode. . When l-Cys is present, l-Cys forms an insoluble thiolate with Ag+. As a result, the conjugates are detached from the electrode surface, and the signal is significantly reduced. l-Cys can be detected in an expanded linear range of 0.01–5 μM with a detection limit of 2.20 nM. The developed self-powered biosensor exhibits high selectivity, outstanding reproducibility, and excellent stability for the detection of l-Cys in human urine samples. It can be used as a potential prototype for implantable and point-of-care diagnostic devices.