Highly sensitive electrochemiluminescence biosensor for cholesterol detection based on AgNPs-BSA-MnO₂ nanosheets with superior biocompatibility and synergistic catalytic activity

Monitoring the level of cholesterol in blood serum is a critical approach for diseases surveillance. In this work, we reported on the successful construction of a new electrochemiluminescence (ECL) sensor for cholesterol detection by employing the Ag-(bovine serum albumin) BSA-MnO₂ nanosheets for cholesterol oxidase (ChOx) immobilization and catalytic amplification of ECL signal. The AgNPs-BSA-MnO₂ nanosheets were synthesized by using BSA as protective agent, which greatly facilitated the immobilization of ChOx due to the existing amino group donated by BSA. The structure and properties of the AgNPs-BSA-MnO₂ nanosheets were characterized by a series of techniques, including transmission electron microscope (TEM), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). Importantly, experiment results indicated that the synergistic effect of AgNPs with MnO₂ nanosheets could provide excellent catalytic ability towards ROSs generation and thus to efficiently amplify the ECL signal of luminol-H₂O₂ system. Under optimal conditions, the ECL intensity increased with the increasing cholesterol concentration in a dynamic range from 0.21 μM to 1667 μM with a limit of detection (LOD) of 0.07 μM (3σ).