Biochemical reaction-regulated electrocatalytic bipolar electrochemiluminescence platform with immobilization-free...

A biochemical reaction-regulated electrocatalysis strategy for quantitative cholesterol detection using platinum nanoparticle-functionalized indium tin oxide electrodes for electrochemiluminescence. In this system, cholesterol is oxidized by cholesterol oxidase to generate H₂O₂ in situ, which serves as an endogenous electroactive species and undergoes reduction at the BPE cathode. According to the charge balance principle, the cathodic reaction drives the anodic oxidation of the Ru(bpy)₃²⁺/TPrA system, generating an ECL signal that correlates quantitatively with cholesterol concentration. PtNPs at the BPE cathode enhance the electrocatalytic reduction of H₂O₂ and accelerate interfacial electron transfer, leading to an amplified anodic ECL response. Under optimized conditions, the platform exhibits a linear range of 0.1-10 mM with an extrapolated detection limit of 98.4 µM. The proposed sensing strategy was successfully applied to cholesterol detection in human serum samples, demonstrating good accuracy and anti-interference capability. Notably, the ChOx-catalyzed oxidation of cholesterol proceeds homogeneously in the sensing solution, while no enzyme-immobilization step is required during sensor preparation. In addition, no externally added electroactive species are required in the sensing cell, while the Ru(bpy)₃²⁺/TPrA ECL system is confined to the reporting cell. This sensing/reporting separation effectively minimizes cross-interference.