Tyramide signal amplification and enzyme biocatalytic precipitation on closed bipolar electrode: Toward highly sensitive electrochemiluminescence immunoassay

Jun-TaoCao^a,c, Li-Zhen Zhao^a, Yi-Zhuo Fu^a, Xiang-Mei Liu^a, Shu-Wei Ren^b, Yan-Ming Liu^a

College of Chemistry and Chemical Engineering, Institute for Conservation and Utilization of Agro-Bioresources in Dabie Mountains, Xinyang Normal University, Xinyang, 464000, China.

Abstract

A novel closed bipolar electrode-based electrochemiluminescence (BPE-ECL) imaging platform for visual detection of cardiac troponin I (cTnI) was constructed using tyramine signal amplification (TSA) strategy and enzyme-catalyzed precipitation techniques (BCP). In this platform, tyramine-HRP repeats formation and the BCP were executed on the cathodic pole in the presence of H2O2, which the ECL from Ru(bpy)₃²⁺/TPA system was used as signal reporter on the anodic pole. In the presence of cTnI, a large number of HRP from HRP-Au NPs-Ab compounds and tyramine-HRP repeats catalyze the formation of insoluble precipitation on the cathodic pole of the BPE, resulting in the decreased ECL from Ru(bpy₃²⁺/TPA system on the anodic pole. Thanks to the TSA and BCP on the cathodic pole of the BPE platform, the method for cTnI detection exhibits the detection limits of 5.0 × 10^-13 g/mL by a photomultiplier tube and 5.0 × 10^-12 g/mL by a charge-coupled device imaging. Furthermore, the content of cTnI in human serum samples was determined and the recovery was between 90.0 % and 112.0 %. This multiple signal amplification strategy provides new perspectives for the BPE-ECL imaging platform in the biochemical analysis of biomarkers with low abundance.

Keywords: Bipolar electrode, Electrochemiluminescence, Imaging immune analysis, Tyramine signal amplification, Biocatalytic precipitation, Cardiac troponin I.