Electrogenerated chemiluminescence peptide-based biosensing method for cardiac troponin I using peptide-integrating Ru(bpy)3 2+-functionalized gold nanoparticles as nanoprobe

Abstract

A sensitive electrogenerated chemiluminescence peptide-based (ECL-PB) biosensing method for the determination of protein was developed by employing peptide-integrating Ru(bpy)3 2+(bpy = 2,2′-bipyridine)-functionalized gold nanoparticles (Ru(bpy)3 2+-AuNPs-peptide) as nanoprobe. Cardiac troponin I (cTnI), a reliable clinical biomarker for the detection of cardiac injury, was chosen as target protein, while a specific binding peptide (CFYSHSFHENWPS) was used as molecular recognition element. AuNPs were firstly functionalized with Ru(bpy)3 2+ through electrostatic interactions between citrate-capped AuNPs and Ru(bpy)3 2+ to form Ru(bpy)3 2+-AuNPs aggregates and then functionalized with peptide through Au-S bounds to form Ru(bpy)3 2+-AuNPs-peptide nanoprobe. AuNPs not only can capture numerous signal-generating molecules, resulting in high ECL intensity but also can capture a significant amount of the peptide, providing poly binding motif. The specific capture peptide was self-assembled on the surface of a gold electrode and then incubated with the target cTnI and Ru(bpy)3 2+-AuNPs-peptide successively. A sandwich-type peptide/cTnI/Ru(bpy)3 2+-AuNPs-peptide conjugate was formed on the surface of the electrode and an ECL signal was obtained in the presence of tri-n-propylamine. The novel biosensing method facilitates the sensitive detection of cTnI in the range from 3.0 × 10−12 g mL−1 to 7.0 × 10−11 g mL−1 with a low detection limit of 0.5 pg mL−1. This work provides a promising strategy for the determination of proteins with simplicity, high sensitivity, and selectivity.