Construction of ultrasensitive label-free aptasensor for thrombin detection using palladium nanocones boosted electrochemiluminescence system

Abstract

Aptamer-based bioassay of biomarker has broad applications in clinical research and disease diagnosis. In this work, a label-free aptamer biosensor for ultrasensitive thrombin (TB) detection was constructed based on highly enhanced electrochemiluminescence (ECL) of functional palladium nanocones (Pd NCs) with tripropylamine (TPA) system. Herein, well-defined Pd NCs were initially functionalized by mercaptoethanol (MCH) as an ECL emitter and immobilized onto the glassy carbon electrode (GCE) initially grafted with amine-terminated polyamidoamine (PAMAM) via electro-oxidation reaction. Under optimal conditions, the ECL intensity of the Pd NCs/TPA system was about 2.5 times enhancement when compared to that of bare GCE. The ECL and cyclic voltammetry (CV) were synchronously employed to illustrate the enhanced ECL mechanism. By virtue of the linkage of the modified Pd NCs with specified TB aptamer (TBA) containing sulfydryl group, a label-free ECL detection platform was designed. After full coverage of the nonspecific sites with bovine serum albumin (BSA), an ECL biosensor for TB detection was constructed by taking the advantage of the steric hindrance effects, showing the wider linear range, lower detection limit of TB (even down to 6.76 fM), superb selectivity and stability. The current strategy provides a highly sensitive platform for detection of various biomolecules in bioanalysis.