Label-free electrochemiluminescence aptasensor using Ru(bpy)32+ functionalized dopamine-melanin colloidal nanospheres and gold nanoparticles as signal-amplifying tags

Abstract A novel label-free electrochemiluminescence (ECL) aptasensor for sensitive and selective detection of thrombin was constructed using Ru(bpy) 3 2+ functionalized dopamine-melanin colloidal nanospheres (Dpa-melanin CNSs) and gold nanoparticles (AuNPs) as signal-amplifying tags. Dpa-melanin CNSs were synthesized by a simple chemical route. A large amount of Ru(bpy) 3 2+ was coated over the Dpa-melanin CNSs with large surface area using Nafion as a bridge to form the Ru(bpy) 3 2+ /Nafion/Dpa-melanin CNSs composite which was considered as a sensing platform. AuNPs were introduced to the platform for immobilization of aptamer and further amplification of signal. A label-free ECL aptasensor for thrombin detection was subsequently fabricated by assembling aptamer on AuNPs/Ru(bpy) 3 2+ /Nafion/Dpa-melanin CNSs modified electrode. Greatly enhanced sensitivity is achieved based on the dual signal amplification strategy. The high sensitive detection of thrombin could be realized and the detection limit of thrombin was down to 2.2 × 10 −13  M with a linear range from 1.0 × 10 −12 to 1.0 × 10 −9  M. The aptasensor was applied to the thrombin analysis of human plasma samples with recoveries of 86.0-97.7%.