A new signal amplification strategy using semicarbazide as co-reaction accelerator for highly sensitive electrochemiluminescent aptasensor construction

• 1、College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715

Abstract：A sensitive electrochemiluminescent (ECL) aptasensor was first proposed based on the employment of a kind of co-reaction accelerator to promote the co-reaction rate of peroxydisulfate and CdTe quantum dots (CdTe QDs) for boosting signal amplification. The co-reaction accelerator is a species that, upon oxidation or reduction, improves the co-reaction rate of luminophore and corectant to significantly enhance the ECL signal. In this work, semicarbazide (Sem) acted as the co-reaction accelerator. Primarily, the co-reaction accelerator of Sem functionalized Au nanoparticles (AuNPs) /gold nanocages (AuNCs) nanocomposite was prepared and labeled to detection aptamer of thrombin (TBA 2), acting ECL signal amplification tags. Herein, the Sem could serve as crosslinking agent to assemble AuNPs and AuNCs via Au-N bond, thus obtained the multifunctional nanomaterial of AuNPs-Sem-AuNCs. More importantly, it could act as co-reaction accelerator to facilitate the co-reaction rate of peroxydisulfate and CdTe QDs for realizing the signal amplification. Meanwhile, CdTe QDs composite film was constructed by a layer-by-layer (LBL) assembly of L-Cysteine functionalized C60 nanoparticles, poly (diallyldimethyl ammonium chloride) (PDDA), CdTe QDs and chitosan (CS). Then the resultant electrode was electrochemically deposited Au nanopaticles (Dp AuNPs) as a nano-matrix for subsequently immobilization of thiol-terminated thrombin capture aptamer (TBA 1). After TBA 1, TB, and TBA 2 signal labels forming a sandwich-type structure, a considerably enhanced ECL signal was obtained in the testing buffer of peroxydisulfate solution, for that Sem of the TBA 2 signal labels could catalyze the reduction of peroxydisulfate to produce the more strong oxidant mediator , which further boosted the production of excited states of QDs by using the strong oxidant mediator as the coreactant of QDs. The signal amplification ECL method, utilizing Sem as the co-reaction accelerator, was employed to quantify the concentration of TB with a detection limit of 0.03 fM.

Keywords： Electrochemiluminescence aptasensor Co-reaction accelerator Signal amplification Peroxydisulfate Semicarbazide CdTe quantum dot