An ultrasensitive peroxydisulfate electrochemiluminescence immunosensor for Streptococcus suis serotype 2 based on l-cysteine combined with mimicking bi-enzyme synergetic catalysis to in situ generate coreactant

A novel signal amplification strategy of mimicking bi-enzyme synergetic catalysis to generate coreactant in situ was designed to fabricate an ultrasensitive peroxydisulfate electrochemiluminescence (ECL) immunosensor for detection of Streptococcus suis serotype 2 (SS2). It was the first time to detect SS2 by using ECL. Through the interaction between l-cysteine (l-cys) and hollow PtPd bimetal alloy nanoparticles (HPtPd) to form ((l-cys-HPtPd)n) nanocomposites, the loading amount of l-cys and HPtPd was greatly increased, which could greatly enhance the ECL signal of peroxydisulfate. At the same time, Glucose Oxidase (GOD), used to block nonspecific binding sites of (l-cys-HPtPd)n nanocomposites, could rapidly oxidize d-glucose in the detection solution into gluconic acid accompanying with the generation of H2O2, which was further catalyzed by HPtPd to generate O2. And O2, acted as the coreactant of peroxydisulfate, could greatly amplify the ECL signal. In the process, HPtPd could be regarded as mimicking enzyme, the effect of which was similar to horseradish peroxidase (HRP) in generating O2. With the several amplification factors of a sandwich-type structure we designed, a wide linear ranged from 0.0001 to 100 ng mL−1 was acquired with a relatively low detection limit of 33 fg mL−1 for SS2. The present work demonstrated that the novel strategy had the great advantages in sensitivity, selectivity and reproducibility which might hold a new promise for highly sensitive bioassays applied in clinical detection.

► It was the first time to detect SS2 by using ECL.
► The nanocomposites of (l-cys-HPtPd)n greatly enhanced the ECL signal.
► GOD and HPtPd were adopted as mimicking enzyme to in situ generate O2 for signal amplification.
► The strategy has the advantages of sensitivity, good selectivity and reproducibility.