A New Policy To Develop The Disposable Label-free Immunosensor With Electrochemiluminescent Probing

In this paper, a novel designed label-free electrochemiluminescent(ECL) immunosensor using luminol as luminescent probe was fabricated. Immunoassay, based on the specific recognition between the antigen and antibody, is believable to be a high selective detection method for those bioactive molecules.A disposable glass sheet coated with indium tin oxide(ITO) was used as the substrate after functionalized with 3-aminopropyltrimethoxysilane(APTMS) to densely and homogeneously attach the Au NPs on its surfaces. These gold nano-particles coated on the substrate not only acted to load the antibody, but also improved the ECL intensity of luminol. This strategy for immunosensor construction is easier, faster, cheaper and also requires no expensive apparatus. Compared with those reported label-free immunosensors and immunoassays with the signaling techniques such as amperometry, electrochemical impedance spectroscopy(EIS), surface plasmon resonance(SPR), quartz crystal microbalance(QCM) and so on, the most outstanding merits of this new s ensor include the simple procedure for sensor preparation, high sensitivity, low cost and facile application.For validation of practicability of this new strategy, with methamphetamine(MA, also known as “Ice”) as target model, has been detected. Methamp hetamine is one of the most consumed illicit drugs with the toxicity for the mammalian brain to induce the neurotoxicity especially the long-lasting damage in the central dopaminergic pathway. The MA-antibody was immobilized onto the surface of previously mentioned substrate to build an MA sensor.The preparation process of the immunosensor was monitored by electrochemical impedance spectroscopy(EIS) and atomic force microscopy(AFM). The ECL intensity on resulted sensor decreased proportional to the conc entration of MA during the direct immunoreaction in a wide linear range of 2 ng m L-1- 500 ng m L-1. The limit of detection was 0.3 ng m L-1 in phosphate buffer saline. This proposed method is sensitive, specific, stable and reliable. It has been successful ly applied to detect the MA in spiked human serums.