Electrochemiluminescence Immunosensor Based On Nanocomposite Film Of Surface Modified And Assembled CdS Nanoparticles

Electrochemiluminescence (ECL) has great potential for protein detection with the merits of being specific, simple, fast. The ECL immunosensors are developed by the relationship of ECL intensity and immunoreaction. Many studies show that semiconductor nanoparticles (NPs) have ECL properties. The application of semiconductor nanocrystals to ECL biosensing has friendly biocompatibility and is used in neutral solution. In this paper, CdS NPs were prepared and their application in ECL immunosensor was discussed. We use K2S2O8 as co-reactant. CdS nanoparticles are surface modified and assembled to enhance the ECL signal.The major work consists of two parts:In the first part of this paper, the detection of CdS QDs film modified ECL electrochemiluminescence immunosensor by electrodepositionCdS QDs were modified by directly potentiostatic electrodeposition on the surface of gold electrode. The obtained electrode was characterized by Scanning electron microscope (SEM). The result showed the large cauliflower-like CdS QDs formed by the small particlesize presented symmetric distribution. Compared with the CdS NPs thin film, ca. 5 times enhanced ECL was obtained for the electrodepodited CdS thin filmmodified gold electrode. The prepared immunosensor was characted by ECL, and the reaction instance between the anti-MIgG immobilized on the electrode surface and MIgG and the incubation time were also investigated. Under the optimal condition: 800s for electrodeposition CdS QDs, pH=7.4, 0.1M potassium persulface solution(K2S2O8), the incubation time was 30min, the ECL of immunosensor showed it had a lower detection limit(ng/mL) with its concentrations ranging from 0.6 to 100ng/mL. This immunosensor possessed high sensitivity, and held many merits such as smple fabrication process, which might provide an effective candidate for ECL immunosensor.In the second part of this paper, the detection of CdS NPs film modified ECL electrochemiluminescence immunosensor by surface modifingCdS NPs was prepared by chemical reaction and it were treated by heating in the presence of ammonia(CdS-NH₃ NPs was obtained). The experimental result showed that the enhancement of ECL may be due to the changes in morphology and the surface electronic structure of CdS NCs upon heating in the presence of ammonia. And the onset of reduction potential shifted positively and the cathodic peak current at the heated-CdS/Au was enhanced compared with the CdS/Au and the electrodepodited CdS/Au. The the reaction between the anti-MIgG and MIgG fixed on the electrode surface and the incubation time were investigated by ECL. Under the optimal condition, the ECL of immunosensor showed it had sensitive response for MIgG and exhibited a wide liner range. In the rang of MIgG concentrations from 0.006 to 150ng/mL, there was a good linear response and with a detection limit of several pg/mL. In addition, the prepared immunosensor could be regenerated 3 times with 4.0M urea solution. This suggests that ammonia plays an important role in enhancing the ECL of CdS NCs. This approach would open new avenues to apply NPs ECL in immunoassays.