Engineering of CdTe/SiO2 nanocomposites: Enhanced signal amplification and biocompatibility for electrochemiluminescent immunoassay of alpha-fetoprotein.

Electrochemiluminescent (ECL) performance and cytotoxicity of CdTe quantum dots (QDs)-based nanocomposites and its possible application for ECL immunoassay were investigated. Two types of CdTe-based nanocomposites, i.e., SiO2-coated CdTe (CdTe@SiO2) and CdTe-functionalized SiO2 (SiO2@CdTe), were synthesized and comprehensively compared in regarding of the cytotoxicity and ECL performance. The in vitro cytotoxicity of SiO2@CdTe and CdTe@SiO2 nanoparticles was assessed in L02 cells using standard CCK-8 assay, and their ECL performance was investigated by constructing sandwiched immunosensor using SiO2@CdTe and CdTe@SiO2 as tags for the labelled antibody, respectively. The results showed that CdTe@SiO2 exhibited much lower cytotoxicity and a higher ECL intensity than SiO2@CdTe. Taking the analysis of alpha-fetoprotein (AFP) as an example, the ECL immunosensor using CdTe@SiO2 as an emitter was proved to have a wide linear dynamic range from 1.0 pg mL-1 to 100 ng mL-1 with a low detection limit of 0.22 pg mL-1 (S/N ratio of 3). The ECL immunosensor also demonstrated satisfactory recovery and excellent reproducibility and stability, indicating that this method has prospects in practical application in the clinical diagnosis of AFP.