Magnetic graphene nanosheets based electrochemiluminescence immunoassay of cancer biomarker using CdTe quantum dots coated silica nanospheres as labels

A highly sensitive electrochemiluminescence (ECL) immunosensor for the detection of prostate specific antigen (PSA) was designed using biofunctionalized magnetic graphene nanosheets (G@Fe3O4) as immunosensing probes and CdTe quantum dots coated silica nanospheres (Si/QDs) as signal amplification labels. In this work, a sandwich-type immunosensor was fabricated, which was assembled on the surface of indium tin oxide glass (ITO). The analyte was detected in a home-made flow injection ECL (FI-ECL) cell through the immunosensor. Owing to the signal amplification of G@Fe3O4 composite and Si/QDs, the ECL measurement showed a great increase in detection signals compared with the unamplified method. Under optimal conditions, a wide detection range (0.003-50 ng mL(-1)) and a low detection limit (0.72 pg mL(-1)) were obtained through the sandwich-type immunosensor. The proposed strategy successfully demonstrated a reproducible, specific, and potent method that can be expanded to detect other proteins. (C) 2012 Elsevier B.V. All rights reserved.