Electrochemiluminescence of CdSe quantum dots for immunosensing of human prealbumin

We describe a non-labeled electrochemiluminescence (ECL) immunosensor based on CdSe quantum dots (QDs) for the detection of human prealbumin (PAB, antigen). The immunosensor was fabricated by layer by layer coupled with nanoparticle-amplification techniques. After two gold nanoparticle layers were self-assembled onto the gold electrode surface through cysteamine, anti-PAB (antibody) were conjugated with –COOH groups of both the CdSe QDs and cysteine, which were linked to the gold nanoparticle-modified electrode. The principle of ECL detection was that the immunocomplex inhibited the ECL reaction between CdSe QDs and K2S2O8, which resulted in the decrease of ECL intensity. On the one hand, the immunocomplex increased the steric hindrance. On the other hand, the immunocomplex maybe inhibit the transfer of K2S2O8 to the surface of the CdSe QD-electrode. The PAB concentration was determined in the range of 5.0 × 10−10 to 1.0 × 10−6 g mL−1, and the detection limit was 1.0 × 10−11 g mL−1. The developed CdSe QD-based ECL immunosensor provides a rapid, simple, and sensitive immunoassay protocol for protein detection, which could be applied in more bioanalytical systems.