Chemiluminescence aptasensor for cocaine based on double-functionalized gold nanoprobes and functionalized magnetic microbeads

A novel chemiluminescence (CL) aptasensor for highly sensitive detection of small-molecule targets using cocaine as a model analyte was developed in the present study. For the proposed aptasensor, the aptamers were immobilized on the surface of gold nanoparticles (AuNPs) functionalized magnetic microbeads (MB-AuNPs) and then hybridized with the signal DNA on the double-functional gold nanoprobes (DF-AuNPs) modified with horseradish peroxidase (HRP). When cocaine was introduced, a competition for the aptamer between cocaine and the signal DNA occurred and the gold nanoprobes were forced to dissociate from the MB-AuNPs surface based on the structure switching of the aptamer. The CL signals of Luminol-H2O2-HRP-PIP system were proportional to the concentration of cocaine. A linear range was obtained when the concentrations of cocaine were from 1 x 10(-9) to 1 x 10(-8) M with the detection limit of 0.48 nM (3 sigma), much lower than those achieved by other methods. This new system can be easily extended to a variety of small-molecules, protein, and tumor cell analysis.