Platinum-gold alloy nanoparticles and horseradish peroxidase functionalized nanocomposite as a trace label for ultrasensitive electrochemical detection of thrombin.

A novel tracer, platinum-gold alloy nanoparticles (Pt-AuNPs) and horseradish peroxidase (HRP) functionalized single-walled carbon nanotubes (SWCNTs) composite, is employed to label the secondary thrombin aptamer for constructing an ultrasensitive electrochemical aptasensor. Thionine, immobilized on functionalized SWCNTs, provides a pair of distinguished redox peak for electrochemical detection. Both the high-content Pt-AuNPs and HRP on SWCNTs amplify the electrochemical signal of thionine through electrocatalytic reduction of H(2)O(2). Differential pulse voltammetry (DPV) is employed to detect thrombin with different concentrations. The reduction peak current is logarithmically related to the concentration of thrombin in an extremely wide range from 10 fM to 5 nM with a detection limit of 3.6 fM. The dual signal amplification of Pt-AuNPs and HRP functionalized nanocomposite provides a promising way for ultrasensitive assay in electrochemical aptasensors.