CdS nanoparticles functionalized colloidal carbon particles: preparation, characterization and application for electrochemical detection of thrombin.

A novel and simple method for preparing cadmium sulfide nanoparticles (CdS NPs) functionalized colloidal carbon particles (CPs) has been successfully developed by in situ growing abundant CdS NPs on the surfaces of monodisperse carbon particles (CdS/CPs). The obtained CdS/CPs conjugates as signal amplification labels were further used for the ultrasensitive determination of thrombin. The CdS/CPs conjugates were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-visible absorption spectrum (UV). The protein electrical detection involves a dual binding event, based on thrombin linked to the CdS/CPs tags and glass surface by the specific aptamer-protein affinity interactions and a succedent electrochemical stripping transduction. Owing to the high-content CdS NPs on carbon particles, this assay allowed a desirable detection limit of 6.0 × 10(-17)M, which was 1000 times lower than that of only using CdS NPs as labels in the control experiments. This protocol exhibited excellent selectivity against these common proteins such as bovine plasma albumin, lysozyme and hemoglobin. The signal amplification approach proposed here provides a facile, cost-effective method for the ultrasensitive determination of thrombin in the practical samples.