A CdTe nanoparticle-modified hairpin probe for direct and sensitive electrochemical detection of DNA.

Detection of specific sequences of target DNA is of high importance in many fields, especially in medicinal diagnostics. DNA sensors should exhibit fast response to minute concentrations of the target sequence and have the ability to distinguish single-base mismatches from fully complementary target. This study focuses on the response of an electrochemical, CdTe nanoparticle-modified hairpin DNA sensor. The stem-loop structured probes and the blocking poly(ethylene glycol) (PEG) molecules were self-assembled on the gold electrode through S-Au bonding, to form a mixed monolayer employed as the sensing platform. Water-soluble CdTe nanoparticles were covalently attached to the hairpin probes (HPPs) and impedance spectroscopy was used for investigation of the electron transfer processes at a modified gold electrode before and after hybridization with the target DNA. The sensor showed reliable and sensitive detection of 4.7 fM of target. Although the selectivity of the sensor towards one-base mismatch targets needs to be improved, discrimination of non-complementary targets was achieved.