Electrochemical protein detection exploring redox cation-DNA interaction for signal enhancement

A simple DNA-redox cation interaction enhancement strategy has been developed for improving the sensitivity of electrochemical immunosensors for protein detection. Instead of labeling with fluorophores or redox-active groups, the detection antibodies were tethered with DNA single strands. Based on the electrostatic interaction between redox cations ([Ru(NH3)6]3+) and negatively charged DNA backbone, enhanced electrochemical signals were obtained. Human chorionic gonadotropin (hCG) detection has been performed as a trial analysis. A linear response up to 25 mIU/mL and a detection limit of 1.25 mIU/mL have been achieved, both comparable with standard enzyme-linked immunosorbent assay (ELISA) tests. The method also shows remarkable selectivity towards hCG over other hormones such as thyroid stimulating hormone (TSH) and follicle stimulating hormone (FSH). By and large, our approach bears the merits of cost effectiveness and simplicity of instrumentation in comparison with conventional optical detection methods.