A high-performance DNA biosensor based on the assembly of gold nanoparticles on the terminal of hairpin-structured probe DNA

An ultrasensitive electrochemical DNA biosensor has been developed based on the assembly of highly conductive gold nanoparticles (AuNPs) on the free terminal of hairpin-structured probe DNA . The hairpin probe DNA was first immobilized on a gold electrode surface through Au S bond. Then the thioglycolic acid (TGA) was grafted on the 3′-end of hairpin DNA via the carboxylic-amino condensation reaction . Followed by, the AuNPs were further attached through reaction with the thiol-group of TGA. Thus, a highly conductive biointerface with ultralow charge-transfer resistance was obtained. Quantitative analysis exhibited that the target DNA could be detected over the range from 1.0   ×   10 −17 to 1.0   ×   10 −11   M. The detection limit was estimated to be 1.7   ×   10 −18   M. Also the biosensor showed good hybridization selectivity , stability and regeneration ability.