Abstract
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 AuS 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 1.0×10−11M. The detection limit was estimated to be 1.7×10−18M. Also the biosensor showed good hybridization selectivity, stability and regeneration ability.
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