Electrochemical DNA/aptamer biosensors based on SPAAC for detection of DNA and protein

Electrochemical DNA/aptamer (E-DNA/aptamer) biosensors based on target-induced change in conformation of surface-anchored oligonucleotides have been developed in recent years. In order to improve electrode surface modification versatility, we developed a simple approach for fabrication of DNA-conjugated electrochemical platform on screen-printed electrodes for the detection of DNA and protein. The conjugation of oligonucleotides was conducted based on a copper-free strain-promoted azide-alkyne cycloaddition (SPAAC), in which the dibenzocyclooctyne (DBCO)-modified oligonucleotides were covalently conjugated to azide-terminated gold-plated screen-printed carbon electrodes. As a proof-of-principle, we employed the p53 DNA probe and anti-VEGF165 DNA aptamer as the receptors to determine the versatility of the electrode surface modification. The proposed E-DNA/aptamer sensors showed a limit of detection of 0.76 nM for p53 DNA target and 8.2 pM for VEGF165 protein, respectively. In addition, both sensors demonstrated satisfactory stability in 50% fetal bovine serum samples. The results indicated that the E-DNA/aptamer sensors fabricated by SPAAC reaction performed well when compared to those fabricated via the conventional gold-thiol coadsorption or CuAAC reaction. The proposed approach has a great potential to fabricate biosensors on less-expensive substrates for detection of DNA or proteins.