Electrochemical Biosensor for Detection of Adenosine Based on Structure-Switching Aptamer and Amplification with Reporter Probe DNA Modified Au Nanoparticles

In the present study, an electrochemical sensing strategy for highly sensitive detection of small molecules was developed based on switching structures of aptamers from DNA/DNA duplex to DNA/target complex. A gold electrode was first modified with gold nanoparticles (AuNPs), and thiolated capture probe was immobilized onto the electrode via sulfur-gold affinity. Then, a "sandwich-type" strategy was employed, which involved a linker DNA containing antiadenosine aptamer sequence and reporter DNA loaded on AuNPs. In the presence of adenosine, the aptamer part bound with adenosine and folded to the complex structure. As a result, the reporter probes together with AuNPs were released into solution and reduced a decrease in peak current. With the enhancement effect of AuNPs, a detection limit as low as 1.8 x 10(-10) M for adenosine was achieved. The sensor exhibited excellent selectivity against other nucleosides and could be used to detect adenosine from real human serum samples.