Electrochemical aptasensor for the detection of adenosine by using PdCu@MWCNTs-supported bienzymes as labels

A highly sensitive electrochemical adenosine aptasensor was fabricated by covalently immobilizing 3′-NH 2 -terminated capture probe (SSDNA1) and thionine (TH) on Au–GS modified glassy carbon electrode. 3′-SH-terminated adenosine aptamer (SSDNA2) was adsorbed onto palladium/copper alloyed supported on MWCNTs ( [email protected] )-conjugated multiple bienzymes, glucose oxidase (GOx), and horseradish peroxidase (HRP) (SSDNA2/ [email protected] /HRP/GOx). Then, it was immobilized onto the electrode surface through the hybridization between the adenosine aptamer and the capture probe. The signal was amplified based on the gradual electrocatalytic reduction of GOx-generated hydrogen peroxide by the multiple HRP through the mediating ability of the loaded multiple TH. However, the peak current of TH decreased in the presence of adenosine because the interaction between adenosine and its aptamer made SSDNA2/ [email protected] /HRP/GOx release from the modified electrode . Various experimental parameters have been optimized for the detection of adenosine and tests for selectivity , reproducibility and stability have also been performed. Under the optimal condition, the proposed aptasensor displayed a wide linear range (10–400   nM) with the low detection limit (2.5   nM), which has been applied in human serum samples with satisfactory results. Thus, the combination of Au–GS as a sensor platform and [email protected] /HRP/GOx as labels can be a promising amplification strategy for highly sensitive adenosine detection.