Electrochemical impedance spectroscopy aptasensor for ultrasensitive detection of adenosine with dual backfillers

•EIS aptasensor was fabricated by coupling DTT and MCH as backfillers.•Dramatic improvement in LOD compared to that of DTT or MCH alone as backfiller.•The aptasensor showed high sensitivity and selectivity.•Linear range from 0.05 pM to 17 pM with LOD of 0.02 pM for adenosine detection.

A highly sensitive and label-free electrochemical impedance spectroscopy (EIS) aptasensor for the detection of adenosine was fabricated by co-assembling thiolated aptamer, dithiothreitol (DTT) and 6-mercaptohexanol (MCH) on gold electrode surface, forming Au/aptamer-DTT/MCH. The interfacial electron transfer resistance (Ret) of the aptasensor using [Fe(CN)6]3-/4- as the probe increased with adenosine concentration, and the change in Ret (∆Ret) against the logarithm of adenosine concentration was linear over the range from 0.05 pM to 17 pM with a detection limit of 0.02 pM. Compared to that of aptasensors fabricated with MCH or DTT alone as the backfiller, the detection limit was improved dramatically (LOD was 0.03 nM and 0.2 pM for Au/aptamer/MCH and Au/aptamer-DTT, respectively), which was attributed primarily to the coupling of the cyclic- and linear -configuration backfillers. The coupling showed remarkably higher resistance to nonspecific adsorption, leading to low background noise and high response signal. The aptasensor reported herein is applicable for the detection of other kinds of aptamer-binding chemicals and biomolecules.