Fabrication of a highly sensitive adenosine aptasensor based on covalent attachment of aptamer onto chitosan-carbon nanotubes-ionic liquid nanocomposite.

The present study describes the fabrication of a novel electrochemical aptasensor for the label-free determination of adenosine. The immobilization surface is prepared by the modification of a glassy carbon (GC) electrode with a robust nanocomposite containing multiwalled carbon nanotubes, ionic liquid and chitosan(MWCNTs-IL-CHIT). Amine-terminated 12-mer capture probe(ssDNA1) is covalently attached onto the nanocomposite using glutaraldehyde (GA) as the linking agent, a 32-mer adenosine-specific aptamer (ssDNA2) immobilized onto the electrode surface through hybridization with the ssDNA1 and methylene blue (MB) used as the redox probe. The peak current of MB decreased linearly with increasing adenosine concentration due to the formation of aptamer-adenosine complex and displacement of the aptamer from the modified electrode surface. The aptasensor showed a low detection limit of 150 pM and high sensitivity of 0.67 μAnM⁻¹ at a concentration range of up to 0.4 μM. Through the control experiments performed by using some other nucleosides such as guanosine, cytidine and uridine, the excellent specificity of this sensor toward adenosine detection is demonstrated. The potential applicability of the aptasensor is successfully applied for measuring adenosine concentration in blood serum and drug formulation samples.The herein described methodology may hold great promise for fabrication of other aptasensors and immunosensors.