Design of PEG-aptamer two piece macromolecules as convenient and integrated sensing platform: application to the label free detection of small size molecules.

A novel strategy for the fabrication of electrochemical label free aptasensor for small size molecules is purposed, and the strategy has been demonstrated by the development of an aptasensor for ochratoxin (A). A long spacer chain of polyethylene glycol (PEG) was immobilized on screen printed carbon electrode (SPCE) via electrochemical oxidation of its terminal amino-group. The amino-aptamer was covalently linked to carboxy end of immobilized PEG to form two piece macromolecules. The designed immobilized macromolecules resulted in the formation of long tunnels on SPCE surface, while aptamer acted as gate of the tunnels. The aptamer gates were closed due to change in conformation of aptamer upon target analyte binding, decreasing the electrochemical signal. The decrease in electrochemical signal was used for the detection of target molecule.