Ionic polymers as double-capture agents in an aptamer lateral flow assay strip for point-of-care detection of ethyl carbamate using peroxidase-like activity of bimetallic NiCoO nanoparticles.

A novel aptamer LFA (Apt-LFA) strip is first constructed for ethyl carbamate (EC) detection, in which cationic polyethyleneimine (PEI) and anionic polyacrylamide (APAM) are used as double-capture agents. The black NiCoO nanoparticles (NCO NPs) encapsulated by EC1-34 aptamer are employed as recognition probes. The added EC will bind to EC1-34 aptamer on the probes, so that the test-line (T-line) immobilized with APAM can electrostatically capture the exposed NCO NPs. The control-line (C-line) sprayed with PEI can capture the excessive black recognition probes. The peroxidase-like activity of bimetallic NCO NPs is employed as signal amplification to improve the sensitivity of Apt-LFA strip. The naked eye discernible concentration of EC is 5 μg L and the detection limit (LOD) is as low as 1.36 μg L. The Apt-LFA strip has the advantages of strong stability, simplicity and low cost, which provide a new method for EC detection and offer a new way for designing LFA.