Motor-based autonomous microsensor for motion and counting immunoassay of cancer biomarker.

A motor-based autonomous microsensor is proposed for in situ visualization immunoassay of cancer biomarkers through motion readout or tag counting. The microsensor is prepared by functionalizing a newly designed gold-nanoparticle-modified self-propelled polyaniline/Pt (AuNP/PANI/Pt) micromotor with capture antibody. The autonomous movement of the microsensor in the fuel-enhanced sample mixture results in the fast and selective recognition of the protein target and subsequent loading of the secondary-antibody-modified glycidyl methacrylate microspheres (GMA), which slows down the movement of the sensing microengine. The velocity of the microsensor and the number of GMA conjugated on the microsensor can be conveniently visualized using optical microscopy. They are negatively and positively correlated with the target concentration, respectively. Therefore, the microsensor can conveniently distinguish the concentration of carcinoembryonic antigen in a range of 1-1000 ng/mL. The motor-based microsensor can be easily prepared in batch using AuNP/PANI/Pt. The whole detection procedure for protein target can be completed in 5 min without any washing and separation step. This method shows considerable promise for diverse clinical and diagnostic applications.