An Ultrasensitive Biosensing Platform Employing Acetylcholinesterase and Gold Nanoparticles.

Enzyme-linked immunosorbent assay (ELISA) is a well-known strategy for biomarker detection with a color change, which can be seen by the naked eyes. However, the moderate sensitivity of conventional ELISA limits its applications in many cases where the concentrations of biomarker are very low, such as cancer diagnosis. Here we describe an ultrasensitive colorimetric assay based on acetylcholinesterase (AChE)-catalyzed hydrolysis reaction, whose products trigger the aggregation of gold nanoparticles (AuNPs), causing a distinct color change of the solution from red to purple. This enhanced colorimetric immunoassay offers extremely high sensitivity and specificity. In this study, we employed enterovirus 71 (EV71), the major cause of hand, foot, and mouth disease (HFMD), as a model to evaluate the analytical performance of the plasmonic immunoassay.