An In Situ Study on Nanozyme Performance to Optimize Nanozyme-Strip for Aβ Detection

The nanozyme-strip is a novel POCT technology which is different from the conventional colloidal gold strip. It primarily utilizes the catalytic activity of nanozyme to achieve a high-sensitivity detection of target by amplifying the detection signal. However, previous research has chiefly focused on optimizing nanozyme-strip from the perspective of increasing nanozyme activity, little is known about other physicochemical factors. In this work, three sizes of Fe3O4 nanozyme and three sizes of CoFe2O4 nanozyme were used to investigate the key factors of nanozyme-strip for optimizing and improving its detection performance. We found that three sizes of Fe3O4 nanozyme all gather at the bottom of the nitrocellulose (NC) membrane, and three sizes of CoFe2O4 nanozyme migrate smoothly on the NC membrane, respectively. After color development, the surface of NC membranes distributed with CoFe2O4 peroxidase nanozymes had significant color change. Experimental results show that CoFe2O4 nanozymes had better dispersity than Fe3O4 nanozymes in an aqueous solution. We observed that CoFe2O4 nanozymes with smaller particle size migrated to the middle of the NC membrane with a higher number of particles. According to the results above, 55 ± 6 nm CoFe2O4 nanozyme was selected to prepare the nanozyme probe and achieved a highly sensitive detection of Aβ42Os on the nanozyme-strip. These results suggest that nanozyme should be comprehensively evaluated in its dispersity, the migration on NC membrane, and the peroxidase-like activity to determine whether it can be applied to nanozyme-strip.