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.