Colorimetric determination of amyloid-β peptide using MOF-derived nanozyme based on porous ZnO-CoO nanocages.

A sensitive and rapid colorimetric biosensor has been developed for determination of amyloid-β peptide (Aβ) and study of amyloidogenesis based on the high peroxidase-like activity of porous bimetallic ZnO-CoO nanocages (NCs). Due to the high binding ability of Aβ monomer to ZnO-CoO NCs, the catalytic activity of ZnO-CoO NCs can be significantly suppressed by Aβ monomer. This finding forms the basis for a colorimetric assay for Aβ monomer detection. The detection limit for Aβ monomer is 3.5 nM with a linear range of 5 to 150 nM (R = 0.997). The system was successfully applied to the determination of Aβ monomer in rat cerebrospinal fluid. Critically, the different inhibition effects of monomeric and aggregated Aβ species on the catalytic activity of ZnO-CoO NCs enabled the sensor to be used for tracking the dynamic progress of Aβ aggregation and screening Aβ inhibitors. Compared with the commonly used thioflavin T fluorescence assay, this method provided higher sensitivity to the formation of Aβ oligomer at the very early assembly stage. Our assay shows potential application in early diagnosis and therapy of Alzheimer's disease (AD).