Tyrosine-Conjugation Method for Evaluating BACE1 Activity Based on Silver Nanoparticles/Metal-Organic Framework Composites as Electrochemical Tags.

Beta-site secretase (BACE1) catalyzes the cleavage of amyloid precursor protein (APP), which process ultimately lead to plaque deposition in the brain of Alzheimer's disease (AD). Thus, accurate monitor of BACE1 activity is essential to screen inhibitors for AD treatment. This study develops a sensitive electrochemical assay for probing BACE1 activity based on silver nanoparticles (AgNPs) and tyrosine conjugation as tags and a marking method, respectively. An APP segment is firstly immobilized on aminated microplate reactor. Cytosine (C) rich sequence-templated AgNPs/Zr-based metal-organic framework (MOF) composite is modified by phenol groups, and then the prepared tag (ph-AgNPs@MOF) is captured in microplate surface by the conjugation reaction of phenolic groups between tyrosine and tag. After cleavage by BACE1, the solution containing ph-AgNPs@MOF tags is transferred to the screen-printed graphene electrode (SPGE) surface for voltammetric detection of AgNP signal. This sensitive detection for BACE1 provided an excellent linear relationship between 1 to 200 pM with a detection limit of 0.8 pM. Furthermore, this electrochemical assay is successfully applied for screening of BACE1 inhibitors. This strategy is also verified to be used for evaluation of BACE1 in serum samples.