Self-Assembly of Superquenched Gold Nanoparticle Nanosensors for Lighting up BACE-1 in Live Cells.

Abstract

The β-site amyloid precursor protein-cleaving enzyme 1 (BACE-1) plays a key role in Alzheimer's disease (AD) pathogenesis and is regarded as a valuable biomarker for AD diagnosis and treatment. The reported BACE-1 assay often suffers from laborious procedures, large sample consumption, and unsatisfactory sensitivity with high background signals. Herein, we report the self-assembly of superquenched gold nanoparticle (AuNP) nanosensors for lighting up the BACE-1 in live cells. Through the self-assembly of both fluorophore-labeled peptide probes and quencher-labeled assistant DNAs on the surface of a single AuNP, a superquenched AuNP nanoprobe is obtained with a high quenching efficiency of 98.37% and a near-zero background fluorescence. The presence of target BACE-1 induces a distinct fluorescence signal as a result of the BACE-1-catalyzed cleavage of peptide probe and the subsequent release of abundant fluorophore moieties from the AuNP nanoprobe. The fluorescence signal can be directly visualized by single-molecule imaging and easily quantified by single-molecule counting. This nanosensor involves only a single nanoprobe for the one-step homogeneous detection of the BACE-1 activity without the requirements of any antibodies and separation steps, and it possesses good selectivity and high sensitivity with a low detection limit of 26.48 pM. Moreover, it can be employed to screen BACE-1 inhibitors and analyze kinetic parameters. Especially, this nanoprobe possesses good stability and can be easily transferred into live cells for the real-time imaging of cellular BACE-1 activity, providing a new platform for BACE-1-associated research and early diagnosis of Alzheimer's disease.