Novel Benzothiazole Derivatives as Fluorescent Probes for Detection of β‑Amyloid and α‑Synuclein Aggregates

Deposits of β-amyloid (Aβ) and α-synuclein (α-syn) are the hallmark of Alzheimer’s disease (AD) and Parkinson’s disease (PD), respectively. The detection of these protein aggregates with fluorescent probes is particularly of interest for preclinical studies using fluorescence microscopy on human brain tissue. In this study, we newly designed and synthesized three push–pull benzothiazole (PP-BTA) derivatives as fluorescent probes for detection of Aβ and α-syn aggregates. Fluorescence intensity of all PP-BTA derivatives significantly increased upon binding to Aβ(1–42) and α-syn aggregates in solution. In in vitro saturation binding assays, PP-BTA derivatives demonstrated affinity for both Aβ(1–42) (<i>K</i>_d = 40–148 nM) and α-syn (<i>K</i>_d = 48–353 nM) aggregates. In particular, PP-BTA-4 clearly stained senile plaques composed of Aβ aggregates in the AD brain section. Moreover, it also labeled Lewy bodies composed of α-syn aggregates in the PD brain section. These results suggest that PP-BTA-4 may serve as a promising fluorescent probe for the detection of Aβ and α-syn aggregates