Blood-Brain Barrier Permeable 2-Phenylbenzothiazolyl Iridi-um Complexes as Inhibitors and Probes of Aβ Aggregation

Abstract

The aggregation of amyloid β (Aβ) peptides is a significant hallmark of Alzheimer’s Disease (AD) and the inhibition and detection of Aβ aggregates are important for the treatment and diagnosis of AD. Herein, a series of benzothiazole-based luminescent Ir(III) complexes <b>HN-1</b> to <b>HN-8</b> were reported, which exhibit appreciable Aβ aggregation inhibition ability <i>in vitro</i> and in living cells. In addition, they are capable of inducing a fluorescence turn-on effect when binding to Aβ fibrils and oligomers. Most importantly, compared to previously reported cationic metal complexes, the neutral Ir complexes reported here show optimal Log D values, which suggest these compounds should have enhanced blood brain barrier (BBB) permeability. Most importantly, <i>in vivo</i> studies show that the neutral Ir complexes <b>HN-2</b>, <b>HN-3</b>, and <b>HN-8</b> successfully penetrate the BBB and stain amyloid plaques in AD mice brains after a 10-day treatment via i.p. injection, which is unprecedented for Ir(III) complexes, and thus can be used as lead compounds for AD therapeutics development.