Detection and disaggregation of amyloid fibrils by luminescent amphiphilic platinum() complexes

Cyclometallated Pt( ii ) complexes possessing hydrophobic 2-phenylpyridine (ppy) ligands and hydrophilic acetonylacetone (acac) ligands have been investigated for their ability to detect amyloid fibrils via luminescence response. Using hen egg-white lysozyme (HEWL) as a model amyloid protein, Pt( ii ) complexes featuring benzanilide-substituted ppy ligands and ethylene glycol-functionalized acac ligands demonstrated enhanced luminescence in the presence of HEWL fibrils, whereas Pt( ii ) complexes lacking complementary hydrophobic/hydrophilic ligand sets displayed little to no emission enhancement. An amphiphilic Pt( ii ) complex incorporating a bis(ethylene glycol)-derivatized acac ligand was additionally found to trigger restructuring of HEWL fibrils into smaller spherical aggregates. Amphiphilic Pt( ii ) complexes were generally non-toxic to SH-SY5Y neuroblastoma cells, and several complexes also exhibited enhanced luminescence in the presence of Aβ 42 fibrils associated with Alzheimer's disease. This study demonstrates that easily prepared and robust (ppy)Pt II (acac) complexes show promising reactivity toward amyloid fibrils and represent attractive molecular scaffolds for design of small-molecule probes targeting amyloid assemblies. Amphiphilic Pt( ii ) complexes exhibit turn-on luminescence response to HEWL fibrils. In one case, incubation of pre-formed fibrils with a Pt complex results in morphological change from larger fibrillar structures to smaller spherical aggregates.