A sensitive and selective strategy to identify and differentiate amyloid beta (Aβ) aggregates remains a challenge in amyloid protein research. Here we show that the luminescent complex cis-[Ru(phen)2 (3,4Apy)2]2+ (RuApy, 3,4APy = 3,4-diaminopyridine, phen = 1,10-phenanthroline) presents an unique sensitivity and selectivity to the aggregation process of Aβ1-40 and its Aβ1-28, Aβ11-22 and Aβ29-40 variants. The complex is a valuable probe for time-resolved imaging of Aβ aggregates, as it displays a long-lived emission without quenching the short-lived fluorescence of the peptide. Strikingly, these luminescence lifetime patterns are characteristic of the specific Aβ:complex interactions for Aβ1-28 (1.7 and 18.5 ns), Aβ11-22 (1.8 and 22.8 ns) and Aβ1-40 (2.8 and 7.4 ns), thereby enabling differentiation between Aβ peptide aggregates.
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