Development of NIAD-4 derivatives for fluorescence-based detection of protein aggregates†

Impairment of protein quality control is a critical factor in the development of neurodegenerative disorders like Alzheimer's, Parkinson's and Huntington's disease, characterized by the accumulation of protein aggregates. As such, detection and monitoring of protein aggregates remains a crucial area of study. In this work, we synthesize a series of bithiophene derivatives based on a red emitting amyloid fluorophore NIAD-4. By molecular engineering, widened Stokes shifts and spectral tuning can be achieved in these derivatives. Through molecular docking and aggregation assays, we demonstrate the specificity of these derivatives towards protein fibrils over monomers and amorphous aggregates. Utilizing unbiased flow cytometry together with a cell viability indicator, we show that derivative NIAD-CNOET facilitates the discrimination of cells treated with and without preformed fibrils of α-synuclein, a model of the pathological hallmark of Parkinson's disease.