YOPRO-1: A Cyanine-Based Molecular Rotor Probe for Amyloid Fibril Detection

The widespread occurrence of amyloidosis in many neurodegenerative diseases, including Alzheimer's, highlights the urgent need for early detection methods. Traditional approaches often fall short in sensitivity, specificity, and the ability to operate within complex biological matrices. Fluorescence spectroscopy, which leverages the unique properties of extrinsic fluorescence sensors, has emerged as a promising avenue for amyloid detection. Thioflavin-T (ThT), while extensively utilized, faces several disadvantages such as poor blood-brain barrier penetration, short emission wavelength, and lack of sensitivity to oligomeric protein aggregates. These limitations necessitate the development of improved amyloid probes with enhanced properties for the better detection and understanding of neurodegenerative diseases. In this context, YOPRO-1, a cyanine-based molecular rotor probe, has been identified as a potent amyloid fibril sensor characterized by its turn-on fluorescence response and specificity for amyloid fibrils over native protein forms. Utilizing a variety of spectroscopic techniques, including steady-state emission, ground-state absorption, time-resolved fluorescence, and molecular docking, we demonstrate the superior selectivity and sensitivity of YOPRO-1 for amyloid fibrils. The probe exhibits a remarkable 245-fold increase in fluorescence intensity upon binding to insulin fibrils, which is a common amyloid model. This capability facilitates its application in complex biological matrices, such as high-percentage human serum, which has rarely been demonstrated by previous amyloid sensing probes. Furthermore, the commercial availability of YOPRO-1 avoids the challenges associated with the synthesis of specific probes, thereby marking a significant advancement in amyloid detection methodologies. Our findings highlight the potential of YOPRO-1 as a versatile and effective tool for the early diagnosis of amyloid-related diseases, offering a foundation for future therapeutic and diagnostic applications.