The systematic investigation of the interaction of a new class of molecular materials with proteins through structure-optical signaling relationship studies has led to the development of efficient fluorescent probes that can detect and quantify serum albumins in biofluids without causing any denaturation.
Plaques
of amyloid fibrils composed of neuronal protein α-synuclein
are one of the hallmarks of Parkinson’s disease, and their
selective imaging is crucial to study the mechanism of its pathogenesis.
However, the existing fluorescent probes for amyloids are efficient
only in solution and tissue systems, and they are not selective enough
for the visualization of amyloid fibrils in living cells. In this
study, we present two molecular rotor-based probes RB1 and RB2. These
thiazolium probes show affinity to α-synuclein fibrils and turn-on
fluorescence response upon interactions. Because of its extended π-conjugation
and high rotational degree of freedom, RB1 exhibits a 76 nm red-shift
of absorption maxima and 112-fold fluorescence enhancement upon binding
to amyloid fibrils. Owing to its strong binding affinity to α-synuclein
fibrils, RB1 can selectively stain them in the cytoplasm of living
HeLa and SH-SY5Y cells with high optical contrast. RB1 is a cell-permeable
and noncytotoxic probe. Taken together, we have demonstrated that
RB1 is an amyloid probe with an outstanding absorption red-shift that
can be used for intracellular imaging of α-synuclein fibrils.
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