Cationic Organochalcogen with Monomer/Excimer Emissions for Dual-Color Live Cell Imaging and Cell Damage Diagnosis

Studies
on the development of fluorescent organic molecules with different
emission colors for imaging of organelles and their biomedical application
are gaining lots of focus recently. Here, we report two cationic organochalcogens 1 and 2, both of which exhibit very weak green
emission (Φ1 = 0.12%; Φ2 = 0.09%)
in dilute solution as monomers, but remarkably enhanced green emission
upon interaction with nucleic acids and large red-shifted emission
in aggregate state by the formation of excimers at high concentration.
More interestingly, the monomer emission and excimer-like emission
can be used for dual color imaging of different organelles. Upon passively
diffusing into cells, both probes selectively stain nucleoli with
strong green emission upon 488 nm excitation, whereas upon 405 nm
excitation, a completely different stain pattern by staining lysosomes
(for 1) or mitochondria (for 2) with distinct
red emission is observed because of the highly concentrated accumulation
in these organelles. Studies on the mechanism of the accumulation
in lysosomes (for 1) or mitochondria (for 2) found that the accumulations of the probes are dependent on the
membrane permeabilization, which make the probes have great potential
in diagnosing cell damage by sensing lysosomal or mitochondrial membrane
permeabilization. The study is demonstrative, for the first time,
of two cationic molecules for dual-color imaging nucleoli and lysosomes
(1)/mitochondria (2) simultaneously in live
cell based on monomer and excimer-like emission, respectively, and
more importantly, for diagnosing cell damage.