2.3 Bioimaging
Compared with traditional AIE luminophores with π conjugations,
nonconventional polysiloxanes enjoy unique superiority in bioimaging
owing to their water-solubility and good biocompatibility. With the
diverse reactive monomer, HBPSis exhibit varied cytotoxicity. For
example, the HBPSi synthesized from diethylene glycol and
3-aminopropyltriethoxysilane is less toxic than that synthesized from
3-aminopropyltriethoxysilane and
N-methyldiethanolamine.[38,44] Besides, the
cytotoxicity of HBPSis is proportional to their concentrations due to
the positively charged amino groups induced cell death. The modification
of L-glutamic acid or β -CD can reduce the cytotoxicity of HBPSi
and the toxicity of HBPSi derivatives is related to the amount of
L-glutamic acid or β -CD. For example, when the concentration of
HBPSi-CD reaches 5 mg/mL, more than 60% cells remain alive. After
incubation of HBPSi-GA with mouse osteoblast cells for 16 h at 37 ℃, the
cells exhibit blue luminescence. HBPSis and their derivatives can light
up cells and demonstrate potent application in bioimaging.
Lin et al. fabricated a polysiloxane-based fluorescent Schiff base (P1)
for the imaging of ferroptosis process.[58] The
polysiloxane main chain emitted blue fluorescence with the
rhodamine B in “turn off” state. In
the presence of Fe3+, the fluorescence of the
polysiloxane main chain is quenched with the rhodamine B switched to
“turn on” state. The P1 selectively penetrated apoptosis HeLa cells
and in situ monitored the Fe3+-induced
apoptosis via switched fluorescence emission.