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.