Unconventional Fluorescent and Multi-responsive Polysiloxane: Synthesis, Characterization and Biological Applications

Owing to their high significance in fundamental study and diverse applications, stimuli-responsive and fluorescent polymers, particularly those with cluster-triggered emission (CTE) featured by non-conjugated chromophores, have drawn tremendous attention in recent years. In this work, fluorescent and multi-responsive polysiloxane (FRPS) was synthesized by hydrolytic condensation polymerization of 3-aminopropyl methyl diethoxysilane (APMS) with 3-(N-isopropyl propionamide) iminopropyl methyl diethoxysilane (APMS-NIP), which was formed in situ through aza-Michael addition between APMS and N-isopropyl acrylamide. FRPS was not only highly sensitive to temperature, pH and CO₂ in water, but also showed an enhanced and stimuli-adjustable fluorescence emission. The effects of monomer feeding, pH and CO₂ on its lower critical solution temperature and fluorescent property were investigated. FRPS fluorescence emission was ascribed to CTE mechanism. In addition, FRPS was shown to be highly potential as physiological indicator for cell imaging, and for controlled release and trace detection of doxorubicin. This study provides therefore a type of stimuli-responsive and fluorescent material for potential applications in biomedical fields, and it is also of great significance for understanding of the fluorescence mechanism of polysiloxane-based stimuli-responsive polymers.