Water-Soluble Unconventional Hyperbranched Polyborosiloxane Derivatives for Temperature Sensing in Living Cells

Fluorescent polymeric thermometers, despite their noninvasive detection and rapid response for intracellular temperature monitoring, face challenges in achieving excellent biocompatibility and high sensitivity. Herein, we synthesized a water-soluble unconventional temperature-sensitive fluorescent polymer (P2) through terminally grafting poly(<i>N</i>-vinylcaprolactam) (PNVCL) onto hyperbranched polyborosiloxane (P1). The P2 exhibited efficient red-light emission and good photostability. Particularly, when the temperature rises, the PNVCL units transform from hydrophilic to hydrophobic, resulting in the dislocation of local segments of P2, suppressing radiative transitions and simultaneously weakening its through-space conjugation, further reducing its fluorescence intensity, and endowing the P2 with a high temperature-sensing sensitivity of 10.06% °C^-1. Finally, the real-time monitoring of intracellular temperature variation was further conducted. This work not only develops promising thermochromic materials for intracellular temperature sensing but also provides further insight into the temperature-sensing mechanism of unconventional fluorescent polymers.