Fabrication of thermoresponsive micelles by functionalizing hydroxypropyl cellulose via azide-alkyne click reaction

In this work, we functionalized hydroxypropyl cellulose (HPC) by attaching tetraphenylethylene (TPE) via copper-catalyzed azide-alkyne cycloaddition (CuAAC). The obtained HPC-TPE samples displayed water-solubility, biocompatibility, fluorescence and thermoresponsive properties. The degree of substitution (DS_TPE) of HPC-TPE1 ~ 4 was determined to be 0.002, 0.006, 0.025, and 0.053, respectively. HPC-TPE could self-assemble into micelles in water with the hydrodynamic radius (R_h) ranging from 164 to 190 nm. Under different DS_TPE, HPC-TPE samples showed different lower critical solution temperature (LCST) behaviors in light transmittance, R_h and fluorescence. The critical transition temperatures in light transmittance for HPC-TPE1 ~ 4 solutions were 55–49 °C during the heating process, and were 44–40 °C during the cooling process, respectively. Moreover, HPC-TPE demonstrated a rapid and sensitive response to Fe³⁺ with ignoring interferences in the presence of other common metal ions, and could also be used to image 4T1 cells. Therefore, this work offered a general approach for the synthesis of functionalized polymers with promising applications in sensing and bioimaging.