Dual stimuli-responsive biocompatible fluorescent hyperbranched poly(β-aminoester) for the detection of physiological temperature and pH and controlled delivery.

Abstract

The sustainable synthesis of biocompatible multi-stimuli-responsive fluorescent hyperbranched polymers is an important and challenging research topic. Herein, we report the synthesis of temperature- and pH-responsive fluorescent hyperbranched poly(β-aminoester). The hyperbranched polymer structure was thoroughly analyzed <i>via</i> NMR, IR, DLS and TEM analyses, and the degree of branching was found to be 75%. Thermal analysis revealed that the polymers are thermally stable up to 180 °C and have a glass transition temperature of around -5 °C. At pH 7, the cloud point temperature (<i>T</i>_cp) was determined to be 36 °C, which is extremely close to the physiological temperature of the human body; this temperature further depends on the pH of the medium. The fluorescence intensity shows a linear dependence on temperature and pH, supporting its potential as a temperature and pH sensor. Drug release studies demonstrate the potential of the hyperbranched polymer for controlled drug delivery, showing the most sustained release under physiological conditions (36 °C and pH 7).