Thermosensitive porphyrin-incorporated hydrogel with four-arm PEG–PCL copolymer: Preparation, characterization and fluorescence imaging in vivo

A biodegradable thermosensitive hydrogel based on four-arm PEG–PCL copolymer was prepared with porphyrin as a fluorescence tag. Its structure and composition were characterized by FTIR, 1H NMR and GPC. Sol–gel–sol transition was evaluated by the test tube-inverting method and rheological analysis. The optical properties of hydrogel were investigated by UV–vis and fluorescence spectroscopy in vitro and by fluorescence imaging system in vivo. The results show that the thermosensitive hydrogel possesses dual function of fluorescence and injectability in vivo with good biocompatibility. Consequently it can be potentially applied in biomedical field as a visible implant for in situ monitoring.