Biodegradable Thermosensitive Injectable Poly(ε-caprolactone)–Poly(ethylene glycol)–Poly(ε-caprolactone) Based Hydrogels for Biomedical Applications

Abstract

A series of biodegradable poly(ε-caprolactone)–poly(ethylene glycol)–poly(ε-caprolactone) (PCL–PEG–PCL) (PCEC) triblock copolymers had been successfully synthesized by ring-opening polymerization of ε-caprolactone initiated by PEG, which were characterized by proton nuclear magnetic resonance analysis (1H NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The gel–sol phase transition diagram of synthesized copolymers was recorded using test tube inverting method. PCECs could form injectable solutions via self-assembly and automatically turned into non-flowing gels at physiological temperatures. Their aqueous solution displayed special gel–sol transition behavior with temperature increasing from 0 to 60°C, when the polymer concentration was above corresponding critical gel concentration (CGC). In vitro release experiments at pH 7.4 showed that after 24 h at least approximately 75–80% of doxorubicin (DOX) can be protected from enzyme or hydrolytic degradation. Therefore, thermosensitive PCECs have many advantages, such as simple drug formulation, no organic solvent, a sustained drug release behavior.