Thermosensitive PCL‐PEG‐PCL hydrogels: Synthesis,characterization, and delivery of proteins

In this work, a biodegradable and injectable in situ gel‐forming controlled drug delivery system based on thermosensitive poly(ε‐caprolactone)‐poly(ethylene glycol)‐poly(ε‐caprolactone) (PCL‐PEG‐PCL) hydrogels was studied. A series of PCL‐PEG‐PCL triblock copolymers were synthesized and characterized by ¹H‐NMR and gel permeation chromatography (GPC). Thermosensitivity of the PCL‐PEG‐PCL triblock copolymers was tested using the tube inversion method. The in vitro release behaviors of two model proteins, including bovine serum albumin (BSA) and horseradish peroxidase (HRP), from PCL‐PEG‐PCL hydrogels were studied in detail. The in vivo gel formation and degradation of the PCL‐PEG‐PCL triblock copolymers were also investigated in this study. The results showed that aqueous solutions of the synthesized PCL‐PEG‐PCL copolymers can form in situ gel rapidly after injection under physiological conditions. The PCL‐PEG‐PCL hydrogels showed the ability to control the release of incorporated BSA and HRP. The released HRP was confirmed to conserve its biological activity by specific enzymatic activity assay. The in vivo gel formation and degradation studies indicated that PCL‐PEG‐PCL copolymers hydrogels can sustain at least 45 days by subcutaneous injection. Therefore, owing to great thermosensitivity and biodegradability of these copolymers, PCL‐PEG‐PCL copolymers hydrogels show promise as an in situ gel‐forming controlled drug delivery system for therapeutic proteins. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010