Injectable Thermosensitive Hydrogels for Intra-Articular Delivery of Methotrexate

Intra-articular drug delivery is the preferred approach for targeting pharmacologic treatment directly at the joints to reduce undesirable side effects associated with systemic drug delivery. In this study, a controlled delivery system of methotrexate (MTX) based on injectable thermosensitive poly(epsilon-caprolactone)-poly (ethylene glycol)-poly(epsilon-caprolactone) (PCL-PEG-PCL, PEP) hydrogels was developed for the intra-articular drug delivery. The thermosensitive PEP copolymers were prepared by ring-opening polymerization. The synthesized PEP copolymers were characterized for their structure, composition, and the sol-to-gel transition. The in vitro MTX release from the PEP hydrogels was studied. MTX plasma concentration following intra-articular injection into healthy rats was determined by HPLC. Biocompatibility was confirmed by histology analysis after the intra-articular injection. The synthesized PEP copolymers aqueous solutions formed in situ gel rapidly after the injection. PEP hydrogels showed the ability to control the release of incorporated MTX. Following intra-articular injection, the PEP hydrogels decreased the clearance rate of MTX in the joint cavity. The maximum plasma concentrations of MTX in rats injected with free MTX were threefold higher than that of the groups injected with MTX hydrogels. These results suggest that the intra-articular delivery of the PEP hydrogels may be a viable strategy for the controlled release of drugs for treating arthritis diseases. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 2139-2145, 2011