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Two types of injectable system using thermosensitive chitosan (chitosan-g-NIPAAm), hydrogel and microparticles (MPs)-embedded hydrogel were developed as drug carriers for controlled release and their pharmaceutical potentials were investigated. 5-Fluorouracil (5-FU)-loaded, biodegradable PLGA MPs were prepared by a double emulsion method and then simply mixed with an aqueous solution of thermosensitive chitosan at room temperature. All 5-FU release rates from the hydrogel matrix were faster than bovine serum albumin (BSA), possibly due to the difference in the molecular weight of the drugs. The 5-FU release profile from MPs-embedded hydrogel was shown to reduce the burst effect and exhibit nearly zero-order release behavior from the beginning of each initial stage. Thus, these MPs-embedded hydrogels, as well as thermosensitive chitosan hydrogel, have promising potential as an injectable drug carrier for pharmaceutical applications.

Star-shaped PLA-heparin (sPLA-Hep) was prepared by coupling heparin to the star-shaped PLA (sPLA) reaction using carbonyldiimidazole (CDI) chemistry. Hydroxyl groups of sPLA were activated by CDI for the reaction with the remained amino-terminal groups of heparin. The surface heparin content of sPLA-Hep was measured to be 1.43 microg/cm(2). sPLA-Hep-coated surface has shown higher hydrophilicity than control surface. The clotting time of sPLA-Hep measured by activated partial thromboplastin time (APTT) was significantly prolonged when compared with sPLA and linear PLA-Hep. sPLA-Hep surface demonstrated lower protein adsorption and platelet adhesion than control sPLA surface. In addition, fibroblast culture on the sPLA-Hep surface showed the enhanced cell spreading area compared with the sPLA surface. Obtained results suggest that the incorporation of heparin to sPLA is effective in curtailing the surface induced-thrombosis and in manipulating the cell interaction. sPLA-Hep could be applied as blood/tissue compatible biodegradable materials for implantable medical devices and tissue engineering.

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