Heparin release from thermosensitive hydrogels

Thermosensitive hydrogels (TSH) were synthesized and investigated as heparin releasing polymers for the prevention of surface induced thrombosis. TSH were synthesized with N-isopropyl acrylamide (NiPAAm) copolymeriaed with butyl methacrylate (BMA) (hydrophobic) or acrylic acid (AAc) (hydrophilic) comonomers. The incorporation of hydrophobic and hydrophilic omonomers strongly influences the swelling/shrinking behavior of TSH. Upon deswelling, els containing the hydrophobic comonomer formed a skin-type layer, which acted as a rate controlling membrane, while the hydro-philic comonomer greatly increased gel swelling, relative to NiPAAm. Equilibrium swelling in isotonic PBS and deswelling kinetics of the synthesized gels were examined at various temperatures. The load-ing of heparin into the different gels was studied as a function of temperature, solution concentration, and gel composition. The release kinetics of heparin was found to be influenced by gel composition and loading temperature; the release correlated with the gel deswelling kinetics. In the case of Ni-PAAm/BMA gel, the release prottle of heparin was affected by temperature dependent properties of the skin-type diffusional barrier formed on the gel surtace. Key words: Thermosensitive hydrogels; Heparin releasing polymers; Poly (N-isopropylacrylamide) Thermosensitve hydrogels (TSH) exhibi