DRUG RELEASE BEHAVIOR FROM POLYURETHANE GEL

Polyurethane gels, PTUG and PEUG were prepared from hydroxyl-terminated poly-(oxytetramethylene) (HT-PT) and hydroxyl-terminated poly(oxyethylene)-b-poly(oxytetramethylene)-b-poly-(oxyethylene) (HT-ETE), respectively. The release behavior of crystal violet from them was investigated. PEUG showed much larger swelling and hence a much larger release rate than PTUG. This result was explained by the presence of hydrophilic poly(oxyethylene) block in the network chains of PEUG. Compared with the corresponding segmented polyurethanes and polyurethaneureas prepared from HT-PT or HT-ETE, both PTUG and PEUG had larger release rate constants. This difference was explained by the supermolecular structural difference, i.e., the gels were homogeneous, while the segmented polymers were microphase separated. Drug release from the gel was defined by the diffusion of the drug through the drug delivery system (DDS) and the movement of the drug between the DDS and the aqueous environment, while in segmented polymers the partition of the drug in the heterogeneous matrix and the interaction between the drug and the hard segments greatly affected the drug release behaviour.