Elastic Polymeric Network Structure for Slow Release Drug Delivery Systems

Network structures based on poly(lactic acid)(PLA) were prepared for use as drug carriers to improve the effectiveness of drug therapy. A prepolymer precursor, with low molecular weight (5148), as determined by Gel Permeation Chromatography (GPC), was prepared by polycondensation of poly(lactic acid) with hydrolyzed ?-caprolactone. A second step that is necessary to increase the molecular weight and build up a network structure with elastic properties involved further polycondensation with stoichiometric amount of 1,6-hexamethylene diisocyanate to finally obtain Poly(ester urethane) with a molecular weight of 25680. The physicomechanical properties of the resulting polymeric networks were evaluated and the one that found to exhibit the best combination of tensile strength (3.83 MPa) and elongation at break (646%) was selected for slow release applications. Propolis and Doxorubicin as bioactive materials were incorporated into the selected sample and shaped in the form of circular discs with 0.9 cm diameter and 0.4 cm thickness. The discs containing the bioactive materials were subjected to a buffer solution at pH 7.4, and the release rates of Propolis and Doxorubicin were measured spectrophotometrically and found to be 35 µg/L/day and 70 µg/L/day for Propolis and Doxorubicin, respectively over a prolonged time of 15 days.