EFFECTS OF PREPARATION CONDITIONS OF CISPLATIN-LOADED MICROSPHERES ONTHE IN-VITRO RELEASE

Microspheres from glycolide-L-lactide copolymers (PGLA) incorporating cis-diammine dichloroplatinum (II) (CDDP) were prepared with an O/O-ty pe emulsion method to study the effects of the preparation conditions on the in vitro release of CDDP. PGLA was virtually immiscible with CD DP. Homogeneous dimethyl formamide (DMF) solutions of CDDP and PGLA we re poured into liquid paraffin containing Span 80 as a surfactant, fol lowed by solvent evaporation at elevated temperatures. DMF was used as the common solvent of PGLA and CDDP because it had the lowest boiling point of their conventional common solvents. The influencing factors studied in this work include rate of temperature rise, operating tempe rature for solvent evaporation, Span 80 concentration, the molecular w eight of PGLA, CDDP loading and PGLA concentration. The effect of thes e preparation conditions on CDDP release was evaluated based on the ob servation of the resulting microspheres by scanning electron microscop y (SEM) and the plot of the amount of CDDP released against time. It w as found that the operating temperature for the solvent evaporation an d the rate of temperature rise to the operating temperature had a larg e effect on the release profile of CDDP. SEM observation of the cross- section of the microspheres revealed that the microsphere inside had a hole, although any significant deposit of micro-crystals of CDDP on t he microsphere surface was not noticed.