Effect of matrix type and inherent viscosity on the in vitro characteristics of carboplatin-poly (lactic-co-glycolic acid) microspheres

Objective: To study the effect of the type and inherent viscosity of poly( lactic-co-gly-colic acid) (PLGA) on drug release behavior from carboplatin-PLGA microspheres. Methods:Carboplatin-PLGA microspheres were prepared using W/O/W emulsion - solvent evaporation method. Particle size and morphology of the microspheres were analyzed under optical and electronic microscopes. Drug loading and the encapsulation efficiency were measured by ICP-MS. The in vitro release behavior was studied in PBS buffer (pH 7. 4). Results:The type and inherent viscosity of PLGA did not significantly impact the microspheres on particle size, drug loading and encapsulation efficiency, but produced quite different release profiles. The average size of microspheres ranged from 38 to 54μm, drug loading varied from 6. 4 to 7. 2μg·mg-1 and incorporation efficiency fluctuated from 16. 3% to 22. 7%. PLGA 50/50 gave a relatively rapider and higher burst release than PLGA 75/25. The burst release of carboplatin from PLGA (50/50,η=0. 18 andη=0. 53) microspheres within 2 hours was 55. 06% versus 83. 10% , and that from PLGA (75/25,η= 0. 19 andη=0.30) microspheres within 12 hours was 38.43% versus 44.04%. In the sustained release phase, drug release from PLGA 50/50 (η=0.53) microspheres o-beyed zero-order model, whereas the others featured the Higuchi model. PLGA (50/50,η=0. 18) and (75/25,η= 0. 19) slowly released the drug for up to 14 days, giving the release rate coefficient of 1. 18 h -1/2 and 2. 40 h-1/2 , respectively. Conclusion: The type and inherent viscosity of PLGA had very significant effect on drug release. PLGA 75/25 (η=0. 19) microspheres gave a relatively satisfying release profile of carboplatin.