Preparation, characterization andin vitrorelease properties of ibuprofen-loaded microspheres based on polylactide, poly(϶-caprolactone) and their copolymers

In this paper, ibuprofen was encapsulated into microspheres by oil-in-water (o/w) emulsion solvent evaporation method. Biodegradable polymers with certain compositions and characteristics such as polylactide (PLA), poly(epsilon-caprolactone) (PCL) and their block copolymer were used to prepare the microspheres. The results indicate that, under the same processing conditions, the drug entrapment efficiency was similar (approximately 80%) for microspheres prepared with PLA and P(LA-b-CL) (78.7/21.3 by mole), but it was only 25.4% for PCL microspheres. The in vitro drug release rate decreased in the order of PCL, P(LA-b-CL) (78.7/21.3 by mole) and PLA microspheres. PCL microspheres showed more serious burst release during the first day (almost 80%) than P(LA-b-CL) (50%) and PLA microspheres (18%). The complete ibuprofen release duration from the last two kinds of microspheres exceeded 1 month. Characterization of the microspheres by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and polarized optical microscope (POM) revealed that ibuprofen was amorphous in PCL microspheres and partially crystalline in P(LA-b-CL) and PLA microspheres. The different release behaviour of ibuprofen from the three kinds of microspheres could be attributed to the different crystallinity of the studied polymers and drug dispersion state in polymer matrices. All the above results suggest that the copolymer with a certain ratio of lactide to -caprolactone could have potential applications for long-term ibuprofen release.

In vitro and in vivo studies of cyclosporin A-loaded microspheres based on copolymers of lactide and ɛ-caprolactone: Comparison with conventional PLGA microspheres

A hydrophobic peptide, cyclosporin A (CyA), was incorporated in microspheres based on poly(lactide-b-epsilon-caprolactone) (P(LA-b-CL), LA/CL (in molar ratio): 78.7/21.3 and 48.1/51.9) and poly(lactide-co-glycolide) (PLGA, LA/GA: 80/20) using oil-in-water (O/W) emulsion solvent evaporation method. The microspheres were characterized by SEM, DSC and X-ray diffraction, and CyA release rate was determined by HPLC. It was revealed that CyA can be efficiently loaded into all the microspheres (exceed 96%). Compared to PLGA microspheres, P(LA-b-CL) microspheres liberated CyA more rapidly. Within the first day, about 75, 50 and 12% of CyA released from P(LA-b-CL) (48.1/51.9), P(LA-b-CL) (78.7/21.3) and PLGA microspheres, respectively, which can be attributed to the partial crystallization occurring in P(LA-b-CL) microspheres. CyA levels in whole blood were also tested. In comparison with PLGA microspheres, P(LA-b-CL) microspheres provided a higher blood level of CyA. The maximum CyA concentration in whole blood (approximately 520, 450 and 400 ng ml(-1) for P(LA-b-CL) (48.1/51.9) P(LA-b-CL) (78.7/21.3) and PLGA microspheres, respectively) was reached at the second day post administration. And then P(LA-b-CL) microspheres showed a constant CyA level (about 100-200 ng ml(-1)) for extended periods of time (several weeks). Such CyA-loaded P(LA-b-CL) microspheres displaying higher CyA concentration during the first few days and similar constant blood CyA level thereafter showed more advantages than those prepared with PLGA and could meet clinical needs more efficiently.

Preparation and in vitro release behaviour of 5-fluorouracil-loaded microspheres based on poly (L-lactide) and its carbonate copolymers

A modified oil-in-oil (o/o) emulsion solvent evaporation technique was adopted to prepare 5-fluorouracil (5-Fu)-loaded poly (L-lactide) (PLLA) or its carbonate copolymer microspheres. The disperse phase was a drug:polymer solution using a solvent mixture of N,N-dimethylformamide (DMF) and acetonitrile and the continuous phase was liquid paraffin containing 1-10% (w/v) Span 80(R). The effects of preparative parameters, such as the composition of the inner oil phase, drug:polymer ratio, polymer concentration and agitation rate, on 5-Fu entrapment efficiency and microsphere characteristics were investigated. By introducing 25% (v/v) DMF into the inner oil phase, microspheres with high drug entrapment efficiency and an ameliorated burst effect were achieved. Using this modified method, microspheres with various particle sizes could be produced with a high 5-Fu entrapment efficiency (about 80%). In vitro drug release tests showed a burst release of 5-Fu from PLLA microspheres, followed by a sustained release over 50 days. In the case of poly (L-lactide-co-1,3-trimethylene carbonate) (PLTMC) and poly (L-lactide-co-2,2-dimethyl-1,3-trimethylene carbonate) (PLDTMC), the drug release could be continued for over 60 days.