RESUMO
BACKGROUND:In literatures, the recombinant human bone morphogenetic protein-2 (rhBMP-2) loaded microcapsules can be fabricated by double emulsion solvent evaporation method with different organic solvents, such as methylene chloride, ethyl acetate or their mixture. But so far it is not determined yet which one is better. OBJECTIVE: To optimize the preparation method of microcapsules encapsulating rhBMP-2 and to compare the effects of different organic solvents on the microcapsules. METHODS:Polylactic acid-polyethylene glycol-polylactic acid copolymer as microcapsules was used to prepare rhBMP-2 loaded microcapsules with double emulsion solvent evaporation method. Four kinds of organic solvents, methylene chloride (group A), mixture of methylene chloride and ethyl acetate (group B), ethyl acetate (group C) and acetyl acetone (group D) were chosen as oil phases to compare their effects on microcapsule's morphology, diameter, and encapsulation efficiency. Passage 3 bone marrow mesenchymal stem cels from rats were co-cultured with prepared microcapsules for 14 days, and then alkaline phosphatase activity was detected. RESULTS AND CONCLUSION:Compared with the other organic solvents, dichloromethane could cause microcapsules with the smaler and more uniform shape (4-10 microns) and the highest encapsulation efficiency; the microcapsules prepared by mixture of methylene chloride and ethyl acetate had relatively wide size distribution and moderate encapsulation efficiency; the microcapsules prepared by acetylacetone were difficult to form and keep the bioactivity of rhBMP-2. After cultured with rat bone marrow mesenchymal stem cels for 14 days, the alkaline phosphatase activity in groups A, B and C was significantly higher than that in group D and there was no significant difference between group A and group B; the alkaline phosphatase activity in groups A and B was significantly higher than that in group C (P< 0.05). The results show the rhBMP-2-loaded microcapsules prepared by methylene chloride as organic solvent have good shape, high encapsulation efficiency, and good biological activity.