Preparation and characterization of poly (lactic-co-glycolic acid) microspheres for controlled release of osteogenic growth peptide / 中国组织工程研究

ABSTRACT

BACKGROUND:Previous animal studies have revealed that osteogenic growth peptide (OGP) applied locally or systemically could promote fracture healing. But the disadvantages of short in vivo half-life and low oral bioavailability limit its clinical application.OBJECTIVE: To study the encapsulation and delivery of synthetic OGP (sOGP) from biodegradable polymeric microspheres in vitro so as to choose better carrier for the future study.DESIGN: Grouping observation and comparative trail.SETTING: Laboratory of School of Life Science and Technology, Xi'an Jiaotong University.MATERIALS: sOGP was synthesized by Xi'an Langene Bio-science Co., Ltd. with Fmoc system. The purity of sOGP after purification was over 98 % identified by reverse phase high performance liquid chromatography, and the molecular weight of sOGP was 1 523 650, which was consistent with the theoretical value (Mr 1 523 750); the result of whole sequence analysis of sOGP was consistent with the theoretical sequence of OGP. Poly (lactic-co-glycolic acid) (PLGA,50:50, Mr 30 000; 75:25 Mr 80 000) was obtained from Shandong Medical Instrumental Institute (Ji'nan, China)METHODS: PLGA with a 50:50 or 75:25 lactide to glycolide ratio was used for microsphere preparation using a modified double emulsion solvent extraction Water-in-oil-in-water (w/o/w) technique. The surface structure and appearance of microsphere was observed under scanning electron microscope; particle size distribution of microsphere was counted by laser diffraction particle sizer; efficiency of encapsulation, release time and the structural integrity of sOGP released from PLGA were assessed using high performance liquid chromatography (HPLC).RESULTS: ①Spherical microspheres of sOG-PLGA were formulated successfully. The average particle diameter of the PLGA 50:50 microsphere was (19.6±4.5) μm, efficiency of encapsulation (83.9±4.2)% with (83.9±4.2) % drug-loading efficiency, while the PLGA 75:25 microspheres showed an average size of (35.8±3.6) μm, efficiency of encapsulation (65.6±6.8)% with (65.6±6.8)% drug-loading efficiency. ②HPLC results indicated that sOGP were not chemically altered,physically aggregated but presented a intact structure as the original sOGP. An initial burst release was observed for both PLGA microspheres, especially from PLGA 75:25. sOGP was released from PLGA 50:50 microsphere for 56 days,and from PLGA 75:25 microspheres for over 70 days. The cumulative release of sOGP from PLGA 50:50 for 35 days was significantly lower than from PLGA 75:25 (P ＜ 0.05).CONCLUSION: The controlled release of sOGP encapsulated within PLGA 50:50 is better than the delivery from PLGA 75:25. Moreover, the release time could meet the requirements for fracture or bone defect site.