Study On Plga Microspheres Loaded With Granulocyte-Macrophage Colony-Stimulating Factor

Human granulocyte-macrophage colony-stimulating factor (GM-CSF), by exerting it's proliferate and differentiation effects on granulocytes, macrophages and eosinophilic precursors, has been in clinical trials in accelerating the recovery of neutrophil levels and also widely studied as the adjuvant in varied kinds of vaccine.However, as many as protein therapeutics, the plasma half-life of hGM-CSF is considerably short and frequent injection is required, causing problems of patients compliance.Research effort to develop long acting and sustained release systems have not yet resulted in a successful commercial product. Activity loss in formulation processes or the release period is the major technical hurdle in development of sustained release depot.The primary objective is to exam a new microencapsulation process using a unique Aqueous-Aqueous emulsion system. Stucture delicate GM-CSF was mixed with a Dextran solution then emulsified into a PEG solution containing sodium alginate. The proteins preferentially partitioned into the dextran depersed phase and lyophilized to solid particles, 1-5μm in diameter. The particles were then encapsulated into PLGA microspheres, 60-120μm in diameter.A TF-1 cell proliferation assay and a SEC-HPLC analysis after each formulation step indicated that bioactivity and interrity of rhGM-CSF was preserved during the formulation process. The dextran glassy particles also played a role in improvement of protein release kinetics by minimizing initial burst and incomplete release. For a given protein loading, increasing dextran content ensured complete release, while limiting dextran content minizing intial burst. GM-CSF released from the microsphere formulation in PBS buffer at 37℃showed preserved activity based on TF-1 cell proliferation assay.This thesis study demonstrated a promising microencapsulation process for formulating structurally delicated protein theraputics.