Sustained-release G-CSF microspheres using a novel solid-in-oil-in-oil-in-water emulsion method

The main treatments for cancers are still chemotherapy and radiotherapy for intermediate-stage cancer and terminal cancer. However, the therapeutic methods often result in a decreased neutrophilic granulocyte count and other side effects. In this study, in order to improve the neutrophilic granulocyte levels in the blood after radiotherapy and chemotherapy, we developed a sustained-release granulocyte colony-stimulating factor (G-CSF) microsphere formulation using a novel solid-in-oil-in-oil-in-water (S/O/O/W) emulsification method.

G-CSF was loaded into dextran nanoparticles by freezing-induced phase separation, and then the G-CSF-loaded nanoparticles were encapsulated into sustained-release poly(lactic-co- glycolic acid) microspheres using S/O/O/W emulsification. The control microspheres were also prepared through W/O/W emulsification. The performance of the two microsphere formulations was investigated both in vitro and in vivo.

The microspheres for the controlled release of G-CSF in a zero-order or near-zero-order pattern were provided for 2 weeks. The in vitro cumulative G-CSF release kept over 90% of its bioactivity, which was proved by a NFS-60 cell line growth assay. The microspheres of the control group fabricated by W/O/W emulsification maintained less then half of its bioactivity. The in vivo efficacy of microspheres made using the S/O/O/W method was higher than those using the W/O/W method.

These results suggested that the microspheres prepared by the S/O/O/W method had increased neutrophil activity compared to those prepared by W/O/W.