Preparation And Release Behavior Of PLGA Scaffolds Encapsulating Proteins Loaded In Chitosan Microspheres

[Objective] Exogenous growth factors have a short half-life period, which are diluted and metabolized in vivo. The study was designed to prepare delivery scaffolds with suitable porosity, degradation, mechanical strength, and have an excellent releasing efficiency for growth factors.[Methods] Chitosan microspheres (CMs) was formed by an emulsionionic crossing-linking method. Bovine serum album (BSA) was selected as a model protein. Using ice particulates as porogen, composite scaffolds were prepared with CMs/nano-hydroxy-apatite/poly (lactic-co-glycolic acid) (PLGA) by freeze-drying. The characteristic and morphology of the composite were observed by scanning electron microscope (SEM), later particle size analyzer, mercury porosimeter and universal testing machine. Release behavior of BSA was investigated in vitro.[Results] The CMs were spherical in shape with a regular surface. The diameters of the CMs were in the range of 20-40μm. The encapsulation efficiency of the CMs was 86.5%, and the loading capacity was 0.8%. With the increase of initial BSA dosage, the loading capacity increased to 2.6%, while the encapsulation efficiency decreased to 74.1%. The CMs can be uniformly distributed in the composite. The pore diameter of the composite scaffolds was about 100-400μm, the porosity was over 80%, and the compressive strength was about 1.6-2.4 MPa. The cumulative degradation was 26.5% at 10 weeks. The cumulative release of BSA from PLGA scaffolds was above 85% at 36 hours, which from CMs was 33.6% on 10 days, while that from CMs/nHA/PLGA scaffolds was 81.5% on 36 days. There aren't significant effects on porosity, degradation and mechanical strength of the composite scaffold, P>0.05. The control-release effect of CMs/nHA/PLGA is significantly better than that of nHA/PLGA scaffold or CMs, P<0.05.[Conclusion] The nHA/PLGA scaffolds encapsulating chitosan microspheres are proved to have an excellent release function for protein drugs with suitable compressive strength and degradation. The CMs/nHA/PLGA scaffolds would be used as delivery system and tissue engineering scaffolds.