Degradation And Drug Release Behaviors Of PLGA And PLGA/β-TCP Porous Scaffolds Under Dynamic And Static Conditions

As one of three factors in bone tissue engineering, a porous scaffold is often used as a template to guide the differentiation of cells. Furthermore, a scaffold containing bioactive factors plays a special important role in successful repair and regeneration of the bone.In this study, porous poly(lactide-co-glycolide) (PLGA) and PLGA/β-tricalcium phosphate (β-TCP) scaffolds were prepared by thermally induced phase separation and porogen leaching. The porosity of the scaffolds was mainly controlled by the content of porogen, and the morphology was primarily influenced by the freezing temperature and the polymer solution concentration. The compressive properties decreased with increasing the porogen content, decreasing the freezing temperature and diluting the polymer solution concentration. The degradation behaviors of PLGA and PLGA/β-TCP scaffolds were investigated under dynamic condition (cyclic loading) and static condition (water shaking bath), and it was found that cyclic loading could indeed accelerate the degradation rate of the scaffold. The degradation behavior of PLGA scaffolds under dynamic condition showed a three stage degradation model. The viability of osteoblasts cultured on both PLGA and PLGA/β-TCP scaffolds showed a drop tendency with the degradation time of the scaffolds.Bovine serum albumin (BSA) and vitamin C (Vc), as model drugs, were loaded into poly(ethylene glycol)-b-poly(L-lactide) (PELA) microspheres through the method of double emulsion/solvent evaporation. BSA and Vc-loaded PELA microspheres were incorporated into the PLGA scaffolds by using post-seeding method. The release behavior of BSA and Vc from the microspheres incorporated PLGA scaffold under dynamic and static condition was studied. The results showed that comparing with the drug release from PELA microspheres, the drug release from the microspheres incorporated PLGA scaffold showed a lower release rate and a prolonged release time. And the cyclic loading could speed up the release of the drugs from the scaffold. Meanwhile, Vc with low molecular mass showed higher release rate than BSA from both PELA microspheres and PLGA scaffold.Dexamethasone (Dex) and BSA contained PLGA microspheres were prepared by spray drying and double emulsion/solvent evaporation respectively. The effect of initiator, molar ratio of lactic acid (LA) and glycolic acid (GA) and relative molecular mass on the drug release rate was investigated. The release behaviors of Dex and BSA from these microspheres were studied. Selected Dex-loaded and BSA-loaded PLGA microspheres with varied release rate were incorporated into PLGA/β-TCP scaffolds. The in vitro release study indicated that the introduction of m-poly(ethylene glycol) in PLGA could improve the drug encapsulation efficiency in microspheres and reduce the drug release rate from the microspheres. Microspheres prepared from PLGA with lower GA content and higher relative molecular mass showed a prolonged drug release profile. The controllable release rate and release amount of Dex and BSA from PLGA/β-TCP scaffolds could be achieved by selecting the drug-loaded microspheres within the matrix having different degradation rate.