Gongwen Tang

Effect of Cyclic Loading on In Vitro Degradation of Poly(L-lactide-co-glycolide) Scaffolds

The in vitro degradation performance of porous scaffolds is very important in tissue engineering, especially the scaffold implanted in the environment imitating the repaired tissue. In this paper, the effect of cyclic loading on in vitro degradation of porous poly(L-lactide-co-glycolide) (PLGA) scaffolds was studied by incubating the samples in phosphate-buffered saline at 37°C and pH 7.4 under dynamic conditions (cyclic loading) and static conditions (shaking water bath) for 12 weeks. The results showed earlier morphological variations and faster reduction in mass, dimensions and relative molecular mass of the scaffolds under dynamic conditions. Mechanical properties (the compressive modulus and the compressive strength) of the PLGA scaffolds under both conditions tended to increase in the first 3 weeks, but showed a decrease tendency afterward. The scaffolds under dynamic conditions were too brittle to be further characterized after degradation for 6 weeks, while those under static conditions endured degradation until week 8. The degradation mechanism of the PLGA scaffolds under cyclic loading was clearly explained and a three-stage degradation model based on the degradation behaviors of the scaffolds under two conditions was presented.

Controllable dual-release of dexamethasone and bovine serum albumin from PLGA/β-tricalcium phosphate composite scaffolds

Localized dual-drug delivery from biodegradable scaffolds is an important strategy in tissue engineering. In this study, porous poly(L-lactide-co-glycolide) (PLGA)/β-tricalcium phosphate scaffolds containing both dexamethasone (Dex) and bovine serum albumin (BSA) were prepared by incorporating Dex-loaded and BSA-loaded microspheres into the scaffolds. PLGA microspheres containing Dex or BSA were prepared by spray-drying and double emulsion/solvent evaporation, respectively. In vitro release studies indicated that microspheres prepared from PLGA in 3:1 molar ratio of L-lactide/glycolide and 89.5 kDa relative molecular mass showed prolonged release profiles compared with those prepared from PLGA in 1:1 L-lactide/glycolide molar ratio and 30.5 kDa relative molecular mass. Additionally, introduction of poly(ethylene glycol) in the PLGA chain could improve the encapsulation efficiency and reduce the release rate. Based on the above results, controllable dual-release of Dex and BSA with relatively higher or lower release rate was achieved by incorporating Dex-loaded and BSA-loaded microspheres with different release profiles into the PLGA/β-tricalcium phosphate scaffolds.

Preparation of PLGA Scaffolds with Graded Pores by Using a Gelatin-Microsphere Template as Porogen

Abstract Porous scaffolds with graded pores are crucial to osteochondral regeneration. In this study, a technique combining solution casting with gelatin-microsphere template leaching has been developed to produce poly(L-lactide-co-glycolide) (PLGA) scaffolds with graded pores. The traditional emulsification and solvent extraction method was improved by using the gradient ethanol/water solutions to extract water to prepare gelatin microspheres with a smooth surface without the use of any surfactant. Gelatin microspheres with different diameters were in sequence put into a custom-made cylindrical Teflon mold and bonded together to obtain gelatin-microsphere templates. By using the gelatin-microsphere templates as porogen, PLGA scaffolds with graded pore size across the cylindrical axis were prepared. The porosity of the scaffold was as high as 95%. The pore size effect on osteoblasts was studied. The results showed that the graded scaffolds possessed good biocompatibility for osteoblast growth. During the 14 days culture, the cell proliferation of all the three pore layers displayed the trend of increasing. The proliferation rate of the large pore layer was lower than the other two layers. However, the difference of alkaline phosphatase activity on the three pore layers was not statistically significant. We assumed that it was probably because of the hydrophobicity and the short culture time. It was demonstrated that gradient ethanol/water solutions provided a simple way to prepared gelatin microspheres. The graded scaffolds would provide potential application for osteochondral regeneration.

Fibre–Microsphere Membranes with Continuous BMP-2 Gradients with Potential Applications in Interface-tissue Engineering

Functional gradient scaffolds play an important role in interface-tissue engineering, because of the gradual transition of both physical and chemical properties in interface tissues such as bone–cartilage, bone–ligament, and bone–tendon. In this study, a poly(l-lactide-co-glycolide) fibre–microsphere membrane with continuous-gradient bone morphogenic protein-2 (BMP-2) distribution was developed by a combined technique of electrospinning and electrospraying. The fibre–microsphere membrane had a ‘sandwich’ structure, in which the electrosprayed poly(l-lactide-co-glycolide) microspheres loaded with BMP-2 showed a gradient distribution in amount between two pieces of electrospun fibrous membranes. Proliferation of preosteoblast MC3T3-E1 cells cultured on the fibre–microsphere membrane for 21 days demonstrated a bioactivity response to the released amount of BMP-2 in a gradient mode. The study suggested that the technique of electrospinning combined with electrospraying is an effective way to prepare functional gradient membranes with potential applications in bone–interface tissue regeneration.