Controlled Release of Growth Factors from Microsphere Scaffolds for Osteogenesis

Abstract

Large bone defects present a major challenge to orthopaedic surgeons. Tissue engineering technology may provide a potential strategy to repair such defects, which involves the implantation of scaffold constructs typically loaded with cells and growth factors. It is expected that such growth factors loaded scaffolds can produce optimal microenvironments for the differentiation of seeded cells. The purpose of this project was to construct a dual growth factor release system in vitro using gelatin hydrogel and microspheres (MSs) to carry and deliver two growth factors, which have different effects on the growth and development of bone marrow derived mesenchymal stem cells (BMSCs) as well as bone tissues. The experimental studies of this project were divided into three sections as detailed below. In the first section of this study, both the conventional double emulsion technique and the electrospraying technology were combined with the thermally induced phase separation (TIPS) approach to prepare the bovine serum albumin (BSA)-loaded poly (lactic-co-glycolic acid) (PLGA) porous MSs. The particle size, surface morphology and the internal porous structure of the MSs were characterised using scanning electron microscopy (SEM). The release profile and the encapsulation efficiency of the BSA as a model protein in the PLGA MSs were established. The results showed that the novel electrosprayed MSs had uniform particle sizes between 400-600mm, many well-connected internal pores, high efficiencies of encapsulation and loading of the model protein, and a higher porosity than those MSs derived from the conventional double-emulsion method. Thus, the combination of the electrospraying technique with a low temperature freezing had proved to be a suitable method to produce polymer MSs for the controlled-release of the loaded-protein.