Study On Electrospun PLGA And PLGA/Hydroxyapatite Nanofibers

Tissue engineering, which uses the principle of engineering and life sciences to create artificial constructs for direct tissue regeneration, has attracted many scientists and surgeons with a hope to treat patients in a minimally invasive and less painful way.Scaffold plays an important role in most tissue engineering strategies. Almost all biodegradable natural biomacromolecules and synthesized polymers biomaterials have been studied as the scaffolding materials. Researchers have developed various technologies to fabricate tissue engineering "hard scaffold", including particle leaching, thermally induced phase separation, solid free-form fabrication, electrospinning and so on. Electrospinning has gained much attention due to its consistency in producing fibers in submicron range. Electrspun three-dimentional fibrous scaffold mimics the structure of natural extracellular matrix (ECM) and favors cell adherence and proliferation. By special material design, multicomponent fibers or oriented fibers can be fabricated, which may introduce signals for cell growth and differentiation. So far, electrospun fibrous scaffolds have been used for constructing of many tissues in the tissue engineering way.In recent years, tissue engineered bone regeneration recieved more interest. There are three key factors in bone tissue engineering: scaffold, growth factors and cells. For scaffolding matierials, both bioactive ceramics and polymer materials have their limits. A strategy is to introduce bioactive ceramics into polymer matrics, which will combine the processibility of polymer and the mechanical strength of ceramics. Meanwhile, bioactive ceramics will enhance the bioactivity and osteoconductivity of the matrics.In this work, we firstly studied the influence of experimental parameters and solution properties on the electrospinning progress and morphology of the resulted fibers. Electon scanning microscopy (SEM) images showed the morphological change of electrospun products with variations of solution concentration, solvent volatility, applied voltage, solution flow rate, nozzle-collection distance and environmenttemperature. Dynamical mechanical analysis (DMA) revealed that the initiating Storage Modulus of the fiber mats decreased with an increase of the average fiber diameters. In degradation experiment, the weight of the fiber mats lost quickly in the first week, then leveled off. After 7 weeks, the degradation rate speeded up again. At the same period, the material volume shrinked a lot.After understanding of the influnce of electrospinning parameters, we introduced hydroxyapatite particles (HAp) and acicular hydroapatite (aHA) into the PLGA matrix. Transmission electron microscopy (TEM) result indicated that aHA dispersed better in PLGA fibers than HAp. DMA curve revealed that the glass transition temperature (Tg) of the composites increased with the addition of HAp or aHA, and the composites became harder compared with the pure PLGA fiber mats. In degradation experiment, the composites shrinked more than the PLGA fiber mats. The PLGA/aHA composites degradated more quickly.Furthermore, human bone marrow mesenchymal stem cells (MSCs) were seeded on both the composite scaffolds and the PLGA fiber mats, and cultured for one week. SEM images indicated that MSCs adhered well on the composite scaffolds and maintained their phenotype. Cell secreties were found on the cell surface. All these rusults suggest that the PLGA/HA composites have potential applications in bone tissue engineering.