Prepatation And Properties Of Electrospun Nanofibrous Scaffolds For Bone Regeneration

With the development of tissue engineering and regenerative medicine, biomaterial scaffolds play more and more important role in the clinical repair and therapy of bone loss or damage.Recently,the study of bone tissue engineering scaffolds has been attracted much attention.In particular,incorporation of bioactive ceramics into polymer matrix is assumed to mimic the composition of natural bone extracellular matrix(ECM),thus can enhance cell growth and response.Meanwhile, highly porous biomimetic nanofibrous structure may bring additional stimulus to the cultured cells and finally induce bone formation.Therefore,the design and preparation of nanofibrous polymer/bioactive ceramics composite scaffold is one of the supreme methods for obtaining ideal bone tissue engineering scaffolds.Based on the previous research work in our laboratory, poly(lactide-co-glycolide)/nano-hydroxyapatite(PLGA/HA) composite scaffold was firstly studied.The composites were prepared by electrospinning of PLGA solution having both synthesized hydroxyapatite particles(HAp) or commercially acicular hydroapatite(aHA).The electrospun composite scaffold showed a randomly interconnected and highly porous structure composed of continuous bead-free nonwoven nanofibers.Both HAp and aHA concentration of 5wt%could disperse well in the PLGA fiber matrix.In vitro mineralization in a 5×simulated body fluid(SBF) revealed that the PLGA/HAp nanofibrous scaffold had a stronger biomineralization ability than the PLGA/aHA and control PLGA scaffolds.In vitro culture of neonatal mouse calvaria-derived MC3T3-E1 osteoblasts reveals that all the samples could support cell proliferation and showed increase of viability,but the cells cultured on the PLGA/HAp nanofibers showed more spreading morphology.Despite the similar level of the cell viability and cell number at each time interval,the alkaline phosphatase(ALP) secretion was significantly enhanced on the PLGA/HAp scaffolds, indicating the higher bioactivity of the as-prepared nano-HAp and the success of the present method for preparing biomimetic scaffold for bone tissue engineering.By simulating the self-assembly process of collagen nanofibers and hydroxyapatite particles in the formation of natural bone,PLGA/collagen/HA ternary nanofibrous composite scaffolds were further fabricated.Using plasma treatment to initially improve the hydrophilicity of PLGA electrospun fibers, collagen molecules could be easily coated on the surface.The modified fibers were successively immersed into 5×SBF to induce mineral deposition.The mineral particles were firstly nucleated on the surface of single fibers and gradually grown up to velvetball-like microparticles,even covering the whole surface of the nanofibrous scaffolds.Both chemical analysis by energy-dispersive X-ray spectrum(EDS) and fourier transform infrared spectroscopy(FTIR),and crystal determination by X-ray diffractometer(XRD) and transmission electron microscopy(TEM) showed that the minerals were aggregation composited of tiny HA nanoparticles.The mechanical properties of the nanofibers were enhanced after collagen coating and HA deposition. All the control PLGA,PLGA/collagen and PLGA/collagen/HA nanofibrous scaffolds could maintain the viability of MC3T3-E1 osteoblasts.However,the latter two showed better ability to induce cell spreading.Particularly,cells on the PLGA/collagen/HA composite scaffolds secreted more ALP after 14d culture, indicating the higher bioactivity for the growth and phenotype expression of the cultured osteoblasts.The high biomimetic PLGA/collagen/HA nanofibrous composite scaffold are expected to be an ideal bioactive candidate for bone regeneration.To overcome the problem of small pore size of the dense nanofibrous scaffolds, different methods were tried to explore the feasibility of preparing dual-porous nanofibers.Studies found that compounding sodium chloride(NaCl) particles with PLGA fibers during the electrospinning process could be a useful way.After particle leaching,nanofibrous scaffolds with certain larger pores were prepared.Still,by collagen modification and HA deposition,dual-porous PLGA/collagen/HA composite scaffolds were finally obtained.HA could be mineralized on both the surface of the fibers and inside the large holes.It is expected that such nanofibrous composite scaffolds with dual-porosity could not only enhance the cell growth but also improve the cell infiltration into the scaffolds,thus have the potential to be ultimate applied as ideal scaffolds for bone tissue engineering and regenerative medicine.