Magnetic Nano-fiber Composites, And Osteogenesis

Bone defects and loss of function caused by trauma, infection, tumor, congenital malformations often need repair by implant replacement. The procedures utilize autografts, allografts or metallic and ceramic implants to correct the bone defect. Each of these options has its own drawbacks such as donor site morbidity, pathogen transmission, and mismatching material properties with the native bone respectively. As an alternative to these procedures, tissue engineering has emerged to create de novo tissue by growing cells on three-dimensional (3D) scaffolding. Ideally, this scaffolding should recapitulate the key structural and biochemical signals of the tissue's natural extracellular matrix (ECM), which is primarily composed of type I collagen in bone.In natural tissues, cells are surrounded by a complex mixing of nonliving materials that make up the ECM. It is composed of complex mixtures of protein and proteoglycans, made up of nanofibers. And those fibers organized to form a 3D network with interconnected pores. ECM takes an important role in cell growth, migration and differentiation. Most components of the natural ECM have structural features in the nanometer dimensions, and the organization of cells and the corresponding tissue properties are found to be highly dependent on the architecture of the ECM. Several techniques have been developed to fabricate biomimetic nanofibrous matrix by using different synthetic and natural materials.Electrospinning is one of the most utilized methods, which is a unique process for producing fibers with nanoscale diameters through the action of a high electric field. The structures generated by electrospining contain nanoscale fibers with microscale-interconnected pores, resembling the topographic features of the ECM. Recently, fibrous scaffolds fabricated by electrospinning have been used for tissue engineering. A broad range of materials, from natural polymers and recombinant proteins, to synthetic polymers, have been processed into fibrous and porous scaffolds for studies in tissue engineering biomaterials.Polylactic acid (PLA), which is well biocompatible and biodegradable, can meet the requirements of scaffold materials for bone and cartilage tissue regeneration and repair. Hydroxyapatite (HA), which is a natural main component of bone extracellular matrix, has good properties of bone induction and bone adhesion. Magnetic nanoparticles (M-NP), because of its unique superparamagnetic, enable cells in a multiple small magnetic field, and regulate cells growth and behavior.In this work, a paramagnetic nanofibrous composite film was fabricated with poly lactide, hydroxyapatite andγ-Fe2O3-NP nanoparticles using electrospinning technique. We detected the secretion of alkaline phosphatase of the MC3T3-E1 osteoblast, observed the mineralization by scanning electron microscope, and conduct animal experiments to explore the magnetic properties of nano-fiber composite for bone damage repairment in vivo.Experimental results show that the non-woven magnetic material has a biomimetic scaffold network structure with fiber diameter of 100-600nm. The composite film can significantly enhance the proliferation, differentiation, ECM secretion and biomineralisation in the osteogenesis of the pre-osteoblast cells under a static magnetic field, which offers a potential scaffold for bone tissue engineering and bone regeneration therapy. And under a static magnetic field, the non-woven magnetic material can significantly promote bone repair and regeneration in animals.It is clear that cells would respond to nanometric scale surface features, therefore it is possible to induce certain responses of cells by fabricating substrates with combined micro-nano patterns. Herein, transparent polyurethane films with micro-nano groove patterns were prepared by solvent-casting from a template. Mouse fibroblast cells (3T3-L1) were seeded on the patterning films and cultivated for at least one week. Cell morphologies and cytoskeleton protein expression in the fibroblasts were observed with optical microscope and confocal laser scanning microscopy. Cells adhesion and proliferation were examined using MTS assay. Experimental results showed that the micro-nano groove pattern significantly enhanced the adhesion and proliferation of fibroblasts. The micro-nano groove pattern also showed effects in inducing cytoskeleton rearrangement as well as promoting actin and tubulin expression.