Preparation, Morphological Evolution And Bioactive Properties Of PCNF/BG

With the continuous development of tissue engineering, carbon nanofibers (CNFs) has become a hot topic in the field of orthopedic materials. In our previous work, bioactive glass (BG) was loaded inside and outside of the CNFs to prepare hybrid nanomaterials with good osteocompatibility and mechanical performance. What’s more, a large number of studies have shown that the release rate of the BG has a direct relation with materials’structure, such as the specific surface area. In this paper, BG decorated nanoporous composite carbon nanofibers (PCNF/BG) were prepared by the blending electrospinning of polyacrylonitrile (PAN) and polymeric porogen with addition of sol-gel precursors of BG, followed by high temperature thermal treatment. Then the morphological evolution and bioactive properties of PCNF/BG were systematically studied, which can provide basic data and theoretical guidance for the research of bioactive composite carbon nanofibers.Polyvinyl Pyrrolidone (PVP), polyethylene glycol (PEG), polymethylmethacrylate (PMMA) were selected as porogen, and the porous structure was characterized by SEM. The results indicated that PMMA showed the best performance of generating porous structure inside and outside of the CNFs. There were only a few pores inside the CNFs with PEG as the porogen. However, CNFs didn’t show any hint of porous structure with PVP as the porogen. The phase contrast microscope showed the system of PAN/PMMA had the most obvious phase separation, as a result the best porous structure was generated.The morphological evolution of PCNF/BG with different PMMA content was characterized by SEM, TEM, TGA and BET. The results indicated that PCNF/BG-1/0 composites showing no hint of porous structure. With the induction of PMMA, porous structure was distinctly detected in PCNF/BG-2/1 and PCNF/BG-4/3. In addition, as the PMMA content increasing, PCNF/BG-4/3 displayed apparently larger pore size and higher porosity than PCNF/BG-2/1, and continuous slitlike nanoporous structure were even detected on CNFs’ surface of PCNF/BG-4/3. Therefore, the specific surface area and surface roughness of PCNF/BG-4/3 were the maximum among PCNF/BG.To investigate the effect of porous microstructure on biomineralization, the experiment was achieved by immersing PCNF/BG composites in 1.5 times simulated body fluid (1.5SBF) for various time. The results showed that minerals deposited continuously on the surfaces of PCNF/BG-1/0, PCNF/BG-2/1 and PCNF/BG-4/3 with the biomineralization proceeding, but the amounts of depositions differed between them. The amount of minerals could be seen in the order of PCNF/BG-4/3> PCNF/BG-2/1> PCNF/BG-1/0. The minerals was confirmed to be carbonated hydroxyapatite (HCA) according to the XRD, FTIR and EDS analysis. The phenomenon was resulted from a series of ion change between BG and SBF, which can promote the nucleation and subsequent growth of HA. Compared with PCNF/BG-1/0, the nanoporous structure of PCNF/BG-2/1 and PCNF/BG-4/3 could provide larger surface area, which would facilitate faster ion change of BG nanoparticles, especially PCNF/BG-4/3 with the largest pore volume and surface area.In order to investigate the effect of porous microstructure on biocompatibility and osteoconduction, the osteoblasts were seeded on PCNF/BG composites and cultured for various time. The cell proliferation assay showed that the osteoblasts proliferated well on all samples, which indicated the good biocompatibility of all PCNF/BG composites. Especially PCNF/BG-4/3 showed the best biocompatibility with the highest cell proliferation rates. The cell differentiation assay showed that the osteoblasts’ALP activity of all PCNF/BG composites increased with the prolonged culture time and reached the peak value, then it decreased. In addition, the osteoblasts showed the highest expression in ALP activity on PCNF/BG-4/3. The results indicated all samples had the ability of inducing osteogenic differentiation, especially the PCNF/BG-4/3. The reason was that the osteoblasts preferred to attach on rougher surface. Furthermore, the soluble ions (Ca2+, PO43-, etc.) releasing from BG into the culture medium could promote cell proliferation and differentiation. The porous structure, rougher surface and larger specific surface areas of PCNF/BG-2/1 and PCNF/BG-4/3 could promote cell attachment and accelerate ions release rate, especially PCNF/BG-4/3.