PAN-Based Hybrid Carbon Nanofibers And Its Biological Characteristics

Carbon nanofibers (CNFs) show good mechanical properties, chemical stability, high aspect ratio and easy surface functionalized capability to be decorated with more biocompatible hydrophilic groups, which are concerned by more and more researchers. And the CNFs prepared by electrospinning-carbonization which mimic the structure of natural extracellular matrix have attracted considerable attention for both fundamental scientific understanding and their potential biomedical applications. In order to form sufficient bonding between CNFs and juxtaposed bone tissue and to minimize motion-induced damage to surrounding tissue in situ, combination of CNFs with biomaterials is a very effective approach. In this study, a new combination of electrospinning, sol-gel and in-situ sintering was used to prepare the PAN-based hybrid carbon nanofibers. To evaluate the feasibility and superiority of the new type of biomaterials for clinical use, the material composition, phase structure, cytotoxicity, biocompatibility and bioactivity were all studied systematically.Firstly, the electrospinning of PAN nanofibers were optimized by using mixture solutions. As a result, not only the fiber diameters were narrower obviously, but also the process stability was improved. After hot stretching treatment, the fiber diameters were reduced and the fiber gaps become smaller while the maximum tensile strength reached 302 MPa. Secondly,β-tricalcium phosphate (β-TCP) is a biodegradable bio-ceramic materials for bone repair, which can provide the necessary calcium and phosphate ions. By controlling the pH value of hydrolysis system, adjusting the catalyst and sol-sintering temperature, high purity and high crystallinity ofβ-TCP crystals with triethyl phosphate (TEP) and calcium nitrate (CN) as the phosphorus and calcium source were prepared. Thirdly, PAN/TEP-CN composite nanofibers were prepared by electrospinning. After the hot strenching treatment, stabilization and carbonization of the PAN/TEP-CN composite nanofibers, a type of nanofibers with biological properties provided byβ-TCP and the structural properties provided by CNFs was fabricated. And the morphology and biological characteristics of the composite nanofibers with different sol volumes were studied.The results show that theβ-TCP nanoparticles are mainly on the surface of the CNFs when the composite fibers were prepared at low sol volume, and the diameter of the nanoparticles is 20-30 nm. TEM analysis shows that the nanoparticles are maily located inside the nanofiber when prepared at high sol volume, and finally form a bamboo-like structure. The accelerated degradation of composite nanofibers with high sol volume was studied. The long-continued nanofibers can be effectively degraded into small CNFs with aspect ratio due to the degradation of (3-TCP nanoparticles.The biocompatibility test was carried on the above-mentioned composite nanofibrous scaffolds, including cytotoxicity test (MTT test) and human periodontal ligament cells (hPDLCs) in vitro co-culture experiments. MTT test results indicate that the prepared materials have good biocompatibility, and no apparent toxicity. Confocal laser microscope observation shows that the PDLCs adhere favorably onβ-TCP/CNFs membranes with proliferating preferencely along the aligned longitudinal direction of nanofibers. Scanning electron microscopy (SEM) shows that the PDLCs were in close combination with materials, and produces large amounts of extracellular matrix.It is generally believed that bioglass is a widely-used bone repair material, which has shown an excellent behavior when it is in contact with physiological fluids. In addition, bioglass is the only one, which can bond to both hard and soft tissue. In this study, carbon nanofibers decorated with bioglass nanoparticles have been prepared by sintering electrospun polyacrylonitrile fibers with calcium nitrate tetrahydrate as the calcium source, tetraethoxysilane (TEOS) as the silica source and triethyl phosphate as the phosphorus source. The SEM reveals that the average diameter of the nanofibers is 360 nm, and the diameter of nanoparticles on the surface of the composite nanofibers is about 20 nm. The results of mineralization in five-timed simulated body fluid (5SBF) characterized by XRD, FTIR and EDX analysis indicate that this kind of hybrid nanofibers possesses good bioactivity. After immersion in 5SBF for 6 h, granular crystals grow from the bioglass nanoparticles which are on the surface of the nanofiber. With the mineralization time extending, the granular crystals become more and more spherical, and after 30 h, the mineral layer are thicker than 600 nm, completely covering the surface of the composite nanofibers. The results show that the obtained flower-like crystals are carbonated hydroxyapatite.Therefore, theβ-TCP or bioglass decorated CNF nanofibrous materials with good biocompatibility and structural properties can be used as promising biomaterials for guide tissue/bone regeneration.