UV-Assisted Grafting Carbon Nanotubes And Their Biomineralization On Different Fuctional Groups

Hydroxyapatite(HA), as the major component of human bone and teeth, is widely used for hard tissue repairing. But its poor fracture toughness and wear resistance become its major shortcomings. Compositing with other renforcement materials may be the best way to solve this problem. Carbon nanotubes(CNTs) could be the ideal candidate due to their good mechanical properties and biological activity. CNTs-HA composite material can combinate advantages of both materials and overcome certain disadvantages, so as to becomes an excellent biological materials.The research is to prepare CNTs-HA component by mineralizing grafted modifed CNTs.and compare the differences of biomineralization processes inducing by different functional groups.To investigate the effects of organic groups such as carbonyl, acylamino and hydroxyl on the nucleation and growth of CaP compounds, multi-walled carbon nanotubes (MWNTs) were modified with different acrylate monomers and subjected to mineralization using simulated body fluid (SBF). Briefly, monomers (acrylic acid, acrylamide or hydroxyethyle methylacrylate) were photo-polymerized and grafted onto acid-treated MWNTs, followed by being immersed in1.5times SBF at36.5℃, pH=7.4for different time points. The deposited mineralites were characterized systematically by using various techniques, including SEM, TEM, XRD, EDX and FT-IR, etc. The results reveal that the nucleation and growth of Ca/P minerals depend remarkably on the surface features of the modified MWNTs, as well as the soaking time. The carboxyl group can induce the nucleation the fastest and demonstrate the highest Ca/P ratio, followed by the acylamino group and the hydroxyl group. In the three cases, however, the morphology of the deposited mineralites changes in a similar way through time. The initial mineralite spheres originating from the surface of modified MWNTs gradually grow into relatively big ones with flaky-like structure on surface, which enwrap MWNTs in reverse at the later stage. The flaky-like structure of the final mineralites indicates the formation of CDHA.Calcification is another way to invest the difference of HA minerals induced by three different functional groups. Briefly, the products of mineralization from three different UV-grafted carbon nanotubes were calcined in muffle furnace at1000℃for1hr. Then the samples were characterized by SEM and XRD. The result revealed, the crystal structure induced by acylamino group was the closest to the hexagonal prism structure of natural hydroxyapatite.