title: Self-assembly of nano-hydroxyapatite on multi-walled carbon nanotubes.
abstract: Inspired by self-assembly of nano-hydroxyapatite (nHA) on collagen associated with the 67nm periodic microstructure of collagen, we used multi-walled carbon nanotubes (MWCNTs) with approximately 40nm bamboo periodic microstructure as a template for nHA deposition to form a nHA-MWCNT composite. The assembled apatite was analyzed by transmission electron microscopy and scanning electron microscopy. Defects that were analogous to edge dislocations along the carbon nanotubes' multi-walled surfaces were the nucleation sites for nHA after these defects had been functionalized principally into carboxylic groups. Spindle-shaped units consisting of an assembly of near parallel, fibril-like nHA polycrystals were formed and oriented at a certain angle to the long axis of the carbon nanotubes, unlike nHA-collagen in which the nHA is oriented along the longitudinal axis of the collagen molecule. One possible explanation for this difference is that there are more bonds for calcium chelation (-COOH, >CO) on the collagen fibril surface than on the surface of MWCNTs. Spindle-shaped units that are detached from the MWCNT template are able to maintain the ordered parallel structure of the nHA polycrystal fibril. We have thus created a self-assembled hydroxyapatite on MWCNTs.
authors.affiliation: Nanoscience and Nanotechnology Initiative, Division of Bioengineering, Faculty of Engineering, National University of Singapore, Singapore 117576, Singapore. bieliaos@nus.edu.sg
authors.forename: Susan
authors.initials: S
authors.lastname: Liao
authors.forename: Guofu
authors.initials: G
authors.lastname: Xu
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Fumio
authors.initials: F
authors.lastname: Watari
authors.forename: Fuzhai
authors.initials: F
authors.lastname: Cui
authors.forename: Seeram
authors.initials: S
authors.lastname: Ramakrishna
authors.forename: Casey K
authors.initials: CK
authors.lastname: Chan
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D018929:Cell Culture Techniques / Q000379:methods; D002478:Cells, Cultured; D003460:Crystallization / Q000379:methods*; D017886:Durapatite / Q000737:chemistry*; D008422:Materials Testing; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D023822:Tissue Engineering / Q000379:methods
chemical_list: D001672:Biocompatible Materials; D037742:Nanotubes, Carbon; D017886:Durapatite