Assisted deposition of nano-hydroxyapatite onto exfoliated carbon nanotube oxide scaffolds

Electrodeposited nano-hydroxyapatite (nHAp) is more similar to biological apatite in terms of microstructure
and dimension than apatites prepared by other processes. Reinforcement with carbon nanotubes
(CNTs) enhances its mechanical properties and increases adhesion of osteoblasts. Here, we carefully
studied nHAp deposited onto vertically aligned multi-walled CNT (VAMWCNT) scaffolds by electrodeposition
and soaking in a simulated body fluid (SBF). VAMWCNTs are porous biocompatible scaffolds with
nanometric porosity and exceptional mechanical and chemical properties. The VAMWCNT films were prepared
on a Ti substrate by a microwave plasma chemical vapour deposition method, and then oxidized
and exfoliated by oxygen plasma etching (OPE) to produce graphene oxide (GO) at the VAMWCNT tips.
The attachment of oxygen functional groups was found to be crucial for nHAp nucleation during electrodeposition.
A thin layer of plate-like and needle-like nHAp with high crystallinity was formed without any
need for thermal treatment. This composite (henceforth referred to as nHAp–VAMWCNT–GO) served as
the scaffold for in vitro biomineralization when soaked in the SBF, resulting in the formation of both carbonate-rich
and carbonate-poor globular-like nHAp. Different steps in the deposition of biological apatite
onto VAMWCNT–GO and during the short-term biomineralization process were analysed. Due to their
unique structure and properties, such nano-bio-composites may become useful in accelerating in vivo
bone regeneration processes.