Biomedical Engineering Reference
In-Depth Information
Two-week soaking of MWCNTs in simulated body luid results
in the formation of nanocrystalline hydroxyapatite [2]. Carbon
nanotubes functionalized with phosphate groups enhance their
biomineralization coatings and form layers of hydroxyapatite
crystals, because of ionic interactions between the negatively
charged functional groups and the positively charged calcium ions.
Functionalized carbon nanotubes can provide additional capabilities
for tissue engineering. Direct crystallization of hydroxyapatite on
carbon nanotubes results in a thickness of 3 mm after 14 days of
mineralization [65]. Carbon nanotubes are able to provide the initial
structural reinforcement needed for newly created tissue scaffolds.
Carbon nanotube coatings and nanocomposites have been
successfully applied as substrates for biomineralization, growth,
proliferation, and normal functions of osteoblast-like and osteoblast
cells [52]. These properties depend upon the type of carbon nanotubes,
the chemical nature of treatment , and the composite composition
[52]. Application of an electrical current to the conductive carbon
nanotubes stimulates increases in the proliferation of the osteoblasts,
the extracellular concentration of calcium, and the up-regulation of
mRNA expression for collagen type-I [53].
Chlopek
et al
. [12] show good biocompatibility of the nanotubes,
which is similar to that of polysulfone. Nanotubes show good
cellular biocompatibility, because of high level of viability of the cells
in contact with the nanotubes and unchanged level of osteocalcin
released from osteoblasts. Chlopek
et al
. found a slight increase of
collagen formation induced on nanotubes by both ibroblasts and
osteoblasts, which may be signiicant for applications as substrates
for the tissue regeneration [12].
Carbon nanotubes can be functionalized with drugs and
biomolecules and proteins, for applications in drug delivery and
antibiotics [14, 52]. Liu
et al
. investigated decoration of carbon
nanotubes with chitosan [41]; the decoration of CNT with CHIT
creates new CHIT-CNT nanomaterials. They have applied a non-
destroyable surface decoration of carbon nanotubes with chitosan
biopolymer via a controlled surface-deposition and cross-linking
process. The method utilizes the emulsifying capacity of chitosan, a
completely different water-solubility of chitosan in acidic and basic
solutions, and the cross-linking reaction among chitosan polymers
[41]. The method consists of the following steps:
(i) Dispersion of MWCNTs in chitosan acetic acid solution is
carried out, and during the stirring, the CHIT-CNT blend the
