Biomedical Engineering Reference
In-Depth Information
6.5.2.1 HA Nanomaterials
One example of a bionanocomposite that has been widely used as a biocom-
patible ceramic material in many areas of medicine, particularly for contact
with bone tissue owing to its resemblance to mineral bone is HA (Ca
10
(PO
4
)
6
(OH)
2
))
260
which is the major mineral component(69% weight) of human hard
tissues. HA in natural or synthetic form possesses excellent biocompatibility
with bones, teeth, skin, and muscles, both in vitro and in vivo. It is biocompat-
ible, promotes bone growth, and hardens in situ with Ca/P ratio at 1.5-1.67 that
is within the range known to promote bone regeneration.
127
These properties
of HA make it widely used for hard tissue repair in orthopedic surgery and
dentistry.
13,10
Inorganic and organic composites mimic the composite nature of
real bone that combines the toughness of the polymer phase with the compres-
sive strength of the inorganic component to generate bioactive materials that
has improved mechanical properties and degradation profiles.
127
In these com-
posites, the alkalinity of the inorganic particle (such as HA) neutralizes acidic
autocatalytic degradation of polymers such as PLA, exploiting a bioactive func-
tion.
261
To date, calcium phosphate biomaterials have been widely used in the
form of powders, granules, dense porous blocks, and various composites.
127
Studies showed that better osteoconductivity would be achieved if synthetic
HA could resemble bone minerals in composition, size, and morphology.
262
Furthermore, nanosized HA may have other special properties due to its small
size and huge specific surface area resulting in significant increase in protein
adsorption and osteoblast adhesion on the nanosized ceramic materials com-
pared with traditional microsized ceramic materials.
262,263
Studies have shown
that n-HAP particles influenced the conformation of adsorbed vitronectin (a
linear protein 15 nm in length that mediates osteoblast adhesion).
162,264
Poly-
saccharide and polypeptide matrices have been used with HA nanoparticles in
hybrid composites
265
that are conducive to the attachment, growth, and prolifer-
ation of human osteoblast cells. For example, collagen-based polypeptidic gela-
tin is currently being used in wound dressings and pharmaceutical adhesives in
clinics.
266
This can be combined with the bioactivity and osteoconductivity of
HA to generate potential engineering biomaterials.
6.5.2.2 Carbon Nanostructures
Carbon nanostructures such as fullerenes, CNTs, CNFs, graphene, and a wide
variety of related forms
267
are attractive nanomaterials for the development of
innovative devices in the form of composites, sensors, and nanoscale electronic
devices.
268,269
Polymers that incorporate carbon nanostructures have been stud-
ied for different of biomedical uses.
180,270,226,223
CNTs can provide the needed
structural reinforcement for biomedical scaffolds.
127
Combining a small frac-
tion of CNTs with a polymer provides significant improvements in the compos-
ite mechanical strength (owing to the CNTs mechanical strength) making them
suitable candidates for novel polymer composites.
271,272
The physical properties
