Biomedical Engineering Reference
In-Depth Information
as for drug delivery purposes. The nano-sized β-TCP exhibits a
significant biological affinity and activity and responds very well to
the physiological environment. A lot of research is expected for much
enhanced applications of the nanodimensional and nanocrystalline
calcium orthophosphates for both drug delivery systems and as
resorbable scaffolds that can be replaced by the endogenous hard
tissues with the passage of time [122, 672].
Although the nanostructured biomaterials may have many
potential advantages in the context of promoting bone cell
responses [455-457, 588], it is important to remember that studies
on nanophase materials have only just begun; there are still many
other issues regarding human health that must be answered. Since
particles of very low size have higher reactivity and effectiveness,
a rapid technical development of nanometer-scaled particles in the
biomedical field leads to concerns regarding the unknown risks
of such materials [665, 666]. These nano-sized particles might
induce inflammatory reactions, cytotoxicity, oxidative stresses or
thrombogenesis when injected for drug delivery purposes. Namely,
nano-sized particles may enter the human body through pores
and may accumulate in the cells of the respiratory or other organ
systems (when becoming dislodged through wear debris) and the
health effects are yet to be largely known. This could happen during
commercial-scale processing of the nano-sized particles as well as
using these materials as implants [673]. Besides, nano-sized particles
might be the objects whose existence has not been assumed by living
body defense system [18, 119, 120]. Up to now, only a small number of
short-term and small-scale health effects of single nanodimensional
materials have been examined in toxicological studies, usually
of the lungs [666]. Therefore, prior to clinical applications, any
toxicity concerns of the nanophase materials [674-679] need to be
overcome.
In summary, despite the challenges that lie ahead, significant
evidences now exist elucidating that nanophase biomaterials
represent an important growing area of research that may improve
bonding between the implants and the surrounding tissues. It
has proven to be a versatile approach that can increase bone cell
functions on a wide range of orthopedic implant chemistries. Even if
the nanodimensional and nanocrystalline calcium orthophosphates
do not provide the ultimate answer for increasing bone cell responses
(due to some potential problems as mentioned above), researchers
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