Biomedical Engineering Reference
In-Depth Information
Table 22.1
Examples of FDA approved growth factors that can be delivered by nanocarriers
Commercial
Name
Name
Company
Disease and treatment
FDA approval status
Insulin like growth
factor
Increlex
Tercica
Severe primary IGF-1
deficiency
Approved
Insulin like growth
factor
Iplex
Insmed
-
Approved in 2005
and with drawn in
2007
PDGF-BB
(becaplermin)
REGRANEX
Healthpoint
Biotherapeutics
Neuropathic diabetic
ulcers
-
Bone graft consists
of a genetically
engineered human
protein (rhBMP-2)
InFUSE™
Medtronic Sofamor
Danek
Lumbar tapered fusion
device
Approved
BMP-7
OP-1
Stryker
Treatment of long-bone
nonunion fractures
-
Platelet-derived
growth factor
GEM 21S®
Osteohealth
Periodontally related
bone defects
Approved in 2008
of efficient targeting of therapeutic agents with controllable concentration at the appro-
priate time and site [26, 27].
Growth factors are soluble polypeptides that initiate intercellular signals to regulate cell
functions such as proliferation or differentiation. Due to the short biological half-life and
nonspecific distribution, these molecules can be delivered to the site of injuries via nanopar-
ticles as molecular carriers to enhance the efficacy and retention effect [28]. In order to
achieve the specific and accurate identification of target sites for appropriate delivery,
surface modification of carriers is suggested. However, several limitations including insuffi-
cient purification, costly preparation, and risk of adverse immune reaction have restricted
the clinical investigations on biological recognition molecules. For this reason, some
researchers have probed the physical variables (such as size or geometry) instead of chemical
modifications to improve the degree of specific targeting [29].
The nanosized carriers are categorized from different points of view, such as material type,
structure or application. Some important examples of nano delivery systems are highlighted
in Figure 22.2. The characteristics of nanostructures are critical for regulating cytotoxicity or
cell function. For example, investigation on inorganic structures with different dimensions
showed that regulatory procedures require extra attention when the size falls below 30 nm [30].
Figure 22.3 shows the developmental stages of nanomedicine from beginning to commercial-
ization. Current application of nanotechnology in medicine is categorized according to diag-
nostics or therapy. However, it has been predicted that “nanomachines” with the capability of
combined therapy and diagnostics (theranostics) in human beings will emerge in future [31].
Nanocarriers
Liposomes
A liposome is an artificially constructed spherical vesicle (tiny bubble) composed of a phos-
pholipid bilayer, which can enhance the pharmacokinetics and biodistributions of drugs
or growth factors [32, 33]. Tanaka
et al
. reported that injection of magnetic liposomal
