Biomedical Engineering Reference
In-Depth Information
Table 9.1 Advantages of nanomaterials compared with conventional materials
Small size
(for example, penetrating the blood±brain barrier for drug delivery applications)
[20,21]
Large surface area
(for example, a high density of functional groups can be functionalized with
various biological agents) [6±10]
High surface energy
(for example, improving certain protein adsorption to enhance tissue cell adhesion
and functions) [11±13]
Excellent bio/cytocompatibility and decreased immune responses as
well as inhibit bacteria infection [14±19]
Other unique chemical/physical properties
(for example, superparamagnetic nanoparticles for enhancing magnetic resonance
imaging (MRI)) [6, 22]
traditional micron-structured materials, nanostructured biomaterials are more
reactive to bodily fluids (namely ions and proteins) and can be immobilized on a
high density of functional groups for specific purposes (such as controlled drug
delivery) [6±10]. This is because the larger surface areas and numerous
angstrom/nanometer dimensioned defects of nanostructured biomaterials alter
surface electron distributions to adsorb particular biological agents [11]. Since
proteins are charged, such surface properties of nanostructured biomaterials will
change surface energetics to influence protein interactions that subsequently
mediate cell functions to regenerate tissues. In addition, hydrophilic nano-
structured biomaterials have higher surface energy than corresponding micron-
structured materials. For example, decreasing alumina grain size from 167 to
24 nm, alumina surface hydrophilicity was significantly increased to promote the
adsorption of hydrophilic proteins that enhance osteoblast (bone forming cells)
adhesion [12, 13].
Another novel property of nanostructured biomaterials is that they (in some
cases) minimize immune cell recognition. For example, decreased macrophage
functions were observed on aligned regions of carbon nanotubes compared with
conventional polycarbonate urethane [14]. Thus, implanted nanostructured
biomaterials often decrease inflammation allowing for quicker new appropriate
tissue growth. Last, but not least, previous studies have demonstrated that
nanostructured biomaterials have excellent cytocompatibility properties towards
numerous cells (from osteoblasts to endothelial cells). In many cases, they have
lower
toxicity and integrate better with natural
tissue than conventional
biomaterials [15±19].
Because of the above, the field of nanostructured biomaterials (also called
nanomedicine) has already become a popular field for the synthesis and evalua-
