Biomedical Engineering Reference
In-Depth Information
Due to the brittleness of HA and lack of interaction with the polymer
matrix, ceramic nanoparticles may present deleterious effects on the
mechanical properties when loaded at high amounts. Coupling agents are
generally used to overcome the lack of interaction with polymer and nHA
aggregation (Li et al., 2008; Hong et al., 2005, 2004). In order to increase the
interfacial strength between PLLA and HA, and hence to increase the
mechanical properties, nHA particles were surface-grafted (g-HA) with the
polymer and further blended with PLLA (Li et al., 2008). The PLLA/g-HA
nanocomposites also demonstrated improved cell compatibility due to good
biocompatibility of the nHA particles and more uniform distribution of
the g-HA nanoparticles on the film surface (Li et al., 2008; Hong et al.,
2004). These nanocomposites are of great interest to the biomedical
community because the materials have a suitable structure that induces
and promotes new bone formation at the required site.
Calcium phosphate biomaterials certainly posses osteoconductive proper-
ties and may bind directly to bone under certain conditions (Nejati et al.,
2008). Calcium phosphate materials are suitable for calcified tissue
generation.
17.3.2 Metal nanoparticle-based nanocomposites
Silver (Ag) is known to have disinfecting properties and has found
application in traditional medicine. Ag nanoparticles have been investigated
for their antibacterial properties (Rai et al., 2009) and biopolymer-
embedded Ag nanoparticles have also been studied (Lee et al., 2006).
Nano-sized Ag permits a controlled antibacterial effect due to the high
surface contact area. For PLLA-based nanocomposite fibers including Ag
nanoparticles, antibacterial effects lasting longer than 20 days have been
reported (Xu et al., 2006). PLGA-based nanocomposites have also been
reported in the scientific literature (Schneider et al., 2008; Xu et al., 2008).
Metal nanoparticles enhance the thermal conductivity of the nanocompo-
sites and enhance the degradation rate (Xu et al., 2006). Furthermore, Ag
nanoparticles change the surface wettability and roughness of the
nanocomposites. For these reasons it is very difficult to control the bacterial
adhesion process.
It is also important to note that Ag nanoparticles have been listed under
carcinogenic materials by the World Health Organization (WHO). This
requires immediate and thorough action not only from environmental and
human health viewpoints, but also from the perspective of socio-economic
benefits (WHO, 2007).
