Biomedical Engineering Reference
In-Depth Information
Pump
High-voltage
generator
Aerosol spray
Collector
FIGURE 4.2
Experimental set-up of the ESD technique.
applied over the nozzle, control the droplet size, which can vary between
hundreds of micrometers and several tens of nanometers, and the applied
voltage also controls the motion of the droplets.
40,41,46
Next to the ability to
control the properties of the coating, this technique also allows the incorpo-
ration of biological agents.
4.2 Nanofibers
A second category of nanomaterials, extensively studied by bone tissue
engineers, comprises nanometric fibers of natural and synthetic polymers.
Synthetic polymers can be divided into two groups, that is, degradable
and nondegradable polymers. For tissue engineering purposes, degradable
polymers are favored as they can be resorbed over a period of time, thereby
avoiding the long-term complications of a foreign substrate in the body.
47
Both natural and degradable synthetic polymers have already found appli-
cations in the field of tissue engineering, and the choice of polymer type
depends on the characteristics the construct should possess. Natural poly-
mers mostly resemble the ECM compounds; however, occasionally, they
are immunogenic or exhibit unsuitable mechanical properties.
48
Synthetic
degradable polymers, on the other hand, possess higher mechanical strength
and are mostly nonimmunogenic. Polymers can easily be shaped into porous
scaffolds by several techniques such as self-assembly, phase separation, sol-
vent casting and particulate leaching, freeze drying, melt molding, template
synthesis, gas foaming, and solid free forming. Most of these techniques,
