Piezoelectric Nanomaterials

The next generation of biomaterials should include combinations of the above known stimulatory cues. Conductive or piezoelectric nanomaterials may elicit superior regenerative response compared to conductive, piezoelectric, or nanoscale materials alone. To date, few studies have combined nanomaterials with such known stimulatory electrical cues.

An electrical stimulus may be incorporated into a nanomaterial scaffold by selecting a material that is piezoelectric. Ceramics, such as zinc oxide (ZnO) and silicon dioxide, both have piezoelectric properties and have been fabricated into a variety of nanostructures. Though ZnO alone is not a suitable candidate for a NGC, it may be mixed with a polymer to form a nanorough composite which is flexible and can easily be fabricated into tubular shapes (Fig. 3). The piezoelectric response of nanomaterials may be superior to the piezoelectric response of a conventional material. The piezoelectric properties of the ZnO nanoparticles in these composites may be enhanced compared to their conventional material counterparts due to the large surface to volume ratio inherent to nanoparticles (Xiang et al. 2006). Atoms in nanoscale ZnO structures are able to assume different positions, due to the free

Fig. 3 Top left - Self assembled peptide amphiphile molecule nanofibers (Silva et al. 2004). Top right - electrospun PLGA/PCL fibers (Panseri et al. 2008). Bottom left - ZnO nanoparticles in PU (Seil and Webster 2008). Bottom right - neuron grown on carbon nanotube substrate (Hu et al. 2004)

boundary, which may enhance the piezoelectric effect. A significant piezoelectric response from these composites may provide the electrical stimulatory cues necessary to promote neural cell function.

A considerable number of ZnO nanostructures have been fabricated. Different structures will likely have different piezoelectric responses when mechanically deformed. Though ZnO nanoparticles with approximately spherical shapes are currently the only commercially available nanostructures (Nanophase Technologies, Romeoville, Illinois), other shapes can be synthesized with relative ease. Elongated structures may be more easily deformed to produce a piezoelectric effect.

Since a NGC is implanted to minimize tension on the nerve, it is unlikely that the scaffold will be mechanically deformed by the patient's own movement. Some form of applied stimulus will be needed to deform the scaffold. Ultrasound could potentially be applied near the area of the implanted scaffold to provide a transcu-taneous stimulus. Previous studies have shown that piezoelectric materials implanted beneath 3 cm of skin and soft tissue produced an electrical response when stimulated via external ultrasound (Cochran et al. 1998). Ideally, with respect to the information gathered from studies of axon guidance under an electrical stimulus, the direction of the electric field will be controllable. This could potentially be achieved either by aligning piezoelectric nanofibers in the scaffold or by applying a directional ultrasound stimulus to randomly oriented piezoelectric nano-particles or nanofibers.

Although ZnO and PCU composites are not biodegradable (and few, if any, piezoelectric materials are), they can serve as a useful model for investigating the efficacy of materials with both nanoscale and piezoelectric properties.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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