Microtechnology and nanotechnology in nerve repair.
OBJECTIVE
This review will describe the novel contributions to the field of nerve repair from the emerging disciplines of microtechnology and nanotechnology.


METHODS
This broad review will cover the advances described in the literature of the medical and biological fields and the engineering and physical sciences. The authors have also included their own work in this field.


CONCLUSIONS
Microtechnology and nanotechnology are providing two fundamentally different pathways for pursuing nerve repair: (1) microstructured scaffolds to promote regeneration and (2) direct repair by reconnecting axons. In the first instance, many of the traditional techniques for microfabrication of microelectronics have been applied to the development of implantable tissue scaffolds with precisely formed architectures. Combined with nanotechnological capabilities to control their surface chemistries, these tissue constructs have been designed to create a microenvironment within nerve tissue to optimally promote the outgrowth of neurites. With some initial successes in animal models, these next generation tissue scaffolds may provide a marked improvement over traditional nerve grafts in the ability to overcome nerve degenerative processes and to coax nerve regeneration leading to restoration of at least some nerve function. A second, completely different repair strategy aims to directly repair nerves at the microscale by acutely reconnecting severed or damaged axons immediately after injury and potentially forestalling the usual downstream degenerative processes. This strategy will take advantage of the traditional capabilities of microfabrication to create microelectromechanical systems that will serve as ultramicrosurgical tools that can operate at the micron scale and reliably manipulate individual axons without incurring damage. To bring about some restoration of a nerve's function, axon repair will have to be performed repetitively on a large scale and soon after injury. Development work is currently underway to bring about the feasibility of this technique.


CONCLUSIONS
With the emergence of microtechnology and nanotechnology, new methods for repairing nerves are being explored and developed. There have been two fundamental benefits from the technologies of the ultrasmall scale: (1) enhancement of regeneration using new tissue scaffold materials and architecture; (2) direct repair of nerves at the scale of single neurons and axons.
Chang
Wesley C
WC
Department of Ophthalmology, University of California, San Francisco, CA 94143, USA. changw@vision.ucsf.edu
Kliot
Michel
M
Sretavan
David W
DW
D000818:Animals; D006801:Humans; D055616:Microtechnology / Q000379:methods*; D036103:Nanotechnology / Q000379:methods*; D009416:Nerve Regeneration / Q000502:physiology*; D010523:Peripheral Nervous System Diseases / Q000628:therapy*; D023822:Tissue Engineering / Q000379:methods*