NANOTECHNOLOGY TO IMPROVE THE RECOVERY AFTER LONG NERVE DEFECT IN PERIPHERAL NERVE INJURIES

The repair of peripheral nervous lesion occurs only if fibres proximal to the injury can regenerate inside the distal stump reaching the target. In clinical practice this is made possible by means of a microsurgical suture of the two stumps. Anyway, in case of nervous substance loss, the microsurgical suture could prove not feasible and alternative strategies should be adopted. Nowadays, the gold standard in the treatment of large nervous gaps is still the autologous nervous graft. The reason for its success is ascribable to the presence of Schwann cells (SCs) inside the graft. These cells are able to provide neurotrophic factors and even an adhesion substrate along with the basal lamina with a function of support and promotion of axonal growth. This technique presents some inevitable disadvantages: the donor site injury, the need for a double surgical access and the disposal of a limited quantity of graft. For this reason, some alternatives to the nervous graft have been investigated such as nervous transfers (neurotisation) and tubulisation also known as Nerve Guidance Conduits (NGCs). In particular NGCs could employ biological or synthetic materials. Tubes are able to support axonal growth for short distances. Among biological tubes, some examples deserve to be mentioned: venous vessel, fresh or pre-degenerated muscle, alloplastic nerves muscle and vein associated. On the other side, the most used biomaterials for synthetic tubulisation are: silicon, polytetrafluoroethylene (PTFE), type I collagen, polyglycolic acid (PGA), polylactide caprolactone (PLCL), polyglycolic acid-collagen (PGA-c), chitosan, polyvinyl alcohol (PVA). Artificial tubes made of different types of biomaterial are now commercially available; they are generally empty tubes designed to protect and orientate nerve regeneration. NGCs are able to support a good quality of nervous regeneration only for gaps not longer than 30 mm, so they are not able to overcome the problem of large nervous tissue loss (> 50mm). In order to create more efficient neural guides, many studies have been conducted in the field of biochemistry, biophysics and bioengineering, investigating cellular answer to chemical and physical stimuli produced by extracellular environment.