Polyethylene glycol (PEG) was reported to seal and repair damaged spinal cord  nerve cells,  by repairing the damaged membranes of nerve cells. Researchers lead by  Richard Borgens  and his team claimed that, PEG can restore the spinal cord's ability to transmit signals  to the brain. However, there is one possible clinical drawback: PEG's breakdown  products are potentially toxic. 
So, is there a biodegradable non-toxic  compound that is equally effective at targeting and repairing damaged  nerve membranes? Borgens teamed up with physiologist Riyi Shi and  chemist Youngnam Cho, who pointed out that some sugars are capable of  targeting damaged membranes. Borgens and his team  has  now come up with an interesting finding i.e.,  chitosan (see structure; source  : Wikipedia) can repair damaged nerve cell membranes. 
Having initially tested mannose and found that it did not repair spinal  cord nerve membranes, Cho decided to test a modified form of chitin, one  of the most common sugars that is found in crustacean shells.  Converting chitin into chitosan, Cho isolated a segment of guinea pig  spinal cord, compressed a section, applied the modified chitin and then  added a fluorescent dye that could only enter the cells through damaged  membranes.   Viewing a section of the spinal cord under the microscope, Cho was  amazed to see that the spinal cord was completely dark and none of the dye  had entered the nerve cells and Cho concluded that Chitosan had repaired the damaged cell  membranes.
Borgens is extremely excited by this discovery that chitosan is able to  locate and repair damaged spinal cord tissue and is even more  enthusiastic by the prospect that nanoparticles of chitosan could also  target delivery of neuroprotective drugs directly to the site of injury.
'giving us a dual bang for our buck,' says Borgens....
Ref : http://jeb.biologists.org/cgi/content/full/213/9/i-a
