Antifreeze .... anyone?

A fairly low-key story appeared in a number of media reports yesterday on the use of nanoparticles in SCI. The reports (e.g. http://abcnews.go.com/Health/wireStory?id=9028713) surfaced following the epublication of a paper in the journal Nature Nanomedicine.

The nanoparticles in question are made from a compound found in antifreeze – polyethylene glycol (PEG). PEG has been quite extensively investigated as a drug delivery vehicle as it forms tiny hollow spheres into which drugs can be captured giving the drug combo distinct and often useful distribution characteristics. However, the group behind this most recent paper have been working on PEG as a therapeutic in its own right and have been doing so for some while now. Indeed, as far back as 1999 there were reports of positive effects following administration of PEG in guinea pigs and more recently in dog patients.

One of the properties of PEG is its ability to integrate with cell membranes and it is suggested this helps to patch up damaged axons that have become leaky after an injury. This in turn reduces the amount of toxic agents entering injured axons after injury and in so doing protects them from further secondary damage.

So what's new? The latest report combines PEG with another compound called poly-lactic acid (PLA) which produces particularly small diameter spheres. The combination appears to work better than PEG alone.

By all accounts the protective effects of these polymers requires very early administration (within hours post injury) which may prove difficult to achieve clinically.