The apparent ability of some nanoparticles to get into the brain is certainly cause for some caution; to the degree that nanotechnology and molecular engineering will shape this century, we want to be certain that we don't trigger greater problems than we solve. But the ability to get into the brain turns out to have some potential benefits. University of Buffalo researchers have developed customized nanoparticles able to deliver genes into the brains of living mice "with an efficiency that is similar to, or better than, viral vectors and with no observable toxic effect."
The paper describes how the UB scientists used gene-nanoparticle complexes to activate adult brain stem/progenitor cells in vivo, demonstrating that it may be possible to "turn on" these otherwise idle cells as effective replacements for those destroyed by neurodegenerative diseases, such as Parkinson's.
In addition to delivering therapeutic genes to repair malfunctioning brain cells, the nanoparticles also provide promising models for studying the genetic mechanisms of brain disease.
The dangers of using viruses for gene therapy is that they may revert to "wild type," with potentially fatal results for the patients. Non-viral vectors don't have this problem.