Nanoparticles and the Brain

Contributed by: Michael Rafii, M.D., Ph.D - Director of the Memory Disorders Clinic at the University of California, San Diego. _______________________________

Nano particles are named for their small size (a nanometer is a billionth of a meter), and nano particles are smaller than anything humans have ever put into commercial products before, including sunscreen.

The smaller an object is, the larger its surface is in relation to its volume. Thus nano particles have an enormous surface to volume ratio, which renders them biologically active. This increased biologic activity can be either positive and desirable (e.g., antioxidant activity, carrier capacity for therapeutics, penetration of cellular barriers for drug delivery) or negative and undesirable (e.g., toxicity, induction of oxidative stress or of cellular dysfunction), or a mix of both.

Now public interest organizations are asking the FDA to 'Declare all currently available sunscreen drug products containing engineered nanoparticles of zinc oxide and titanium dioxide as an imminent hazard to public health.'

The nanoworld is quite a different place -- a world where particles can pass directly from the environment into your bloodstream, tissues, cells and organelles. There are three typical ways in which nanomaterials get into our bodies -- we breathe them, ingest them or absorb them through our skin. And despite the evidence that nanomaterials cause lung, liver and brain damage in animals, our Food and Drug Administration (FDA) is treating nanomaterials like their standard or bulk sized counterparts of yesteryear.

Once in the blood stream, nanomaterials can affect all of the organs and tissues of the body including the bone marrow, heart, lungs, brain, liver, spleen and kidneys. But little is known about what dose may cause harmful effects or how long different nanomaterials remain in various tissues.

Certainly more research is needed to answer the question of what effect nanoparticle may have on the human body, including the brain.