Nanoparticles (with Nano Silver being the most commonly used) are potentially dangerous.

The possible long term effects have not been studied. However, it is an accepted fact that nanoparticles are so small that they can be absorbed through the skin and enter the blood stream, where their effects are unknown.
Why have the manufactures of these quality orthotics incorporated this untested, potentially dangerous "technology" into their products? Especially for such a superficial goal of odor control?!
"Every pair of Archmolds Custom Insoles comes with
Antibacterial Nano Silver imbedded into the topsheet of the insole. Nano Silver is comprised of anti-microbial silver particles which kill over 650 types of bacteria, including those that cause odor."
"Superfeet GREEN provides maximum support and shock absorption. Featuring
AgionŽ antimicrobial top cover treatment to reduce bacteria and help prevent foot odor."
More info at:
Our Silver-Coated Future - OnEarth Magazine, from NRDC, Fall 2007