The behaviour of nanoparticles in the body after they are deposited in the lungs is reported online in Nature Biotechnology this week. The findings may have implications for future drug delivery, and in the study of air pollution and cancer development.

John Frangioni, Akira Tsuda, and colleagues used near-infrared fluorescent imaging to track nanoparticles administered to the lungs of rats. They varied the chemical composition, size and surface charge of the nanoparticles in order to determine which properties affect the transport of nanoparticles into tissues and their subsequent clearance from the body. The team shows that non-positively charged particles smaller than 34 nanometres in diameter are rapidly transported to lymph nodes, and that nanoparticles smaller than six nanometres with equal positive and negative charge are quickly cleared from the body via the kidneys.

With regard to the health effects of environmental pollutants, this work helps to explain why certain nanoparticles are more toxic than others. It also suggests that the toxicity of nanoparticle pollutants could be reduced by chemical strategies to alter their size and charge.