Where do nano particles go once they enter the body? ANSTO scientist helps shape new OECD guidance

New international best practice guidance, co-written at ANSTO, sets out how to measure where nanoparticles like titanium dioxide end up in the body and how long they remain.

The advisory has been shared by the Organisation for Economic Co-operation and Development (OECD), a forum and knowledge hub for data, analysis and best practices in public policy.

Scientists have well-established ways to measure how a dissolved chemical is absorbed, distributed and cleared by the body. The OECD test guideline for those studies was first adopted in 2010. It was written for chemicals that dissolve, and states that it is not intended for nanomaterials.

Poorly soluble nanoparticles are harder to follow. Once they reach the bloodstream, many are rapidly taken up by immune cells that clear foreign material, so very little ever shows up in a blood sample. The nanoparticles collect in a few organs, mainly the liver, spleen, lungs and lymph nodes, and can stay there for months or longer.
The OECD has now published guidance for how we can test the safety of nanoparticles that are taken up within our bodies. Its Guidance Document on Toxicokinetics to accommodate Testing of (Nano)particles sets out how researchers should design, conduct and report studies of nanoparticles that are swallowed or inhaled. ANSTO's Dr Paul Callaghan was part of the core expert group that wrote it, and the only member from the Southern Hemisphere.