Gold nanoparticles have unique optical properties, which are exploited in nanomedicine for anti-cancer therapy and imaging. They are also incorporated into cosmetic or food formulations. However, the question of their long-term fate in cells remained unanswered, although it was commonly accepted that gold nanoparticles remained indefinitely intact in the lysosome, the cell’s “waste center”.
Contrary to these generally accepted ideas, scientists from the Matter and Complex Systems laboratory (CNRS / University of Paris), the Materials and Quantum Phenomena laboratory (CNRS / University of Paris), the Institute of Mineralogy, Materials Physics and cosmochemistry (CNRS / Sorbonne University / National Museum of Natural History / IRD) and the Strasbourg Institute for Physics and Chemistry of Materials (CNRS / University of Strasbourg) have shown, by following the evolution of nanoparticles or for 6 months in the cellular environment, that they underwent significant transformations within a few weeks. By measuring the expression of more than 18,000 genes over time, they have highlighted a biological process involving mechanisms of detoxification and cellular protection, also involved in the degradation of other nanomaterials. They thus noted both the presence of non-degraded nanoparticles and degradation products taking the form of nanosheets (see image).
Nano-sheets had already been observed almost 50 years ago in patients suffering from rheumatoid arthritis, who had been treated with another form of gold (ionic gold or “gold salts”) to relieve their joint pain. There would thus be a metabolism of degradation common between the gold salts and the gold nanoparticles.
This unexpected result, which generalizes the fate of gold nanoparticles in the body, could allow, in the future, to better assess the toxicity of these nanoparticles and their ability to be eliminated from the body. This interdisciplinary work also highlights that gold, whatever its initial form, can be metabolized by mammals even if it is not essential for their survival.