Adv. Mater. doi:10.1002/adma.200703026 (2008)

Engineers at the University of Arizona in Tucson have developed a way to make metal nanoparticles that human kidneys should be able to eliminate. This would render the nanoparticles suitable for biomedical imaging with technologies such as optical coherence tomography.

Marek Romanowski and his co-workers used liposomes as templates to prepare hollow, gold spheres 63 nanometres in diameter that can scatter light of preselected wavelengths. The resultant balls of gold and lipid have different optical resonances from that of pure gold structures of the same size — and within the range of visible light.

The nanoshells break up to form 5.7-nanometre-dots when their lipid cores are degraded, which should happen inside the body. This would make the gold nanoparticles small enough to be cleared by renal filtration.