Nose-to-brain transport of aerosolised quantum dots following acute exposure

Nanoparticles are of wide interest due to their potential use for diverse commercial applications. Quantum dots (QDs) are semiconductor nanocrystals possessing unique optical and electrical properties. Although QDs are commonly made of cadmium, a metal known to have neurological effects, potential transport of QDs directly to the brain has not been assessed. This study evaluated whether QDs (CdSe/ZnS nanocrystals) could be transported from the olfactory tract to the brain via inhalation. Adult C57BL/6 mice were exposed to an aerosol of QDs for 1 h via nasal inhalation, and nanoparticles were detected 3 h post-exposure within the olfactory tract and olfactory bulb by a wide range of techniques, including visualisation via fluorescent and transmission electron microscopy. We conclude that, following short-term inhalation of solid QD nanoparticles, there is rapid olfactory uptake and axonal transport to the brain/olfactory bulb with observed activation of microglial cells, indicating a pro-inflammatory response. To our knowledge, this is the first study to clearly demonstrate that QDs can be rapidly transported from the nose to the brain by olfactory uptake via axonal transport following inhalation.