S. B. Seiffert, A. Vennemann, E. Niehaves, S. Kröger, M. Wiemann, U. Karst

Advanced Materials & Systems Research, Elemental Analysis, BASF SE, Carl‑Bosch‑Straße 38, 67056 Ludwigshafen am Rhein

Nowadays, nanomaterials are used in a wide range of applications such as consumer products, medical applications and in the field of catalysis. In the latter, automotive industries utilize CeO₂ nanoparticles due their special redox properties. Markable amounts of CeO₂ nanoparticles may thus be released into ambient air via the exhaust gases, posing a potential risk to human health. Several animal studies demonstrated that CeO₂ nanoparticles induce acute and chronic lung inflammation and, once in the blood circulatory system, are distributed in remote organs.

However, the distribution and size of CeO₂ nanoparticles in remote organs are not well understood as classical analytical methods provide limited information. They often only allow to obtain either the size of nanoparticles via tissue digestion or spatially resolved information. Here, we overcome this bottleneck by using laser ablation and single particle inductively coupled plasma-mass spectrometry (LA‑spICP‑MS) to investigate dissolution or aggregation by sizing and localizing of CeO₂ nanoparticles directly in tissue sections. Additionally, microsecond dwell times allow to distinguish between signals for dissolved material and nanoparticles, thus leading to improved particle resolution.

As no CeO₂ nanoparticles with narrow size distribution are commercially available, a quantification strategy using aqueous dissolved standards and matrix-matched gelatin standards to size and localize CeO₂ in liver and spleen from rats was developed. Analyses were performed after 3 hours, 3 days and 3 weeks following a single intratracheal instillation of 0.6 mg CeO₂ nanoparticles.

Our data indicate increasing particle size over the time. Additionally, hardly any dissolution was observed, thus confirming the chemical stability of CeO₂ nanoparticles in the organism after entering the body via the lung.