Calibration Strategy to Size and Localize Multi-Shaped Nanoparticles in Tissue Sections Using LA-spICP-MS

In the field of nanotoxicology, the detection and size characterization of nanoparticles (NPs) in biological tissues become increasingly important. To gain information on both particle size and particle distribution in histological sections, laser ablation and single particle inductively coupled plasma???mass spectrometry (LA???spICP???MS) was used in combination with a liquid calibration of dissolved metal standards via a pneumatic nebulizer. In the first step, the particle size distribution of Ag NPs embedded in matrix-matched gelatine standards introduced via LA was compared with that of Ag NPs in a suspension and nebulizer-based ICP???MS. The data show that the particles remained intact by the ablation process as confirmed by transmission electron microscopy. Moreover, the optimized method was applied to CeO2 NPs that are highly relevant for (eco-)toxicological research but, unlike Ag NPs, are multi-shaped and have a broad particle size distribution. Upon analyzing the particle size distribution of CeO2 NPs in cryosections of rat spleen, CeO2 NPs were found to remain unchanged in size over 3 h, 3 d, and 3 weeks post-intratracheal instillation, with the fraction of smaller particles reaching the spleen first. Overall, LA???spICP???MS combined with a calibration based on dissolved metal standards is a powerful tool to simultaneously localize and size NPs in histological sections in the absence of particle standards.

Automated summary

In the field of nanotoxicology, the combination of laser ablation and single particle inductively coupled plasma-mass spectrometry (LA-spICP-MS) with a liquid calibration of dissolved metal standards is used to detect and characterize the size of nanoparticles (NPs) in biological tissues. This method was able to preserve particle integrity during the ablation process and accurately analyze the particle size distribution of different types of NPs. The data obtained from studying Ag NPs and CeO2 NPs in biological sections demonstrate the potential of LA-spICP-MS for localizing and sizing NPs in the absence of particle standards.