Biodistribution of inhaled metal oxide nanoparticles mimicking occupational exposure: a preliminary investigation using enhanced darkfield microscopy

• Published in: Journal of biophotonics 2016-10, Vol.9 (10), p.987-993
• Main Authors: Guttenberg, Marissa, Bezerra, Leonardo, Neu-Baker, Nicole M., del Pilar Sosa Idelchik, María, Elder, Alison, Oberdörster, Günter, Brenner, Sara A.
• Format: Article
• Language: English
• Subjects: Animals; Disease Models, Animal; engineered nanomaterials; enhanced darkfield microscopy; Exposure; histological samples; Inhalation; Inhalation Exposure; Kidneys; Lungs; Metal Nanoparticles - administration & dosage; Metal oxides; Microscopy; Nanoparticles; Occupational Exposure; Occupational health; Oxides; Rats; Tissue Distribution
• ISSN: 1864-063X; 1864-0648; 1864-0648
• DOI: 10.1002/jbio.201600125

Inhalation exposure to engineered nanomaterials (ENMs) may result in adverse pulmonary and/or systemic health effects. In this study, enhanced darkfield microscopy (EDFM) was used as a novel approach to visualizing industrial metal oxide nanoparticles (NPs) (silica, ceria, or alumina) in multiple tissue types following inhalation in rats mimicking occupational exposures. Advantages of EDFM over electron microscopy (EM) include reduced cost, time, and ease of sample preparation and operation. Following 4–6 hour inhalation exposures at three concentrations (3.5–34.0 mg/m3), lungs and secondary organs were harvested at 24 hours or 7 days post‐exposure and prepared for brightfield (BF) microscopy and EDFM. NPs were visualized within the lung and associated lymphatic tissues and in major organs of excretion (liver, spleen, kidney). EDFM also revealed NPs within pulmonary blood vessels and localization within specific regions of toxicological relevance in liver and kidney, indicating pathways of excretion. Results demonstrate the utility of EDFM for rapid direct visualization of NPs in various tissue types and suggest the potential for metal oxide NPs to distribute to secondary tissues following inhalation exposure. Confirmation of the composition, distribution, and relative abundance of inhaled NPs will be pursued by combining EDFM with hyperspectral imaging (HSI) and mapping. This study investigated the utility of enhanced darkfield microscopy (EDFM) for rapid visualization of metal oxide nanoparticles (NPs) following inhalation in rats mimicking potential occupational exposures. Silica, alumina, and ceria NPs in lung tissue, lung lymph nodes, and secondary organs (liver, kidney, spleen) were easily visualized with EDFM. Immediate next steps will combine EDFM with hyperspectral imaging (HSI) and mapping to confirm NP composition and assess NP biodistribution and abundance.