Biokinetics of nanoscaled europium oxide particles following an acute inhalation in rats

Nanoscaled europium oxide (Eu2O3) particles were selected to investigate the biokinetics following inhalation. The rare earth Eu allowed a very high accuracy in analysis of potential translocation from lungs to remote organs. An aqueous dispersion of commercially available Eu2O3 particles (0.1 w-%) was prepared in phosphate buffer (0.15 w-%) incl. bovine serum albumin (0.25 w-%). A suspension partially consisting of nanoscaled particles could be realized by mechanical homogenization and ultrasonic treatment and was aerosolized with pressurized air. Rats inhaled the dry aerosol for 6 hours in a single inhalation. Phosphate facilitated the disintegration of the Eu2O3 particles in lung ambience after deposition. The potential translocation of Eu2O3 particles was followed by chemical Eu analysis and transmission electron microscopy (TEM). Using chemical analysis, 36.8 <my>g/lung Eu2O3 were detected 1 hour after inhalation in lungs. The amount declined slightly to 34.5 ?g after 1 day and 35.0 ?g after 5 days. The liver showed an increase of Eu2O3 from 32.3 ng 1 hour up to 294 ng 5 days after inhalation. Additionally, lung-associated lymph nodes, thymus, kidneys, heart, and testes exhibited an increase of Eu2O3 over the time period investigated. In the blood, the highest amount of Eu2O3 was found after 1 hour whereas feces, urine and mesenteric lymph nodes revealed the highest amount after 1 day. In the other organs such as brain, spleen, adrenals and epididymides no changes of the Eu amount were detected. By TEM analysis, Eu2O3 particles could be detected only in lungs, in liver, however, with one of the highest chemical Eu concentrations, no particles were detectable. In conclusion, mixed type metal oxide/phosphate particles are a suitable tool for biokinetic investigations after inhalative uptake. The use of Eu2O3 combined with chemical and TEM analysis was a very suitable model to examine the translocation potential. Bioavailability was limited to soluble Eu2O3, a translocation of Eu2O3 particles was not evident.