Investigative Analysis of Lanthanum Oxide Nanoparticles on Elements in Bone of Wistar Rats After 30 Days of Repeated Oral Administration

Accumulation of lanthanum oxide nanoparticles (La₂O₃NPs) in the femur bone of rats after 30 days of oral administration was explored. Also, the influence of La₂O₃NPs on macro and trace elements in the rats' femur bone was assessed. Inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical spectrometry (ICP OES) were used for total element determination in the bone after decomposition while laser ablation-ICP-MS (LA-ICP-MS) was used to investigate element distribution (bio-imaging) in the bone. Some differences in element concentrations in the bone between the rats treated with La₂O₃NPs at 1.0 mg kg^-1 (T1), 10.0 mg kg^-1 (T2), and 100 mg kg^-1 (T3) body weight (bw) and the control rats (CTR) were observed. More differences were observed in the bone of rat treated with 10.0 mg kg^-1 La₂O₃NPs bw. However, the highest change observed was for Mg, which concentration ranged from 5230 ± 12 μg kg^-1 for the CTR group to 4130 ± 138 μg kg^-1 for the T3 group. Minor changes were observed for Ba, Ca, Cr, Cu, Fe, Mg, Na, Pb, Sr, and Zn between CTR and animals treated with La₂O₃NPs at the different levels of concentration. It was possible to observe from LA-ICP-MS analysis that La₂O₃NPs were accumulated only on the surface of the bone, not deeper than about 5 μm. LA-ICP-MS allowed also to investigate the distribution of La and the other elements in a cross section of the femur bone head, where higher amounts of the elements are present at the external part of the bone. Therefore, it was demonstrated that La₂O₃NPs are incorporated on the surface of the bone and it has a small influence on some of the other elements evaluated.