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.