Investigation of the interaction of uranium(VI) with the biofluids of the human digestive system

When radionuclides (RNs) enter the food chain and are ingested by humans, they pose a potential health risk due to their radio- and chemotoxicity. After oral ingestion, RNs first come into contact and interact with the biofluids of the digestive system. For the development of a rapid as well as ef-ficient method for the decorporation of RNs, it is necessary to know the biokinetic processes as well as the speciation in the digestive system. Therefore, the aim of this work was to investigate the in-teractions of uranium(VI) with the biofluids of the human digestive system, with the gastrointesti-nal digestive segments stomach and small intestine as well as the whole digestive system at the mo-lecular level. To simulate the biofluids, saliva, gastric juice, pancreatic juice and bile, and the diges-tive segments were synthesized based on human physiology.[1] For the determination of chemical speciation, luminescence spectra were measured using time-resolved laser-induced fluorescence spectroscopy under cryogenic conditions (cryo-TRLFS) at 153 K. Species distribution was then de-termined by parallel factor analysis (parafac), where the resulting species were assigned using the spectra of the individual complexes. These results were compared with thermodynamic modeling.
Based on the TRLFS experiments, it can be shown that the speciation of uranium is predominantly dominated by the inorganic components, mainly carbonate and to a smaller extent phosphate. Among the organic components, only the protein mucin is involved in speciation at acidic pH val-ues, such as in the stomach. Therefore, the complexation of mucin with uranium(VI) was investi-gated in more detail.

This work is funded by the German Federal Ministry of Education and Research (BMBF) under grant number 02NUK057A and is part of the joint project RADEKOR.

[1] Wilke, C. et al. (2017) J. Inorg. Biochem. 175, 248-258.