Phosphate/UO2 Interaction during In Vitro Dissolution of Inhalable Particles in a Medium Simulating the Phagolysosomal Compartment

Qualitative and quantitative methods have been developed to relate phosphate/UO2 interactions and U dissolution, in vitro, in a medium containing 0 or 10 mM phosphate concentrations at pH 5. This was performed by Energy Dispersive X ray Spectrometry (EDS) at 200 kV on entire particles and by fluorimetric measurement. The U dissolution rate was larger in a medium without phosphate than in a medium containing 10 mM phosphate. During the first day, the initial U dissolution involved 80.55% and 91.13% of the powder in media with and without phosphate respectively. From 5 to 15 d after beginning the assay, the dissolution half-times were longer than 92 d and 22 d for media with and without phosphate. EDS analyses have shown a constant P/U X ray intensity ratio for reference U2O(PO4)2 for the same range of particle diameter. A gradual increase of this ratio was measured for UO2 incubated in a 10 mM phosphate medium throughout the experiment.