Bioaccessibility of metals in alloys: Evaluation of three surrogate biofluids

- All alloy grades, independent of biofluid, revealed time-dependent release.
- Different alloy materials are useful for testing of bioaccessibility parameters.
- Minor changes in biofluid formulations have effects on bioaccessibility.
- Dissolution studies illustrated effects of alloy and media on metal dissolution.
- Metal solubility is compared in a series of alloys in various surrogate biofluids.

Bioaccessibility in vitro tests measure the solubility of materials in surrogate biofluids. However, the lack of uniform methods and the effects of variable test parameters on material solubility limit interpretation. One aim of this study was to measure and compare bioaccessibility of selected economically important alloys and metals in surrogate physiologically based biofluids representing oral, inhalation and dermal exposures. A second aim was to experimentally test different biofluid formulations and residence times in vitro. A third aim was evaluation of dissolution behavior of alloys with in vitro lung and dermal biofluid surrogates. This study evaluated the bioaccessibility of sixteen elements in six alloys and 3 elemental/metal powders. We found that the alloys/metals, the chemical properties of the surrogate fluid, and residence time all had major impacts on metal solubility. The large variability of bioaccessibility indicates the relevancy of assessing alloys as toxicologically distinct relative to individual metals.