Bioaccessibility of micron-sized powder particles of molybdenum metal, iron metal, molybdenum oxides and ferromolybdenum – Importance of surface oxides

Abstract

a b s t r a c tThe European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, that are manufactured, imported or used in different products (substances or articles) are identified and proven safe for humans and the environment. Metals and alloys need hence to be investigated on their extent of released metals (bioaccessibility) in biologically relevant environments. Read-across from available studies may be used for similar materials. This study investigates the release of molybdenum and iron from powder particles of molybdenum metal (Mo), a ferromolybdenum alloy (FeMo), an iron metal powder (Fe), MoO 2 , and MoO 3 in different synthetic body fluids of pH ranging from 1.5 to 7.4 and of different composition. Spectroscopic tools and cyclic voltammetry have been employed to characterize surface oxides, microscopy, light scattering and nitrogen absorption for particle characterization, and atomic absorption spectroscopy to quantify released amounts of metals. The release of molybdenum from the Mo powder generally increased with pH and was influenced by the fluid composition. The mixed iron and molybdenum surface oxide of the FeMo powder acted as a barrier both at acidic and weakly alkaline conditions. These findings underline the importance of the surface oxide characteristics for the bioaccessibility of metal alloys.

In Vitro Degradation Behavior and Biocompatibility of Bioresorbable Molybdenum

“…Dissolution rates of 0.6-18 µm/y and electrochemical corrosion rates of 5-13 µm/y were measured in various physiological solutions. These rates are in agreement with the corrosion rates for pure Mo of 0.32-9.47 µm/y reported by other groups [16][17][18][19][20] and close to the commonly referenced corrosion benchmark of 20 µm/y for a stent material [10]. The overall anodic dissolution reaction for molybdenum is:…”

Multi-walled carbon nanotube induces nitrative DNA damage in human lung epithelial cells via HMGB1-RAGE interaction and Toll-like receptor 9 activation

“…These metal compounds did not cause 8-nitroG formation, suggesting that metal impurities have no or weak ability to catalyze reactive species and cause DNA damage under the conditions used. It has been reported that iron and molybdenum were released from their particles in synthetic body fluid [ 51 ] and that nickel ions were released from nickel oxide nanoparticles in dispersion [ 52 ]. The bioavailability of metals used in this experiment appears to be comparable to those contained in MWCNT, although we cannot exclude the possibility that metal impurities remained insoluble in our experimental systems.…”

Mechanistic insight into reactivity and (geno)toxicity of well-characterized nanoparticles of cobalt metal and oxides

“…A 8 M NaOH (pH 13.6) was used as electrolyte in a volume of approximately 3 mL. Set-up details are given elsewhere (Morsdorf et al 2015). In brief, open circuit potential (OCP) measurements were performed in complete DMEM at pH 7.4 ± 0.1 for 48 h. Cyclic voltammetry (CV) measurements started from OCP (after 5 min stabilization), following a reduction at a rate of 0.0005 V/s to the lower water stability line (H 2 evolution peak) and an oxidation to the higher water stability line (O 2 evolution peak), or vice versa.…”