Nickel release and surface characteristics of fine powders of nickel metal and nickel oxide in media of relevance for inhalation and dermal contact

Abstract

Differences in surface oxide characteristics and extent of nickel release have been investigated in two thoroughly characterized micron-sized (mainly <4 μm) nickel metal powders and a nickel oxide bulk powder when immersed in two different synthetic fluids, artificial sweat (ASW-pH 6.5) and artificial lysosomal fluid (ALF-pH 4.5) for time periods up to 24h. The investigation shows significantly more nickel released from the nickel metal powders (<88%) compared to the NiO powder (<0.1%), attributed to differences in surface properties. Significantly more nickel was released from the nickel metal powder with a thin surface oxide predominantly composed of non-stoichiometric nickel oxide (probably Ni(2)O(3)), compared to the release from the nickel metal powder with a thicker surface oxide predominantly composed of NiO and to a lesser extent Ni(2)O(3) (88% and 25% release after 24 h in ALF, respectively). Significantly lower amounts of nickel were released from the nickel metal powders in ASW (2.2% and <1%, respectively). The importance of particle and surface characteristics for any reliable risk assessment is discussed, and generated data compared with literature findings on bioaccessibility (released fraction) of nickel from powders of nickel metal and nickel oxide, and massive forms of nickel metal and nickel-containing alloys.

Surface-protein interactions on different stainless steel grades: effects of protein adsorption, surface changes and metal release

“…However, a similar time-dependence has previously been observed in highly complexing solutions such as proteins and citric acid [8]. Minor initial increased rates followed by strongly decreased metal release rates for stainless steels and other passive alloys may be related to (i) complexation-induced metal release in the case of complexing solutions [33, 47], or (ii) slowly dissolving surface defects or inclusions, followed by a repassivation of the surface oxide [8]. Observed amounts of metals released into PBS were consistent with literature findings for stainless steel 316 in Hank’s solution (pH 7.4, no protein content) [48], while the corresponding release into protein containing PBS fluid was comparable with artificial lysosomal fluid (ALF, pH 4.5) [6].…”

Metal release from stainless steel in biological environments: A review

“…30 (4) Delayed release of metals (from grade AISI 304) in the presence of albumin, 23 which is typical for ligandinduced dissolution due to the relatively slow detachment step. 58,92,93 (5) Enhanced release of metals and enrichment of Cr in the surface oxide (grade AISI 316L) at increased albumin solution concentrations, despite the lack of significant change of the thickness and structure of the adsorbed albumin layer at albumin concentrations in solution above a threshold value. 38 This indicates that measured amounts of released metals in solution, at least to some extent, also involve surface-solution exchanged albumin.…”

Comparison of nickel speciation in workplace aerosol samples using sequential extraction analysis and X-ray absorption near-edge structure spectroscopy

“…25 Comparison studies of predominantly oxidic nickel particulate matter found that the Zatka method over-reported the amount of metallic nickel and under-reported the amount of oxidic nickel where the XANES analysis identied no Ni 0 . It is known that Ni powders have thin oxide surfaces that occur as the powders are passivated during formation.…”