Surface reactivity measurements as required for grouping and read-across: An advanced FRAS protocol

Abstract

Abstract. Oxidative stress is a widely accepted paradigm associated with different adverse outcomes of particulate matter, including nanomaterials. It has frequently been identified in in vitro and in vivo studies and different assays have been developed for this purpose. Here we describe a newly developed multi-dose protocol of the FRAS assay (Ferric Reduction Ability of Serum). The purpose of this SOP is the measurement of the surface reactivity of nanomaterials under physiological conditions. Antioxidative components as present in human blood serum (HBS) serve as reporter molecules. The assay separates the oxidative damage from the read-out of the reporter molecules. The results show significantly enhanced repeatability with better sensitivity towards low reactivity, enabling application of FRAS both to a rough grouping by reactive vs. passive nanomaterials and further to substantiation of read-across by enhanced resolution of the similarity between different nanoforms of the same substance.

In Vitro and In Vivo Short-Term Pulmonary Toxicity of Differently Sized Colloidal Amorphous SiO2

“…For 9 nm, 15 nm, and 30 nm SiO 2 , very similar surface chemistry was recorded (determined by x-ray photoelectron spectroscopy [ 62 ]). Their specific surface reactivity (assessed by surface-induced biological oxidative damage and expressed as nM Trulox equivalent units per m 2 nanomaterial [ 62 ]) was also identical within error.…”

“…For 9 nm, 15 nm, and 30 nm SiO 2 , very similar surface chemistry was recorded (determined by x-ray photoelectron spectroscopy [ 62 ]). Their specific surface reactivity (assessed by surface-induced biological oxidative damage and expressed as nM Trulox equivalent units per m 2 nanomaterial [ 62 ]) was also identical within error. By contrast, the 55 nm SiO 2 had a significantly different surface chemistry and, accordingly, also showed significantly different specific surface reactivity (half the reactivity of the other materials, but still significant above background) ( Table 1 ).…”

“…Dissolution rate was determined as described by Wohlleben et al [ 98 ]. Surface chemistry and specific surface reactivity were determined by X-ray photoelectron spectroscopy and surface-induced biological oxidative damage, respectively, as described by Gandon et al [ 62 ]. Table 1 provides further details on the test material characterization.…”

Decision tree models to classify nanomaterials according to theDF4nanoGroupingscheme

“…The assay quantifies the decrease in the total antioxidant capacity in human blood serum which was incubated with nanomaterials as compared to unexposed human blood serum. An optimized FRAS assay protocol was described by Hsieh et al (2013) and further developed into an advanced multi-dose protocol by Gandon et al (2017). Briefly, human blood serum is incubated with nanomaterials, which are then removed by centrifugation.…”

Differences in the toxicity of cerium dioxide nanomaterials after inhalation can be explained by lung deposition, animal species and nanoforms

“…The surface reactivity was measured with the ferric reduction ability of serum (FRAS) assay(Gandon et al, 2017). The read-out of the FRAS assay is calibrated by a concentration series of Trolox(6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid, a Vitamin E analogon) and the result expressed as nmol Trolox Equivalent Unites (TEU)/m 2 NP.…”