Stable isotope labeling of metal/metal oxide nanomaterials for environmental and biological tracing

Abstract

Engineered nanomaterials are often compositionally indistinguishable from their natural counterparts and thus their tracking in the environment or within biota requires the development of appropriate labelling tools. Stable isotope labelling has become a well-established such tool, developed to assign "ownership" or "source" to engineered nanomaterial enabling their tracing and quantification, especially in complex environments. A particular methodological challenge for the stable isotope labelling is to ensure the label is traceable in a range of environmental scenarios but without inducing modification of the properties of the nanoamaterial and without loss of signal from the label, thus retaining realism and relevance. This protocol describes the strategy for stable isotope labelling of several widely used metal and metal oxide nanomaterials, namely ZnO, CuO, Ag, and TiO 2 , using isotopically enriched precursors, namely 67 Zn or 68 Zn metal, 65 CuCl 2 , 107 Ag or 109 Ag metal, and 47 TiO 2 powder. A complete synthesis requires 1 to 8 days depending on the type of nanomaterial, the precursors used and the synthesis methods adopted. The physicochemical properties of the labeled particles are determined by optical, diffraction and spectroscopic techniques for quality control. The procedures for tracing the labels in aquatic (snail and mussel) and terrestrial (earthworm) organisms and monitoring the environmental transformation of labelled silver nanomaterials are also described. We anticipate this labelling strategy can be adopted by industry to facilitate applications such as nanosafety assessments before nanomaterials enter the market and environment as well as product authentication and tracking.

The Known and Unknown about the Environmental Safety of Nanomaterials in Commerce

“…Tracking the trace elements or metal contamination contained in the nanomaterials as a surrogate has shown some success for select materials such as carbon nanotubes and nano-scale zero-valent iron. [93,94] IStrategies such as isotopic labeling of nanomaterials such as carbon nanotubes, [95] and doping nanomaterials with low abundance rare earth metals, such as holmium (Ho) [88] Isotopic labeling still requires extraction of the nanotubes and specialized equipment for isotope detection. However, a more recent study has shown that using the doping method and spICP-MS nanoparticles can be detected at down to 1 × 10-3 ng L −1 in complex natural environments.…”

Nanomaterial Transformation in the Soil–Plant System: Implications for Food Safety and Application in Agriculture

“…For example, identification and quantification of transformation products in soil and plant tissues are challenging due to the presence of high background interferences in such samples. Advanced techniques such as synchrotron radiation based techniques (e.g., X-ray absorption fine structure spectroscopy) combined with imaging techniques including scanning transmission X-ray microscopy (STXM) and micro X-ray fluorescence (µ-XRF), [122] and isotope labeling approaches [49,123] coupled with in situ detection techniques such as autoradiography, [100] Nano Secondary Ion Mass Spectrometry (NanoSIMS), [124] laser ablation inductively coupled plasma mass spectrometry (ICP-MS), [125] and single particle/cell ICP-MS are all sophistical techniques that can be brought to bare for studying ENMs transformation. Metabolomics, [126] proteomics, [127] exposomics, [128] and secretomics [129] are emerging powerful tools to identify the components of root exudates, EPS, and plant/microbial metabolite response to ENMs exposure.…”

Influence of Aging on Bioaccumulation and Toxicity of Copper Oxide Nanoparticles and Dissolved Copper in the Sediment-Dwelling Oligochaete Tubifex tubifex: A Long-Term Study Using a Stable Copper Isotope

“…Thus, it allows the detection of 65 Cu body burdens in minute tissue samples, such as from T. tubifex (a few mg), despite the high Cu background levels in their tissue. One of the many advantages of this particular labeling method is that the label is incorporated into the NP during synthesis to have a unique isotopic composition throughout (Zhang et al, 2019). This makes the label more robust and reliable than labels attached to the surface, such as fluorescent markers, which can possibly be released (Schür et al, Reproductive output is presented as the mean ± SD number of cocoons at the end of exposure and hatchability (number of cocoons hatched, 2.5 months after exposure termination).…”

“…). An array of papers can be consulted for further discussion on the technique (Croteau et al, 2011b;Dybowska et al, 2011;Misra et al, 2012b;Zhang et al, 2019).…”