Visualization and characterization of engineered nanoparticles in complex environmental and food matrices using atmospheric scanning electron microscopy

Abstract

Summary Imaging and characterization of engineered nanoparticles (ENPs) in water, soils, sediment and food matrices is very important for research into the risks of ENPs to consumers and the environment. However, these analyses pose a significant challenge as most existing techniques require some form of sample manipulation prior to imaging and characterization, which can result in changes in the ENPs in a sample and in the introduction of analytical artefacts. This study therefore explored the application of a newly designed instrument, the atmospheric scanning electron microscope (ASEM), which allows the direct characterization of ENPs in liquid matrices and which therefore overcomes some of the limitations associated with existing imaging methods. ASEM was used to characterize the size distribution of a range of ENPs in a selection of environmental and food matrices, including supernatant of natural sediment, test medium used in ecotoxicology studies, bovine serum albumin and tomato soup under atmospheric conditions. The obtained imaging results were compared to results obtained using conventional imaging by transmission electron microscope (TEM) and SEM as well as to size distribution data derived from nanoparticle tracking analysis (NTA). ASEM analysis was found to be a complementary technique to existing methods that is able to visualize ENPs in complex liquid matrices and to provide ENP size information without extensive sample preparation. ASEM images can detect ENPs in liquids down to 30 nm and to a level of 1 mg L−1 (9×108 particles mL−1, 50 nm Au ENPs). The results indicate ASEM is a highly complementary method to existing approaches for analyzing ENPs in complex media and that its use will allow those studying to study ENP behavior in situ, something that is currently extremely challenging to do.

Hydrodynamic chromatography coupled to single-particle ICP-MS for the simultaneous characterization of AgNPs and determination of dissolved Ag in plasma and blood of burn patients

“…To address this question, adequate analytical tools to detect AgNPs and dissolved Ag in the blood must be developed. Techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) enable size characterization of NPs at high resolution [8][9][10] but cannot provide statistically robust and quantitative data on complex biological fluids with a very low concentration of the metal. Dynamic light scattering (DLS) and static light scattering (SLS) are widely used to characterize NP suspensions but are also inadequate for the analysis of polydisperse particles in complex biological matrices [11,12].…”

Measurement and characterization of engineered titanium dioxide nanoparticles in the environment

“…Previous researchers already reviewed methods to characterize and measure ENPs in the environment (Tiede et al, 2008;Hassellöv et al, 2008;Stone et al, 2010;Silva et al, 2011;Tsao et al, 2011;Weir et al, 2012;Xiao and Wiesner, 2012;Zänker and Schierz, Gottschalk et al, 2013;Luo et al, 2013;Fabricius et al, 2014). Herein, a short overview is given on methods that may be used to study engineered TiO 2 -NPs.…”

Detection, characterization and quantification of inorganic engineered nanomaterials: A review of techniques and methodological approaches for the analysis of complex samples

“…A pioneer investigation of nanoparticles by ESEM in food samples was conducted by Gatti et al [80]. Luo et al [81] explored the application of ESEM to directly characterize the size distribution of a range of The use of electron microscopy for ENMs characterization in different types of samples has been considered in different reviews involving environmental [7,8,83], food [8,20], and biomaterials [71] analysis. In relation with complex samples, electron microscopy has been successfully applied to characterize TiO 2 nanoparticles in sewage sludge and soils amended with sewage sludge [84] or with biosolids [85], or to investigate the presence of ENPs in release studies: Ag NPs from a washing machine effluent [86] and from water-based nano-Ag spray products [87], TiO 2 NPs from textiles [88], or SiO 2 and Al 2 O 3 from chemical mechanical planarization process wastewater [89].…”

“…In relation with complex samples, electron microscopy has been successfully applied to characterize TiO 2 nanoparticles in sewage sludge and soils amended with sewage sludge [84] or with biosolids [85], or to investigate the presence of ENPs in release studies: Ag NPs from a washing machine effluent [86] and from water-based nano-Ag spray products [87], TiO 2 NPs from textiles [88], or SiO 2 and Al 2 O 3 from chemical mechanical planarization process wastewater [89]. SEM and TEM-based studies highlighted the relevance of the detection and characterisation of ENPs in many products of our daily life: Ag in washing solutions from commercial detergents [90], Ag and ZnO in spray products [91], TiO 2 and ZnO in sunscreens [74], metallic NPs in dietary supplement drinks [92], Ag in pears [93], SiO 2 in tomato soup [81] or coffee creamer [55], TiO 2 and ZnO in starch, yam starch, and wheat flour [94], or TiO 2 in foods and consumer product [95]. Regarding the implications of the presence of ENPs in biological samples, TEM can provide the most detailed information regarding in vitro nanoparticle uptake and localization by allowing both visualization of nanoparticle position within a cell or tissue and, in conjunction with spectroscopic methods, characterization of the composition of the internalised nanoparticles [96][97][98][99][100][101].…”