Correlative microscopy and imaging secondary ion mass spectrometry for high resolution nano-analytics on biological tissue

Abstract text (incl. figure legends and references)

Introduction

Applications featuring sub-20 nm-imaging and chemical analysis at the same time typically rely on electron microscopy, which can be directly coupled to energy dispersive x-ray microanalysis (EDX) or used in combination with other tools like imaging mass spectrometry. Our group develops integrated focused ion beam (FIB)-based instruments featuring electron and/or ion primary beams, coupled to a double focusing magnetic sector secondary ion mass spectrometry (SIMS) system. This allows for correlative investigation of ultrastructure and chemical mapping within the same instrument at a lateral resolution of below 15 nm1.

Objectives

Presentation of a selection of application fields of FIB-SIMS in biology, nanotoxicology and beyond.

Material and Methods

Correlative electron (SE, BSE) and SIMS imaging of biological samples was performed using integrated FIB-SIMS instruments developed at LIST (e.g. Zeiss Orion Nanofab-SIMS, FEI Scios-SIMS). They yielded highly resolved chemical maps of elemental ions, their isotopes and respective small or large cluster molecules. Localisation and identification of pristine nanoparticles, but also metals embedded in complex matrices like tissue sections are performed. Additional detectors for e.g. transmitted helium beam detection on a Gas Field Ion Source (GFIS) equipped prototype instrument, called npSCOPE2, allow also correlative TEM-like imaging and analysis capabilities with helium beam at 20 - 30 keV and at temperatures down to -145°C thanks to the incorporation of cryo-setup capabilities.

Results

Uptake of foodborne nanoparticles by epithelial cells or bacteria, and nanoparticular redistribution of tattoo ink in skin phantoms and internal ion distributions of physiological elements are demonstrated.

Conclusion

High-resolution SIMS (< 15 nm resolution) enables detection of nanosized metal particles in biological tissue samples. In comparison to SEM-EDX at 10 keV, SIMS with 20-30 keV primary ion beams features both higher lateral resolution and sensitivity and provides isotopic information over a wide mass range. A cryo-workflow for the npSCOPE is currently under development (see abstract by Taubitz et al.) and will facilitate close to native chemical analysis of diagnostic, environmental and nanotoxicology samples.

Funding information: This project has received funding from the European Union"s Horizon 2020 Research and Innovation Programme under grant agreement No. 720964 and by the Luxembourg National Research Fund via the project INTER/DFG/19/13992454. Ink samples investigated as part of the COST COMULIS round robin study for novel correlative multimodal analyses (CA17121).

References:

1 Audinot et al. Highest resolution chemical imaging based on secondary ion mass spectrometry performed on the helium ion microscope. Rep Prog Phys 2021;84(10). doi: 10.1088/1361-6633/ac1e32.

2 De Castro, O. et al. npSCOPE: A New Multimodal Instrument for In Situ Correlative Analysis of Nanoparticles. Anal.