Conference Agenda

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a powerful tool for biological investigation as it can simultaneously detect various biomolecular species across length scales from cells to tissues, thanks to its high sensitivity coupled with high spatial resolution. ToF-SIMS has a role in spatial biology as a high-resolution multi-omic imaging platform that can detect elemental ions and metabolites, including intact lipids, label-free with subcellular spatial resolution without the need for matrix application¹. However, the direct label-free detection of intact peptides and proteins on tissue or within a cell is not currently feasible with a typical ToF-SIMS instrument. Multiplexed IHC techniques using tagged antibodies offer targeted protein imaging as it labels individual available proteins with reporters detectable with different MSI platforms. With our ToF-SIMS instrument and using metal-labelled antibodies, it is thus possible to detect multiple metal tags and thus multiple proteins in one imaging experiment. Here, we aim to use multiplexed ion beam imaging (MIBI™, IonPath, Inc.)² using metal conjugated antibodies to visualize protein expression on fresh frozen (FF) tissue along with complementary metabolite and lipid information on adjacent sections. We also describe the use of our state-of-the-art ToF-SIMS (PHI NanoTOF II) with tandem MS capability equipped with a liquid metal ion gun, C₆₀ ion gun, Ar cluster ion gun³.

Flash-frozen tissue blocks were sectioned with a thickness of 12 mm using a Leica cryostat microtome at -20°C. Serial sections from same tissue block were obtained and collected on clean indium tin-oxide coated glass slides. Prior to ToF-SIMS imaging, the tissue sections were dried using a vacuum desiccator for at least 3 hours. We were able to image elemental ions, metabolites and lipids in fresh-frozen tissue sections using a Bi liquid metal ion gun. We show complimentary images from adjacent serial sections using optical microscopy, standard histological staining (H&E staining), and ToF-SIMS imaging. In the next step, we will perform SIMS-based IHC where adjacent fresh frozen sections will be incubated with metal-conjugated antibodies.

Ultimately, we aim to develop a ToF-SIMS-based multi-omics pipeline to validate spatially resolved protein detection and have complementary metabolomic and lipidomic information on the same fresh frozen tissue sample. Correlative multi-omic imaging paired with same tissue architecture provides a way to investigate intermolecular mechanisms in biological tissues such as in disease progression and diagnosis in a single frozen tissue section.

References:

1 M. J. Taylor, J. K. Lukowski and C. R. Anderton, J Am Soc Mass Spectrom, 2021, 32, 872–894.

2 M. Angelo, S. C. Bendall, R. Finck, M. B. Hale, C. Hitzman, A. D. Borowsky, R. M. Levenson, J. B. Lowe, S. D. Liu, S. Zhao, Y. Natkunam and G. P. Nolan, Nat Med, 2014, 20, 436–442.

3 G. L. Fisher, A. L. Bruinen, N. Ogrinc Potočnik, J. S. Hammond, S. R. Bryan, P. E. Larson and R. M. A. Heeren, Anal Chem, 2016, 88, 6433–6440.

Human papillomavirus (HPV) infection causes approximately 5% of all new cancer cases. HPV types 16 and 18 causemore than 70% of high-grade cervical pre-cancers and 340,000 women die globally per year [1]. Moreover, HPV-positive (HPV⁺) oropharyngeal squamous cell carcinoma (OPSCC) has one of the most quickly ascending incidences in developed countries [2]. Only 28% of the HPV+ OPSCC cases are diagnosed early enough due to the lack of observed precursor lesions. Diagnostic methods that rely on histology, cytology, and HPV-DNA-based have certain limitations (e.g. non-quantitative) so there is a need to improve the imaging of oral lesions at a molecular level and meet the clinical need of identifying new disease-specific biomarkers. During the past two decades, imaging mass spectrometry (IMS) has arisen as a powerful tool for studying biological systems, because it provides label-free molecular characterization [3]. Here, we aim to develop a mass spectrometric image data analysis workflow for the identification of markers for PV-induced tumor tissues using a mouse papillomavirus (MmuPV1) model system [4]. This is followed up by tandem mass spectrometry measurements to unambiguously identify all marker species, allowing us to gain further insight into its role in HPV pathogenesis.

This proof-of-concept study uses IMS and a supervised machine classifier to identify novel biomarkers in PV-induced tumors. Flash-frozen skin tissue blocks of MmuPV1-infected [4] and control mice (N=5/group) were sectioned with a thickness of 12 mm using a Leica cryostat microtome at -20°C and thaw-mounted on conductive ITO-coated glass microscope slides. The analyzed areas were chosen based on matching with adjacent tissue sections, which were H&E stained. Prior to SIMS imaging, the tissue sections were freeze-dried for >2h. ToF-SIMS analyses were performed using a PHI nanoTOF instrument (Physical Electronics, USA) equipped with a Bi liquid metal ion gun. 30 keV Bi₃⁺ primary ions were used in all measurements. 500 μm × 500 μm images were rastered with 512 × 512 pixels. Forty frames were collected for each image with a cycle time allowing a 0–1850 Da mass range. Low-energetic 20 eV electrons of the flood gun compensated sample charging. Both positive and negative polarity ToF-SIMS images were acquired from 5 sample locations for each mouse, resulting in 100 image datasets. The data analysis workflow consisted of segmentation based on principal component analysis and K-means clustering in order to identify the hypodermis, the dermis, and the epidermis; allowing for a pair-wise comparison of infected and non-infected tissue layers. Prior knowledge of histopathologically identified tissue types of MmuPV1-infected and control mice then allows a random forest classifier to identify potential markers.

This work demonstrates the perspective of a supervised machine classifier on ToF-SIMS image data for the discovery of PV-induced tumor biomarkers, which subsequently could lead to new methods for early diagnosis of HPV⁺OPSCC.

1. D. K. Gaffney et al. Gynecol. Oncol. 2018, 151, 547.
2. M. Lechner et al. Nat. Rev. Clin. Oncol. 2022, 19, 306.
3. S. Van Nuffel et al. Anal. Chem. 2020, 92, 12079.
4. J. Hu et al. Viruses 2017, 9, 246.

Retrieval of fingermark evidence from bullet casings is an area of major difficulty for forensic scientists. This is due to both the physical conditions, e.g. high temperature, pressures and large friction forces, that are experienced by the bullet casings during firing and the techniques used to develop and image the fingermarks. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a highly sensitive surface analysis technique that can map different chemicals on a surface and has shown great promise for the retrieval of fingermarks from flat metallic surfaces. We have developed a high precision ultra-high vacuum (UHV) rotation stage that allows the surface of cylindric bullet casings to be imaged using ToF-SIMS. Experiments were performed over a period of seven months to investigate how fingermarks deposited on the surface of cylindrical bullet casing (Webley MkII round) change over time. The ToF-SIMS analysis was performed by analysing a thin strip along the length of a casing before rotating it by a few degrees and analysing a new strip. The process was repeated until the entire casing has been imaged. Obtained images were then stitched together. ToF-SIMS images of the fingermarks were found to show clear ridge and sweat pore detail on samples that showed no evidence of fingermarks when developed using cyanoacrylate fuming and subsequent staining with Basic Yellow 40 (BY40) dye. ToF-SIMS images were also compared to fingermarks that had been deposited onto flat paper surfaces using ink to assess the effects of the curvature of the cylindric casings on the morphology of fingermarks. The distortions caused by differences in surface curvature were found to be within acceptable limits.

Batteries play a pivotal role in the ongoing energy transition from fossil fuels to sustainable sources by efficiently storing energy. Among various battery types, Li-ion batteries have gained significant prominence in electric vehicles and consumer electronics, primarily attributed to their high energy density.

Therefore, the demand for Cathode Active Materials (CAMs) with a high specific capacity is steadily growing, where nickel rich layered oxides are already promising candidates. Specific capacity of nickel-rich layered oxides surpasses other classes of cathode active materials (CAMs), such as lithium-manganese rich spinels and lithium iron phosphate olivine phase, demonstrating their superior performance. However, the higher nickel content in these layered oxide materials also makes them more sensitive to moisture, particularly water.

Following the synthesis process, residual lithium salts on the CAMs surface, which have a negative effect on their electrochemical performance. Consequently, the synthesis residuals are removed during post-processing through a water washing step. Unfortunately, the interaction between the CAM and water during this washing step leads to an exchange of H⁺ and Li⁺-ions, thereby reducing the available lithium inventory and thermostability of the CAM.

In addition to the washing step, the water-based thin film casting of electrode sheets is gaining increased attention for its potential to eliminate the use of NMP (N-Methyl-2-pyrrolidone) in battery manufacturing processes, thereby enhancing their environmental friendliness. Moreover, during the water-based thin film coating process, there is an exchange of H⁺ and Li⁺-ions in the cathode active material.

This study focuses on the characterization of H⁺-Li⁺-exchange between water and nickel rich CAM using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). To achieve a better depth resolution with the ToF-SIMS, a flat nickel- rich layered oxide model system is prepared and washed with deuterated water. The ToF-SIMS technique is then employed to investigate the change in the surface structure and the depth of H⁺ and Li⁺ exchange. The main objective of this research is to determine the kinetics of the H⁺-Li⁺ exchange process for nickel-rich CAMs. Enhancing our understanding of the H⁺-Li⁺-exchange process can be leveraged to optimize processing parameters for synthesizing nickel-rich cathode active materials and water-based film coating of cathode electrodes.

Skin ageing, characterized by wrinkles, hyperpigmentation, and the loss of elasticity is a multifaceted process that can be intrinsic or extrinsic in nature³. Vitamin C (ascorbic acid) is a powerful antioxidant, commonly used in skincare creams to tackle skin ageing by reducing reactive oxygen species (ROS), preventing the suppression of collagen production and promoting the transcription of procollagen I and III genes in cells⁴. The topical use of this compound is currently restricted, due to its instability and susceptibility to be oxidised⁵. Information regarding the depth and lateral distribution of active agents such as vitamin C would be highly informative and could help optimise skincare systems. However, this information is very difficult to ascertain, especially in-vivo.

Mass spectrometry Imaging techniques, such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) and 3D OrbiSIMS are rapidly gaining popularity in the characterisation of the molecular structure of the skin and its integrity, especially the barrier layer known as the stratum corneum^1,2. These techniques offer relatively high mass and spatial resolving power, with the possibility of exploring the permeation of cosmetic actives as a function of depth.

In this research, the permeation and lateral distribution of vitamin C, from a commercially available product, through the stratum corneum was established using ToF-SIMS and OrbiSIMS. A study was performed to understand the impact of exposure time using both ex-vivo porcine skin and in-vivo human tape strips. It was observed that permeation was the deepest at 24 hours, whilst still being localised at the surface of the stratum cornuem after 4 and 8 hour exposure times. The lateral distribution of vitamin C was demonstrated as being heterogenous, localised in pools of high intensity through all the layers of the stratum corneum. Both the ToF-SIMS and OrbiSIMS analysis were capable of detecting the vitamin C within the skin, however, the OrbiSIMS demonstrated a significantly enhanced sensitivity.

1. P. Sjövall, S. Gregoire, W. Wargniez, L. Skedung and G. S. Luengo, Int J Mol Sci, 2022, 23, 13799.

2. N. J. Starr, M. H. Khan, M. K. Edney, G. F. Trindade, S. Kern, A. Pirkl, M. Kleine-Boymann, C. Elms, M. M. O’mahony, M. Bell, M. R. Alexander and D. J. Scurr, , DOI:10.1073/pnas.

3. K. Biniek, J. Kaczvinsky, P. Matts and R. H. Dauskardt, J Dermatol Sci, 2015, 80, 94–101.

4. Y. C. Boo, Antioxidants, 2022, 11, 1663.

5. N. J. Starr, D. J. Johnson, J. Wibawa, I. Marlow, M. Bell, D. A. Barrett and D. J. Scurr, Anal Chem, 2016, 88, 4400–4408.

Characterisation of peptides and proteins within a biological specimen is of great importance for clinical proteomics to improve disease classification and to identify new therapeutic agents. Previously, studies of these biomolecules with Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) has been limited due to the chemical damage caused by the monoatomic or small cluster beams to the analyte [1]. However, with application of the large gas cluster beams, the detection of these biomolecules is now feasible since they impact the surface as a single entity [2,3,4]. This results in a very gentle ion emission with a consequence of very low fragmentation of the emitted molecular ion.

Here we show with water gas cluster ion beam (H₂O)_n, small proteins can now be detected as intact multiply charged species; whereas with (Ar/CO₂)_n beam these ions are not produced or the formation of fragments is favoured. We also explore the effect of sample preparation and analysis conditions on the formation of multiply charged ions of a peptide/protein. An improved sensitivity for 2+, 3+ and 4+ ions of peptides/proteins will provide a new route of detection of large proteins by SIMS.

References

[1] B.J. Garrison, Z. Postawa, ToF-SIMS: Materials Analysis by Mass Spectrometry 2^nd Ed, 2013.

[2] S. Sheraz, I. B. Razo, T. P. Kohn, N. P. Lockyer, J. C. Vickerman, Anal. Chem. 87, 2367 (2015).

[3] A. M. Kotowska, G. F. Trindade, P. M. Mendes, P. M. Williams, J. W. Aylott, A. G. Shard, M. R. Alexander, D. J. Scurr, Nat. Commun. 11, 5832 (2020).

[4] H. Tian, S. Sheraz née Rabbani, J. C. Vickerman, N. Winograd, Anal. Chem. 93, 7808 (2021).

Perovskite oxides are widely used in different solid oxide fuel cell (SOFC) components. SOFCs are highly efficient devices that can generate energy by electrochemically combining hydrogen and other fuels with oxygen. They are composed by an assembly of thin ceramic layers (cathode/electrolyte/anode). The operation of SOFCs involves the oxygen reduction at the porous cathode, transport of oxygen ions throughout the dense electrolyte, and the oxidation of the fuel at the porous anode. Among the perovskite oxides used in SOFC, La_1-xSr_xGa_1-xMg_xO_3-d (LSGM) is one of the most promising electrolyte materials due to its high ionic conductivity. Nevertheless, pure LSGM phase is really hard to obtain and there is a wide discrepancy in the literature regarding the secondary phases formed under different sintering conditions. Bulk characterization techniques such as Energy Dispersive Spectroscopy-Scanning Electron Microscopy (EDS-SEM) and X-ray diffraction (XRD) are generally used for identifying these secondary phases, which might yield misleading conclusions since the volume occupied by these secondary phases is usually smaller than the volume analyzed by using these bulk techniques. In this regard, surface analysis techniques such as TOF-SIMS can provide valuable complementary information for identifying the secondary phases present in LSGM samples.

This work aims at studying the elemental distribution on the surface of LSGM pellets sintered at different temperatures. Commercial (La_0.9Sr_0.1)_0.98Ga_0.8Mg_0.2O_3-d (Praxair) and La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-d (Fuel Cell Materials) powders were uniaxially pressed and thermally treated in air at different temperatures within the 1200-1400 ºC range. The surface chemical composition of the pellets was investigated by TOF-SIMS imaging and depth profiling. In addition, the crystallographic phases present in each sample were identified by XRD while the bulk chemical composition was analyzed by EDS/SEM. Even though the effect of electrical charging and the topography of the samples can hinder the interpretation of TOF-SIMS data, the performed analysis demonstrate that TOF-SIMS is a useful complementary technique for a better interpretation of XRD and EDS/SEM results and for the understanding of LSGM phase formation mechanisms.

Pulsed laser deposition (PLD) is one of the most common techniques to grow oxide thin films with a complex composition. However, the congruent transfer of the target composition to the film can be a difficult task. This is particularly noticeable when depositing materials composed of elements with a large mass difference, which can lead to a significant deficiency of light elements in these films, such as Li. Given that many Li-containing materials are very sensitive to the exposure to air due to the formation of lithium carbonate or lithium hydroxide, it is essential to use in situ tools to gain a direct insight into growth properties of as-deposited films.
An ultra-high vacuum PLD-chamber equipped with various analytical techniques, including optical emission spectroscopy, plasma imaging, plasma mass spectrometry and secondary ion mass spectrometry (SIMS), has been designed to perform comprehensive studies on the chemical composition of the ablation plume, energetics of the plasma, time-resolved expansion profile of chemical species in the plume and the chemical composition of in situ grown films. We investigated the laser induced plume dynamics of Li_xMn_yO_z and analyzed in situ and ex situ grown films using SIMS depth profiling. The difference in the elemental distribution as a function of thickness of the Li_xMn_yO_z films revealed changes at the surface upon air exposure. In situ SIMS was also used to characterize films grown under different background pressures (10^-8 to 10^-1 mbar of O₂), and results are correlated to differences observed by plasma imaging like differences of the Li and LiO distributions in the plasma plume. In addition, in situ SIMS was carried out at different stages of the PLD process, which revealed differences in the distribution of the elements throughout the film upon annealing.

ToF-SIMS is an excellent method to observe changes in lipids, which are known to play an important role in neurodegenerative diseases. The introduction of an argon cluster ion beam into ToF-SIMS has made it more favorable for observing higher-mass lipids. However, the ability of ToF-SIMS to identify lipids was still limited. To identify lipids, MS/MS capabilities have recently been introduced to ToF-SIMS. To obtain MS/MS spectra, the orbitrap mass spectrometer with a long-pulse argon cluster ion beam is used. In this study, mass spectra and images were obtained from the mouse brain tissue using pulsed argon cluster ion beam in ToF-SIMS. ToF-SIMS mass spectra obtained with a pulsed argon cluster ion beam were compared to orbitrap mass spectra obtained with a long-pulsed argon cluster ion beam. From this results, we can see that there is no significant difference between the mass spectra obtained with ToF-SIMS and OrbiSIMS. The OrbiSIMS spectra showed better mass resolution and mass accuracy. MS/MS spectra obtained using the orbitrap were compared to LC-MS/MS spectra used as a golden standard, and the MS/MS spectra obtained from the two instruments were similar.

ToF-SIMS is a surface chemistry analysis that provides information at the molecular level on the surface of a sample. In the field of polymers, it has been utilized for composition analysis and copolymer component discrimination using backbone-specific repeat units [1]. However, due to the complexity of ToF-SIMS data, distinguishing chemically similar types of polymers remains a challenge. In particular, for various materials that share a backbone in the hydrocarbon family, such as plastics, it is still difficult to distinguish them by their surface mass spectra. It has been reported that SOM methods can be applied to ToF-SIMS data for polymer classification and protein orientation analysis [2,3].

We applied machine learning techniques to spectral data of plastic samples and their raw materials to explore various ways to distinguish of similar structures. In particular, we analyzed the features that contributed to the distinction of each plastic, i.e., the main unit components, through feature extraction. We propose a machine learning method to extract features with optimal classification performance in microplastic classification. Through this, we were able to successfully distinguish five types of plastics and present the features of each plastic.

The development of new polymeric materials with ever more micro- to nano-sized structures is gaining significant interest in different fields, such as optical devices, biology, molecular electronics with a large focus in the battery field. The versatility of the polymers can be specially seen in the battery field where polyelectrolytes have been applied as both solid electrolyte materials (polymer electrolytes. Poly(ionic) liquids, single ion conductors, etc.) and as binders for high-capacity anodes [1]. Moreover, to further optimize the electrochemical performances of new-generation batteries, an ever-increasing effort to employ micro/nanophase separated polymer materials or nano particles containing composites has been observed in recent years. However, the use of such new polymer materials led to an enormous challenge in terms of their characterization, microscopy, chemical micro- and nano-analysis. Therefore, the development of new advanced characterization techniques providing excellent spatial resolution and high-sensitivity elemental information is of upmost importance.

A multimodal imaging instrument combining the Helium Ion Microscope (HIM) and Secondary Ion Mass Spectrometry (SIMS) has been developed at LIST allowing for in-situ correlative microscopy. The system combines the ZEISS ORION NanoFab HIM using a Gas Field Ion Source (GFIS), and a magnetic sector SIMS system [3]. During secondary electron (SE) imaging, He⁺ and Ne⁺ scanning can achieve resolutions down to 0,5 nm and 2 nm, respectively, while in SIMS imaging the instrument has the capacity to reach lateral resolutions down to 15 nm [4]. On top of 2D and 3D images, mass spectra and depth profiles can also be acquired on this instrument.

Here, we will present the preliminary results obtained on polymer samples, highlighting the advantage of using light ions (i.e., He⁺ and Ne⁺) in SIMS to provide high spatial resolution information and to reduce the fragmentation of the polymer material in DC mode. A related methodology was developed on thin films samples representing blends of immiscible polymers, namely of polystyrene and poly(methyl methacrylate)[5]. A special focus was put on the SIMS fragment identification, phase domain distribution and phase separation mechanism.

This work was co-funded by the Luxembourg National Research Fund (FNR) through the grant INTER/ DFG/22/16558792/MINABATT

References

[1] A. M. Wilson., G. Zank, G. Eguchi, W. Xing, & J. R. DahnIn J. Power Sources 68:195–200 (1997).

[2] D. Deng, (2015). Energy Science and Engineering Vol. 3, Issue 5, pp. 385–418 (2015).

[3] J. N. Audinot, P. Philipp, O. De Castro, A. Biesemeier, Q. H. Hoang, T Wirtz, Reports Prog. Phys. 84, p.105901 (2021).

[4] D. Dowsett, T. Wirtz, Analytical Chemistry, 89(17), 8957–8965 (2015).

[5] L. Kailas, J. N. Audinot, H. N. Migeon, & P. Bertrand, Composite Interfaces, 13(4–6), 423–439 (2006).

Sporadic Parkinson’s disease (PD) is a neurodegenerative disease affecting mostly the elderly. One characteristic change observed in the brain during aging and PD is the neuronal accumulation of iron and other reactive metals in substantia nigra (SN) and locus coeruleus (LC), mainly occurring in cytoplasmic stores and so-called neuromelanin (NM) organelles. Several spectroscopic studies (e.g. Zecca et al PNAS 2004; Biesemeier et al J Neurochem 2016) investigated the role of quantitative and molecular changes of metals in the SN during aging and disease progression. However, no studies were performed using high lateral resolution techniques for subcellular (re)distribution analyses or were concerned with the elemental composition of LC and its involvement in PD.

This work studies the subcellular and even sub organellar distribution of toxic metals in the NM-containing organelles (having melanin, lipid and protein-based partitions of < 100 nm in diameter) of LC in aging and PD using established and novel analytical approaches based on secondary ion mass spectrometry (SIMS).

Analyses are performed on available resin-embedded human LC tissue prepared for analytical transmission electron microscopy (aTEM). 100 nm thin epoxy sections were first quantitatively analysed using aTEM and then by CAMECA NanoSIMS 50 (caesium and oxygen beams), with the ability for isotopic identification, highest sensitivity and mass resolution, and a lateral resolution down to 50-100 nm for chemical imaging. Sub organellar distribution of metals in NM-containing organelles is addressed on selected samples using FIB-SIMS (gallium, helium and neon primary ion beams, lateral resolution < 20 nm for SIMS; < 1 nm for secondary electron (SE) imaging) developed at LIST. TEM like ultrastructural investigation is possible on the so-called npSCOPE, a novel cryoFIB-STIM-SIMS platform based on ultra-high brightness Gas Field Ion Source (GFIS; Primary ion species He and Ne, Anal Chem. 2021, 93 (43), p14417) with SE, SIMS and scanning transmission ion microscopy (STIM) detectors (Beilstein J. Nanotechnology 11 (2020), p1854). The same instrument will be used in future to perform respective analyses on frozen-hydrated brain samples to minimize preparation artefacts.

Here we present first results for the chemical identification of melanin-based and cytoplasmic metal storage sites for sodium, aluminium, calcium and iron in nor-adrenaline neurons of LC. A semi-quantitative FIB-SIMS approach is formulated where a sample is imaged first at high resolution using SE or STIM imaging to identify the region of interest and then SIMS maps are acquired with a field of view of about 5 – 70 µm for the chemical identification and metal storage of particular areas in the tissue with higher sensitivity then aTEM. Future investigations on cryopreserved specimen with the cryoFIB-STIM-SIMS platform or cryoTOF-SIMS for molecular analyses will give a more detailed view on the role of metal loading of NM in brain aging and Parkinson’s disease that could help in analysing biological samples very close to their native state.

This work has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement no. 720964 and was supported by the Luxembourg National Research Fund via FNR CORE C21/BM/15754743 and INTER/DFG/19/13992454.

Chronic sleep deprivation (CSD) is a detrimental condition leading to enhanced oxidative stress, which is closely associated with the development of various diseases including cardiovascular disorders, cognitive dysfunction, metabolic syndrome, and impaired reproductive activity. Considering zinc (Zn) is the second-most necessary trace element playing an important role in the regulation of anti-oxidative defense network and initial stages of spermatogenesis and fertilization, the primary objective of this study is to determine whether the testicular expression of Zn would significantly be altered following CSD. Adult Wistar rats subjected to three cycles of CSD with each cycle consisting of five consecutive days of total sleep deprivation followed by a two-day break were used in this study. The testicular level and intensity of Zn were determined by the time-of-flight secondary ion mass spectrometry (TOF-SIMS). The functional significance of Zn was evaluated by the extent of oxidative level, the expression of Cu/Zn superoxide dismutase (Cu/Zn SOD), and the sperm mobility. Results indicated that in normal untreated rats, fine sperm motility with extensive high levels of Zn, abundant expression of Cu/Zn SOD, and low oxidative stress was detected in the testicular tissues. However, following CSD, a significant reduction of Zn expression, decreased activation of Cu/Zn SOD, and excessive increase of oxidative stress were all observed in testicular samples. Reduced expression of Zn coincided well with the substantial decline of sperm motility. Based on these findings, the present has provided for the first time that impairment of testicular Zn expression, together with reduced activation of Zn-related anti-oxidative enzymes may serve as the underlying mechanism(s) for the pathogenesis of CSD-induced reproductive disability.

In its current state, the fashion industry is unsustainable. Sustainability issues include incineration and landfill disposal of clothes and microplastic shedding during washing.

Fabric care products aim to alleviate these issues by extending the lifetime of clothes. Biologically based formulations investigated herein have been evaluated previously with bulk applications tests to demonstrate product performance benefits.

However, little is known about their mechanisms of action. To investigate these, and ultimately develop new improved fabric care products, biomolecule-fabric interactions have been studied with Atomic Force Microscopy (AFM), Secondary Ion Mass Spectrometry (SIMS), and Dynamic Mechanical Analysis (DMA).

A greater degree of biomolecule permeation in natural versus artificial fabrics, surface coating homogeneity, presence following consumer washing, and biomolecule mode of action of reduction of inter-fibre fiction is presented.

The application of SIMS to biological materials has expanded substantially in the last decade ⁽¹⁾. There have been important advances in technology including the use of a wide range of gas cluster ion beams for analysis using argon ⁽²⁾, water / CO₂ mixtures ⁽³⁾ and water ⁽⁴⁾. In addition, new analysers have been developed for improved biological analysis including the J105 ⁽⁵⁾ (Ionoptika, UK) and the OrbiSIMS ^(6,7) (Hybrid-SIMS, IONTOF GmbH, Germany) amongst others. SIMS now allows molecular imaging of complex biological samples ranging from cells to tissues. To improve repeatability and determine reproducibility between laboratories with varying instrument configurations there is a need to define and establish a biologically relevant biomimetic sample for pharmaceutical and small molecule analysis.

In this study, we present a step-by-step approach for sample preparation of a biomimetic reference material composed of doped tissue homogenate from rat liver using a protocol developed by GlaxoSmithKline for MALDI MS ⁽⁸⁾. The resulting material was characterised using ToF-SIMS (Bi₃⁺ analysis beam) and OrbiSIMS (Ar₂₅₀₀⁺) depth profiling. The spiking of different drugs in the resulting material is used to study the influence of matrix effects on detection sensitivity ⁽⁹⁾, limit of detection and calibration for quantification. This study evaluates the possibility of using this reference material for a future VAMAS interlaboratory comparison suitable for dual beam and single beam analysis instruments.

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Aluminium-lithium alloys are extensively used in aerospace applications due to the improved properties the addition of Li has on the Al alloy system. Low density alloys are extremely important in aerospace applications due to the increasing demand to reduce fuel consumption thereby reducing greenhouse gas emissions and save cost. For every 1 at% of Li added to the aluminium alloy, the density is reduced by 3%. The distribution of Li and its precipitates have a major effect on the properties of the alloy. Although Al-Li alloys have been in development since the 1920’s, there are still challenges associated with their production, for example when Al-Li alloys are cast the Li does not remain evenly distributed throughout the casting due to its low density. Current research is investigating if additive manufacturing can generate a uniform distribution of Li in these alloys. However, it is analytically very challenging to spatially localise the Li distribution with traditional techniques such as with energy dispersive X-ray spectroscopy in a scanning electron microscope. As it is difficult to determine the Li distribution it is hard to understand the role it plays in alloy strengthening in conventionally produced and additively manufactured alloys.

In this project high spatial resolution secondary ion mass spectrometry (NanoSIMS 50L) and Electron Probe Microanalysis (EPMA) with a wavelength-dispersive soft X-ray emission spectrometer (WD-SXES) are used to characterise Wire + Arc additive manufacturing (WAAM) produced Al-Li alloys. The results show that in the as-produced alloy the precipitates are highly complex containing a wide range of elements that have co-precipitated. This presentation will show how the NanoSIMS is able to map Li at high lateral resolution which is necessary as the Li-containing precipitates are less than a micron in size. However, the exact type and composition of the complex precipitates are yet to be determined and further complementary EPMA work is required to achieve this. The next stage of this project is to combine the NanoSIMS and EPMA WD-SXES data to quantify the Li in both the precipitates and matrix.

The chemical structure and morphology of carbonized bio-based materials are not yet understood. Various biomaterials have been utilized to prepare porous materials by carbonization, which is used for different environmental remediation applications, including air filtration and water treatment. In this work the effect of pyrolysis temperature (600–1000 °C, no oxygen-atmosphere) on chemical structure, porosity and morphology of date seeds was investigated. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) were used to study the changes in chemical compositions at the molecular level of the carbonized date seeds. The TOF-SIMS study revealed a complex mixture of compounds inhomogeneously distributed on the carbonized surface, and showed that fatty acids disappear quickly as a result of the heat-treatment. Both TOF-SIMS and XPS showed that metal oxides (especially potassium) accumulate during heating and the degree of aromaticity is observed to increase. The chemistry and morphology were shown (to some degree) to be controllable, which makes the material a promising candidate for developing a cheap porous adsorbent from date seeds.

Cornea, the outermost transparent layer of the eye, protects the eye from the external environment and maintains a proper vision. It is composed of three cellular layers, including the epithelium, 500 µm-thick stroma, and endothelium, separated from each other by two non-cellular collagen-based Bowman’s and Descemet’s membranes. The stroma represents ~90% of the cornea’s volume and constitutes a resilient collagen fibril-keratocyte architecture for the cornea ensuring optimal visual acuity. Untreated dysfunction of the cornea causes Fuch’s dystrophy, the dry eye syndrome, and keratitis that may lead to the blindness. The exploitation of modern in vitro and in vivo models for the corneal disease treatment suffers from experimental, ethical, and economical shortcomings, which necessitates developing human cornea-on-a-chip (CoC) devices allowing rapid and high-throughput sensing and drug screening. Comprised of 3D artificial biomaterial organoids or cultured biomaterial-human organ hybrids, well-defined modern lab-on-chips mimic molecular complexity, fluid dynamics, and physiological behaviour of real tissues or organs.

Here we present the photocrosslinking-based fabrication of a gelatin methacryloyl (GelMA) hydrogel lithographic CoC, and its analysis by time-of-flight secondary ion mass spectrometry (ToF-SIMS), as a benchmark for future studies involving seeded cells and drug diffusion in the hydrogel matrix. In the process, we compared 2D images, positive and negative SI mass spectra, and depth-profiles of GelMA hydrogel with ex vivo corneal sections, using typical collagen-derived species and keratocyte-membrane phospholipids as markers. ToF-SIMS of the GelMA hydrogel and the tissue confirmed the majority of NH^-, CN^-, CNO^-, C₃N^- and CH₂N⁺, CH₄N⁺, C₂H₄N⁺, C₂H₆N⁺, C₃H₆N⁺, C₄H₈N⁺, C₃H₈N⁺ in the samples. Moreover, the tissue spectra revealed signals of keratocyte plasma membrane-derived choline (C₅H₁₄NO⁺), phosphocholine (C₅H₁₅PNO₄⁺), phosphatidylcholine (C₄₀H₈₁NO₈P⁺), and fatty acids (C₁₆H₃₁O₂^‑, C₁₈H₃₃O₂^-, C₁₈H₃₅O₂^-). X-ray photoelectron spectroscopy measurements confirmed the atomic contents in artificial and native cornea samples, whereas atomic force microscopy imaging and nanoindentation studies revealed their broad ranges of elasticity (0.03-3 MPa), as expected from the literature data. Future ToF-SIMS experiments will involve in-chip seeded keratocytes as well as epi- and endothelial cells. Finally, off- and on-a-chip ToF-SIMS-based study of drug diffusion will be executed to validate the cornea-on-a-chip as an efficient model for high-throughput drug screening applications.

Anatase TiO₂ nanosheets synthesized via hydrothermal methods are cutting-edge materials with great potential for photocatalytic H₂ evolution.¹ Despite its potential, the wide optical bandgap and low catalytic activity of TiO₂ impede its performance.² Numerous studies have aimed to address these challenges, significantly enhancing its photocatalytic properties.³ In this work, we present an approach to further improve the photocatalytic H₂ production activity of anatase TiO₂ nanosheets by incorporating vanadium as a co-catalyst on the surface of TiO_2. The modified TiO₂ nanosheets were characterized by transmission electron microscopy, ToF-SIMS, and photoelectrochemical hydrogen evolution.

In the present study, we describe modifying the TiO₂ nanosheets by loading vanadium as a co-catalyst using a high-power sonochemical treatment to enhance the photocatalytic hydrogen reaction rates. The results of this study offer a novel approach to improve the efficiency of anatase TiO₂ nanosheets for photocatalytic H₂ evolution, with potential applications in renewable energy conversion and storage.

Keywords: Anatase TiO₂, photocatalytic H₂ evolution, co-catalyst, ToF-SIMS

References

[1] Hejazi, S., Mohajernia, S., Osuagwu, B., Zoppellaro, G., Andryskova, P., Tomanec, O., Kment, S., Zbořil, R., & Schmuki, P. (2020). On the Controlled Loading of Single Platinum Atoms as a Co-Catalyst on TiO₂ Anatase for Optimized Photocatalytic H₂ Generation. Advanced Materials, 32(16). https://doi.org/10.1002/adma.201908505

[2] Lee, K., Mazare, A., & Schmuki, P. (2014). One-dimensional titanium dioxide nanomaterials: nanotubes. Chemical Reviews, 114(19), 9385–9454. https://doi.org/10.1021/CR500061M

[3] Hejazi, S., Killian, M.S., Mazare, A., Mohajernia, S. (2022). Single-Atom-Based Catalysts for Photocatalytic Water Splitting on TiO₂ Nanostructures. Catalysts, 12, 905, https//doi.org/10.3390/catal12080905.

To realise their full functionality, many bacterial cells rely on the incorporation of metals on various levels of their cellular structure, which are associated with a wide variety of functions, ranging from S-layer formation and stability to cellular navigation. We use a combination of cryogenic scanning electron microscopy (SEM) and focused on beam (FIB) imaging with chemical analysis by time of flight secondary ion mass spectrometry (ToF-SIMS) to study the role of metals as well as small molecules in the context of bacterial cells, focusing on the examples of Caulobacter crescentus, whose S-layer stability crucially depends on the presence of calcium ions, and Magnetospirillium magneticum, which uses magnetosomes, membranous structures containing magnetite crystals, for orientation in the Earth’s magnetic field. As many cellular processes, for example regarding the cell’s life cycle, are associated with the presence of specific metal and small molecule ions, simultaneous spatial and chemical imaging in frozen cellular samples can provide insights into these mechanisms.

Digitally printed electronics are a driver for novel research in various fields owing to their design flexibility and other advantages such as expedited time-to-market. Ink-jetting of nano colloidal materials (also known as 0D materials), such as metal nanoparticles, semiconductor quantum dots, intrinsically conductive polymer colloids and graphene flakes have been successfully employed in applications ranging from wearable electronics to quantum optoelectronic devices and fully printed perovskite solar cells. However, the performance of printed devices can be lower than those made by traditional manufacturing methods and is not fully understood. Here we report on how SIMS is helping to understand inkjet-printed 0D materials and informing the development of novel formulations with enhanced performance.

We report that anisotropic electrical conductivity of printed silver nanoparticles (AgNPs) is caused by organic residues from their inks [1]. We used ToF-SIMS in combination with X-ray photoelectron spectroscopy (XPS) to show that the polymer stabiliser polyvinylpyrrolidone tends to concentrate between vertically stacked nanoparticle layers as well as at dielectric/conductive interfaces. Furthermore, highly mobile Ag ions generated in the presence of heat and applied electric fields are capable of diffusion, which has detrimental effect on the quality of the gate in Si/SiO₂-based devices. We have recently developed a gold NPs (AuNPs) conductive ink with the potential to overcome these limitations [2]. We employed a multifunctional thiol (TrisSH) in the ink to prevent the formation of microcracks and pores by mediating the cohesion of AuNPs via interaction between the thiol groups and the gold surface, which results in more uniform printed structures. The role of TrisSH as a cohesion enhancer is confirmed by OrbiSIMS and XPS.

All-inorganic perovskite nanocrystals (NCs) with enhanced environmental stability are of interest for optoelectronic applications. We report on the formulation of CsPbX3 (X is Br or I) inks for inkjet deposition and utilise these as photosensitive layers in graphene photodetectors [3]. We achieve a high photoresponsivity in the visible wavelength range and a spectral response controlled by the halide content of the perovskite. By utilising perovskite NCs, iGr and AuNPs, we fully inkjet-printed a photodetector with high performance explained by transfer of photo-generated charge carriers from the NCs into graphene and charge transport through the iGr network. ToF-SIMS Depth profiling revealed the presence of perovskites throughout the iGr layer.

The approaches developed here can be adopted for other 0D materials and enable in depth understanding of printed layers and interfaces, needed to unleash the potential of inkjet printing for fabrication of electronics and optoelectronics.

[1] G. F. Trindade et al., “Residual polymer stabiliser causes anisotropic electrical conductivity during inkjet printing of metal nanoparticles,” Commun. Mater., vol. 2, no. 1, pp. 1–10, 2021, doi: 10.1038/s43246-021-00151-0.

[2] J. Im et al., “Functionalized Gold Nanoparticles with a Cohesion Enhancer for Robust Flexible Electrodes,” ACS Appl. Nano Mater., vol. 5, no. 5, pp. 6708–6716, 2022, doi: 10.1021/acsanm.2c00742.

[3] J. S. Austin et al., “Photosensitisation of inkjet printed graphene with stable all-inorganic perovskite nanocrystals,” Nanoscale, vol. 15, no. 5, pp. 2134–2142, 2022, doi: 10.1039/d2nr06429d.