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Quantification of sulphur in copper metals by isotope dilution LA-ICP-MS using polyethylene frits
(2018)
Sulphur is one of the relevant impurities in copper and its alloys affecting their material properties. To ensure the quality of copper products, fast direct solid sampling techniques are very attractive. However, for the calibration suitable matrix reference materials are required. For the certification of such reference materials appropriate, SI-traceable analytical methods are essential. Therefore, a procedure was developed to quantify total sulphur in copper by combining the classical isotope dilution (ID) technique and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).
Here, for the first time, polyethylene (PE) frits were used to prepare appropriate solid samples for the sulphur quantification in copper metals (alloyed/unalloyed) by isotope dilution LA-ICP-MS. The properties of the PE frit meet the requirements as porous material with high absorption efficiency, thermal and chemical resistance as well as low sulphur blank. Different copper reference materials were used to develop and validate the procedure. The copper samples were spiked with 34S, digested with nitric acid and then the digests were absorbed on PE frits. After drying, the frits were analysed by LA-ICP-IDMS using a Nd:YAG laser at 213 nm coupled to an ICP sector field mass spectrometer. It could be demonstrated, that the sample solution dispersed on the frits did not influence the 32S/34S ratio significantly even though the sulphur intensities were fluctuating along the scanned lines. Relative standard deviations of the isotope ratios were below 5 % in average between three line scans (except for the pure spike solution and procedure blank). The measurement results were validated by comparing them with the results obtained by conventional ICP-IDMS after analyte-matrix separation. Plotting the mass fraction of sulphur in copper obtained by LA-ICP-IDMS versus those obtained by ICP-IDMS yields a linear curve with a correlation coefficient of 0.9999 showing a strong agreement between both techniques.
The metrological traceability to the SI from the kg down to the sulphur mass fraction in copper is established by an unbroken chain of comparisons, each accompanied by an uncertainty budget. Thus, the measurement results are considered reliable, acceptable and comparable within the stated measurement uncertainty.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is increasingly used to study the distribution of metal-containing drugs, imaging probes and nanomaterials in connection with disease related changes and therapy progress. Additionally, biomolecules can be detected indirectly by using metal-tagged antibodies.
The extracellular matrix (ECM) is, besides the cells, an important component of all body tissues. The macromolecular network of the ECM consists of structural proteins (e.g., collagen, elastin) and proteoglycans composed of highly negatively charged carbohydrates, the glycosaminoglycans (GAGs), which are covalently linked to a protein core. Many diseases, including inflammatory processes and tumors, are associated with characteristic ECM changes at an early stage. Recent studies have shown that contrast agents for magnetic resonance imaging (MRI), which are based on gadolinium containing chelate complexes or iron oxide nanoparticles, can bind themselves to ECM components.
To elucidate the role of GAGs like keratan sulfate (KS) and its modification state in disease, highly specific tools are necessary. As a complement to conventional immunohistochemistry LA-ICP-MS was applied to investigate the distribution of KS in tissue thin sections using a well characterized anti-KS antibody labelled with metal ions. Furthermore, LA-ICP-MS was used for the detection of MRI contrast agents and the identification of their target cells and molecules in tissue samples from animal models, e.g. for cardiovascular diseases. The results show the possibilities of LA-ICP-MS for the elucidation of pathological tissue changes.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is nowadays a versatile and powerful analytical method for direct solid sample analysis. The applicability has been demonstrated for a wide variety of samples covering hard and soft materials. In an imaging mode the technique provides quantitative information on the elemental distribution within a sample. LA-ICP-MS imaging is of particular interest in biomedical research as the distribution of an element gives valuable insight on uptake and distribution of essential and toxic trace elements, administered contrast agents as well es nanoparticles. LA-ICP-MS is therefore a powerful complement to other imaging techniques. Recent instrumental improvements, especially in sample chamber design, have contributed to better sensitivity and spatial resolution enabling subcellular imaging. The book chapter provides a comprehensive overview about spatially resolved localisation and quantification of various nanoparticles in cells and tissue thin sections by LA-ICP-MS. Furthermore, different sample preparation strategies and internal standardisation and calibration approaches for bioimaging by LA-ICP-MS are summarized and discussed.
Metal-containing nanomaterials are used in numerous fields ranging from industrial applications to nanomedicine. Several studies have demonstrated that the physicochemical properties of nanoparticles have an impact on their pharmacokinetics, transfer and clearance. The high sensitivity and multielement capability of LA-ICP-MS enables the elucidation of interactions between tissue components and nanomaterials used as imaging probes or drug carriers. Potential toxic effects are investigated as well. Thus, LA imaging significantly supports the clinical translation of safe and efficient nanoparticles for diagnostic and therapeutic purposes.
The interaction of nanoparticles (NPs) with cells has become a major field of interest, ranging from medical applications to nanotoxicology. Size, shape and surface modification of the NPs determine the uptake rate and pathway into the cells, and therefore impact specific cell components and processes.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is an established quantitative multi-elemental analysis and mapping technique. In recent years, it was shown that LA-ICP-MS can provide quantitative as well as distribution information of NPs in cell samples.
Here LA-ICP-MS was applied for the imaging of individual cells to study the uptake and intracellular processing of metal-containing nanostructures. Additionally, the local distribution of naturally occurring elements in cells like P was measured to indicate cell morphology. The cells were incubated with different types of NPs under varying experimental conditions. For LA analysis, the cells were fixed and dried.
Our findings show, that LA-ICP-MS is suitable for the localisation of nanoparticle aggregates within cellular compartments. The studied NPs accumulate in the perinuclear region in the course of intracellular processing, but do not enter the cell nucleus. The uptake efficiency depends strongly on the physicochemical properties of the nanostructures as well as on the incubation conditions like concentration and incubation time.
The results demonstrate the potential of LA-ICP-MS providing insight into NP uptake, intracellular distribution and cell-to-cell variation dependent on experimental parameters.
Nanoparticles (NPs) have found a wide range of applications in research and industry. Thereby the interaction of NPs with biological systems like cells has become a major field of interest, ranging from medical applications to nanotoxicology. Size, shape and surface modification of the nanomaterials determine the uptake rate and pathway into the cells, and therefore impact specific cell components and processes.
In recent years, elemental imaging of biological samples using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is gaining more and more importance. Improvements concerning both spatial resolution (down to 1 µm) and signal-to-background ratio due to low-dispersion LA chambers make LA-ICP-MS particularly interesting for single cell analysis.
Here LA-ICP-MS was applied for the imaging of individual cells to study the uptake and intracellular processing of metal-containing nanostructures. The cells were incubated with different NPs under varying experimental conditions and afterwards fixed with para-formaldehyde and dried for LA analysis. High-spatial resolution LA-ICP-MS was achieved by careful optimisation of the laser ablation parameters.
Our findings show, that LA-ICP-MS is applicable to localize NP aggregates within cellular compartments. The uptake efficiency depends strongly on the physicochemical properties of the nanostructures as well as on the incubation conditions like concentration and incubation time.
The results demonstrate the potential of LA-ICP-MS providing insight into nanoparticle-cell interaction dependent on experimental parameters.
Nanoparticles (NPs) have found a wide range of applications in research and industry. Thereby the interaction of NPs with biological systems like cells has become a major field of interest, ranging from medical applications to nanotoxicology. Size, shape and surface modification of the nanomaterials determine the uptake rate and pathway into the cells, and therefore impact specific cell components and processes.
Inductively coupled plasma mass spectrometry (ICP-MS) is a well-established analytical method offering high sensitivity and multi-element capability. By coupling a laser ablation (LA) system to an ICP-MS the analysis of different kinds of solid samples is possible. In recent years, it was shown that LA-ICP-MS can provide quantitative as well as distribution information of metal containing nanoparticles (NPs) in cell samples.
Here LA-ICP-MS was applied for the imaging of individual fibroblast cells to study the uptake and intracellular processing of NPs. Our results show that LA-ICP-MS can be used to localize nanoparticle aggregates within cellular compartments. The studied NPs accumulate in the perinuclear region in the course of intracellular processing, but do not enter the cell nucleus. The uptake efficiency depends strongly on the physico-chemical properties of the nanostructures as well as on the incubation conditions like concentration and incubation time.
ICP-MS was used to determine the composition of the nanomaterials as well as the number of NPs in cells after acid digestion of the samples.
In recent years, elemental imaging of biological samples like tissue thin sections using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is gaining more and more importance. Improvements concerning spatial resolution as well as signal-to-background ratio due to low-dispersion sample chambers make LA-ICP-MS also interesting for single cell analysis.
To evaluate the interaction of nanoparticles (NPs) with cells LA-ICP-MS was applied for the imaging of individual cells. Our findings show, that NP aggregates can be localized within cellular compartments. The uptake efficiency depends strongly on the physico-chemical properties of the nanostructures (size, chemical composition, surface modification), as well as on the incubation conditions (concentration, time).
Moreover, LA-ICP-MS is increasingly becoming an important complementary technique in bioanalysis by using element-tagging strategies to determine biomolecules indirectly. Based on the specific binding between antibodies and their corresponding antigens, proteins and peptides can be detected in tissue or cells using tagged antibodies. As artificial tags metal chelates loaded with lanthanides, polymer-based elemental tags or metal-containing nanoparticles can be used. Thereby LA-ICP-MS is a sensitive detection tool for multiplexed immuno-histochemistry of tissue and cell samples.
Our results demonstrate the potential of LA-ICP-MS to investigate the distribution of naturally occurring elements, administered agents as well as biomolecules by using metal-tagged antibodies.
Nanoparticles (NPs) have found a wide range of applications in research and industry. Thereby the interaction of NPs with biological systems like cells has become a major field of interest, ranging from medical applications to nanotoxicology. Size, shape and surface modification of the nanomaterials determine the uptake rate and pathway into the cells, and therefore impact specific cell components and processes.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is an established quantitative multi-elemental analysis and mapping technique. In recent years, it was shown that LA-ICP-MS can provide quantitative as well as distribution information of metal containing nanoparticles (NPs) in cell samples.
Here LA-ICP-MS was applied for the imaging of individual fibroblast cells to study the uptake and intracellular processing of NPs. Our results show that LA-ICP-MS can be used to localize nanoparticle aggregates within cellular compartments. The studied NPs accumulate in the perinuclear region in the course of intracellular processing, but do not enter the cell nucleus. The uptake efficiency depends strongly on the physico-chemical properties of the nanostructures as well as on the incubation conditions like concentration and incubation time.
ICP-MS was used to determine the composition of the nanomaterials as well as the number of NPs in cells after acid digestion of the samples.
Many current nanomaterials can serve as contrast agents in cellular or tissue imaging, drug delivery vehicles or therapeutics, whereas others can cause toxic effects. In order to evaluate nano-bio interactions, the number of nanoparticles (NPs) inside cells as well as their localisation within cellular substructures is of particular interest. The cellular uptake depends on the primary characteristics of the NPs (e.g. size, shape, surface coating) and on the cell type.
Laser ablation inductively coupled plasma mass spectrometry (LA‑ICP‑MS) is more and more used to study the NP pathway from uptake, via intracellular processing up to cell division. High-spatial resolution laser ablation at single cell level is achieved using novel low-dispersion LA chambers and by careful optimisation of laser energy, ablation frequency and scan speed at small laser spot sizes down to 1 µm. Different examples from BAM, Division 1.1 and cooperation partners using LA-ICP-MS to localize and quantify metal-containing nanoparticles are shown. The results demonstrate the potential of LA-ICP-MS providing insight into NP uptake, intracellular distribution and cell-to-cell variation.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is nowadays an established multi-elemental analysis and mapping technique. It was shown that LA-ICP-MS can visualize the elemental distribution within tissue thin sections or cell samples. Quantification is possible by using appropriate matrix-matched calibration samples. Besides naturally occurring elements and metals from contrast agents, biomolecules using metal-tagged antibodies were detected in different bio-medical samples. By combining the results with findings from histology, magnetic resonance imaging (MRI) and other techniques disease related changes like alterations of the extracellular matrix can be investigated.
Inductively coupled plasma-mass spectrometry (ICP-MS) is a well-established analytical method offering high sensitivity and multi-element analysis. ICP-MS has found acceptance in various application areas ranging from material analysis to applications in the life sciences. Within the last 15 years new strategies for the sensitive detection and accurate quantification of biomolecules in complex biomedical samples have been developed. Recent instrumental improvements have contributed to this progress.
As most of the biomolecules do not contain endogenous metals etectable with ICP-MS, bioconjugation with artificial metal-containing tags based on metal-loaded chelate complexes or nanoparticles is increasingly applied to determine biomolecules indirectly. Especially, the combination of immunohistochemical workflows using lanthanoid-tagged antibodies and ICP-MS detection provides new insights in the complexity and interdependency of cellular processes. Single-cell ICP-MS, also termed as mass cytometry, allows high-dimensional analysis of biomarkers in cell populations at single-cell resolution. For that purpose, lanthanoid isotope labelled antibodies are used to detect their corresponding target molecules. The visualisation of the elemental distribution is possible with laser ablation ICP-MS (LA-ICPMS) at high spatial resolution. Especially, the combination of LA with ICP time-of-flight mass spectrometry, also referred to as imaging mass cytometry (IMC), opens new possibilities for multiparametric tissue imaging at the single-cell level and even below. The lanthanoid localisation and concentration can be linked to their conjugated antibody target providing valuable information about surface markers, intracellular signalling molecules to measure biological function, and the network state of an individual cell in a tissue.
This book chapter focuses on new applications, where the multi-element capabilities of ICP-MS are used for the detection of lanthanoids applied as artificial elemental stains or tags for biomolecules and in particular antibodies.
The analytical potential of a nanosecond laser ablation inductively coupled plasma mass spectrometer (ns-LA-ICP-SFMS) system, equipped with an ultra-fast wash-out ablation chamber, is critically investigated for fast and highly spatially resolved (∼μm) qualitative elemental distribution within single cells. Initially, a low surface roughness (< 10 nm) thin In–SnO2 layer (total coating thickness ∼200 nm) deposited on glass is employed to investigate the size, morphology and overlapping of laser-induced craters obtained at different laser repetition rates, making use of Atomic Force Microscopy (AFM). Conical craters with a surface diameter of about 2 µm and depths of about 100 nm were measured after a single laser shot. Furthermore, the influence of the sampling distance (i.e. distance between the sample surface and the inner sniffer of the ablation chamber) on the LA-ICP-MS ion signal wash-out time is evaluated. A significant decrease of the transient 120Sn+ ion signal is noticed after slight variations (±200 μm) around the optimum sampling position. Ultra-fast wash-outs (< 10 ms) are achieved reducing the aerosol mixing from consecutive laser shots even when operating the laser at high repetition rates (25 – 100 Hz). Fast and highly spatially resolved images of elemental distribution within mouse embryonic fibroblast cells (NIH/3T3 fibroblast cells) and human cervical carcinoma cells (HeLa cells), incubated with gold nanoparticles (Au NPs) and Cd-based quantum dots (QDs), respectively, are determined at the optimized operating conditions. Elemental distribution of Au and Cd in single cells is achieved using a high scanning speed (50 µm/s) and high repetition rate (100 Hz). The results obtained for the distribution of fluorescent Cd-based QDs within the HeLa cells are in good agreement with those obtained by confocal microscopy. The size, morphology and overlapping of laser-induced craters in the fixed cells are also investigated using AFM, observing conical craters with a surface diameter of about 2.5 µm and depths of about 800 nm after a single laser shot.
Polyethylene (PE) frits were used to quantify sulphur in copper and its alloys by isotope dilution combined with LA-ICP-MS as an alternative approach to conventional sample preparation: the copper samples were spiked, the spiked samples were dissolved, the resulting solutions were absorbed in the PE frits and finally the PE frits were analysed by LA-ICP-MS. A prerequisite for such a support material is a low sulphur blank and thus PE was selected for this purpose. The absorption efficiency of the PE frits was studied for varying sulphur amounts ranging from 2 mg S to 80 mg S showing that more than 99.5% of the loaded sulphur was absorbed by the frit. The so prepared PE frits were measured by LA-ICP-MS and yielded a good linearity (R2 ¼ 0.999) for the sulphur ion intensities corresponding to sulphur amounts up to 40 mg S; the associated sensitivity is approximately 3.4 x 10⁴ cps μg⁻¹ for ³²S. For the validation of the developed procedure the reference materials BAM-M376a, BAM-228 and BAM-227 were applied such that 2 μg S, 5 μg S and 11 μg S were absorbed in the PE frits, respectively. These samples were pre-quantified for the adsorbed sulphur amount by external calibration LA-ICP-MS yielding sulphur amounts of 0.9 μg, 5.1 μg and 8.5 μg (quantified for ³²S only), respectively. Relative Standard deviations of the isotope ratios were below 5% in average (n ¼ 3 lines) in all cases (except for the pure spike solution). These samples were then analysed by LA-ICP-IDMS and the measurement results were validated by comparing them with the results obtained by conventional ICP-IDMS. The obtained relative expanded measurement uncertainties ranged between 10% and 26%. Pearson's coefficient was used to express the correlation between both techniques; the obtained value was 0.999 demonstrating a strong correlation. Contrary to most published LA-ICP-IDMS procedures, the developed procedure enables SI-traceability for the measurement results. The metrological traceability to the SI for the sulphur mass fractions in copper was established by an unbroken chain of comparisons, each accompanied by an uncertainty budget. Thus, the measurement results are considered reliable, acceptable and comparable within the stated measurement uncertainty. The metrological traceability chain from the kg down to mass fraction in the samples obtained by LA-ICP-IDMS is presented as well.
LA-ICP-MS is increasingly used for single cell analysis in two different detection modes using either the imaging mode with subcellular resolution or alternatively single spot analysis of cells with a larger laser spot size. This study compares the analytical figures of merit of both detection modes (signal to noise, precision, accuracy, throughput), as well as ease of operation and data evaluation. Adherent 3T3 fibroblast cells were stained with two metal dyes (mDOTA-Ho, Ir-DNA-intercalator) and several dozen cells were measured using both modes. We found a ten times higher throughput for single spot analysis, which has as well a straightforward data analysis, shortening the total analysis time further. The signal to noise ratio for single spot analysis was found to be slightly better compared to the signal to noise of pixels in imaging. The mean metal intensity per single cell differed by only 10% between both modes and obtained distributions were found to show no statistically significant differences. Using matrix matched calibration based on standards spotted onto nitrocellulose membrane, we achieved detection limits (10s) of 12 fg for Ir and 30 fg for Ho and quantified 57 +/-35 fg Ir and 1192 +/- 707 fg Ho per single cell.
Compared to a conventional ICP-MS measurement of a digest of about 60000 cells, 54% of Ir content and 358% Ho content was found using quantitative LA-ICP-MS. The difference might be a consequence of the two metal dyes binding to different structures of the cell and therefore might behave differently in sample preparation for conventional and LA-ICP-MS.
Inflammatory bowel diseases (IBD) comprise mainly ulcerative colitis (UC) and Crohn´s disease (CD). Both forms present with a chronic inflammation of the (gastro) intestinal tract, which induces excessive changes in the composition of the associated extracellular matrix (ECM). In UC, the inflammation is limited to the colon, whereas it can occur throughout the entire gastrointestinal tract in CD. Tools for early diagnosis of IBD are still very limited and highly invasive and measures for standardized evaluation of structural changes are scarce. To investigate an efficient non-invasive way of diagnosing intestinal inflammation and early changes of the ECM, very small superparamagnetic iron oxide nanoparticles (VSOPs) in magnetic resonance imaging (MRI) were applied in two mouse models of experimental colitis: the dextran sulfate sodium (DSS)-induced colitis and the transfer model of colitis. For further validation of ECM changes and inflammation, tissue sections were analyzed by immunohistochemistry. For in depth ex-vivo investigation of VSOPs localization within the tissue, Europium-doped VSOPs served to visualize the contrast agent by imaging mass cytometry (IMC). VSOPs accumulation in the inflamed colon wall of DSS-induced colitis mice was visualized in T2* weighted MRI scans. Components of the ECM, especially the hyaluronic acid content, were found to influence VSOPs binding. Using IMC, colocalization of VSOPs with macrophages and endothelial cells in colon tissue was shown. In contrast to the DSS model, colonic inflammation could not be visualized with VSOP-enhanced MRI in transfer colitis. VSOPs present a potential contrast agent for contrast-enhanced MRI to detect intestinal inflammation in mice at an early stage and in a less invasive manner depending on hyaluronic acid content.
Directing nanoparticles to the nucleus by attachment of nuclear localization sequences (NLS) is an aim in many applications. Gold nanoparticles modified with two different NLS were studied while crossing barriers of intact cells, including uptake, endosomal escape, and nuclear translocation. By imaging of the nanoparticles and by characterization of their molecular interactions with surface-enhanced Raman scattering (SERS), it is shown that nuclear translocation strongly depends on the particular incubation conditions. After an 1 h of incubation followed by a 24 h chase time, 14 nm gold particles carrying an adenoviral NLS are localized in endosomes, in the cytoplasm, and in the nucleus of fibroblast cells. In contrast, the cells display no nanoparticles in the cytoplasm or nucleus when continuously incubated with the nanoparticles for 24 h. The ultrastructural and spectroscopic data indicate different processing of NLS-functionalized particles in endosomes compared to unmodified particles. NLS functionalized nanoparticles form larger intraendosomal aggregates than unmodified gold nanoparticles. SERS spectra of cells with NLS-functionalized gold nanoparticles contain bands assigned to DNA and were clearly different from those with unmodified gold nanoparticles. The different processing in the presence of an NLS is influenced by a continuous exposure of the cells to nanoparticles and an ongoing nanoparticle uptake. This is supported by mass-spectrometry-based quantification that indicates enhanced uptake of NLS-functionalized nanoparticles compared to unmodified particles under the same conditions. The results contribute to the optimization of nanoparticle analysis in cells in a variety of applications, e.g., in theranostics, biotechnology, and bioanalytics.
An immunohistochemical method is described to visualize the distribution of metallothioneins 1/2 (MT 1/2) and metallothionein 3 (MT 3) in human ocular tissue. It is making use of (a) antibodies conjugated to gold nanoclusters (AuNCs) acting as labels, and (b) laser ablation (LA) coupled to inductively coupled plasma – mass spectrometry (ICP-MS).Water-soluble fluorescent AuNCs (with an average size of 2.7 nm) were synthesized and then conjugated to antibody by carbodiimide coupling. The surface of the modified AuNCs was then blocked with hydroxylamine to avoid nonspecific interactions with biological tissue. Immunoassays for MT 1/2 and MT 3 in ocular tissue sections (5 μm thick) from two post mortem human donors were performed. Imaging studies were then performed by fluorescence using confocal microscopy, and LA-ICP-MS was performed in the retina to measure the signal for gold. Signal amplification by the >500 gold atoms in each nanocluster allowed the antigens (MT 1/2 and MT 3) to be imaged by LA-ICP-MS using a laser spot size as small as 4 μm. The image patterns found in retina are in good agreement with those obtained by conventional fluorescence immunohistochemistry which was used as an established reference method.
An immunohistochemical method is described to visualize the distribution of metallothioneins 1/2 (MT 1/2) and metallothionein 3 (MT 3) in human ocular tissue. It is making use of (a) antibodies conjugated to gold nanoclusters (AuNCs) acting as labels, and (b) laser ablation (LA) coupled to inductively coupled plasma – mass spectrometry (ICP-MS). Water-soluble fluorescent AuNCs (with an average size of 2.7 nm) were synthesized and then conjugated to antibody by carbodiimide coupling. The surface of the modified AuNCs was then blocked with hydroxylamine to avoid nonspecific interactions with biological tissue. Immunoassays for MT 1/2 and MT 3 in ocular tissue sections (5 μm thick) from two post mortem human donors were performed. Imaging studies were then performed by fluorescence using confocal microscopy, and LA-ICP-MS was performed in the retina to measure the signal for gold. Signal amplification by the >500 gold atoms in each nanocluster allowed the antigens (MT 1/2 and MT 3) to be imaged by LA-ICP-MS using a laser spot size as small as 4 μm. The image patterns found in retina are in good agreement with those obtained by conventional fluorescence immunohistochemistry which was used as an established reference method.
Imaging Keratan Sulfate in Ocular Tissue Sections by Immunofluorescence Microscopy and LA-ICP-MS
(2022)
Carbohydrate-specific antibodies can serve as valuable tools to monitor alterations in the extracellular matrix resulting from pathologies. Here, the keratan sulfate-specific monoclonal antibody MZ15 was characterized in more detail by immunofluorescence microscopy as well as laser ablation ICP-MS using tissue cryosections and paraffin-embedded samples. Pretreatment with keratanase II prevented staining of samples and therefore demonstrated efficient enzymatic keratan sulfate degradation. Random fluorescent labeling and site-directed introduction of a metal cage into MZ15 were successful and allowed for a highly sensitive detection of the keratan sulfate landscape in the corneal stroma from rats and human tissue.
Nearly all disease processes are associated with variations of components of the extracellular matrix (ECM) that are typically observed during the development of inflammation. This concerns for example proteoglycans and their associated glycosaminoglycans (GAG), which have been shown to bind to cationic metal imaging probes due to their strong complexing activity. The complexing activity largely depends on the degree of GAG sulfation and/or carboxylation as well as on the GAG isomericity. In this central project, we investigate GAG structures from inflammatory disorders (namely cardiovascular diseases, inflammatory intestinal diseases and neuroinflammation) provided by researchers of the Collaborative Research Center at the molecular disaccharidic level using chromatographic and mass spectrometric methods. In parallel, the spatial localization and quantification of metal-based imaging probes are evaluated by LA-ICP-MS imaging.