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Statistic process control as well as process capability demand for calibrated determination of layer thicknesses in various industries, e.g. automotive, aerospace, microelectronics manufacturing. Calibration requires well know and well characterized samples. A calibration laboratory accredited according to DIN EN ISO 17025 has the objective to distribute standards traceable to SI units to industrial laboratories for quality control of manufacturing of various products. Especially, the thickness determination of thin metallic coatings e.g. from galvanic processes or layer deposition using X-Ray Fluorescence can be significantly improved by customized calibration samples. This is essential as the measurement uncertainty directly correlates to the capability performing reliable control of processes with high yield. For calibration laboratories, the validation of results using round robins and the direct comparison to national metrology institutes is a prerequisite to demonstrate the competence to perform calibration services.
In this paper a strategy to obtain traceability and validation for thin alloy layers as well as first results are presented. The combined use of the accredited method for determination of mass per area from measurement of mass and area combined with standard free X-Ray Fluorescence as well as chemical analysis of dissolved samples with thin layers is deployed for material systems as NixZn1-x as well as NixP1-x. The obtained results are compared to reference free X-Ray Fluorescence at the BESSY II laboratories of Physikalisch-Technische Bundesanstalt. An excellent agreement of the obtained measured values as mass per unit area and alloy concentrations from the different applied methods within the measurement uncertainty was observed for NixP1-x showing the successful performed traceability of the calibration samples to SI units in combination with a validation of results by national metrology institutes and the round robin approach.
Due to the increasing consumption of cereals worldwide, monitoring of growth, storage and processing is becoming more crucial. Particularly when stored, infested grains breed fungal clusters (“hot spots”) in which mycotoxins greatly exceed allowed maximum levels. Because of their unpredictable presence, current sampling and procedures for mycotoxin analysis are complex and contain invasive and cost intensive steps.
A possible approach to avoid sampling inaccuracies is the non-invasive analysis of the homogeneous gas phase above the crops, instead of analyzing random samples. However, this procedure requires microbial volatile organic compounds (MVOC´s) being released by the samples. Previous investigations revealed trichodiene to be a precursor in trichothecenes biosynthesis – one of the largest mycotoxin groups with more than 180 compounds. Due to its non-functionalized sesquiterpene structure, quantification of trichodiene using Headspace GC-MS methods is possible (e.g. [1]). Thereby, it could be used as biomarker for trichothecene contamination in foodstuff.
However, further studies are necessary. The correlation between trichodiene concentration in the gas phase and trichothecenes mass fraction in the sample must be examined closely to draw conclusions about the trichothecene content in samples. Realizing this idea, would widely extend the applicability of trichodiene and enormously simplify trichothecene quantification. Hence, this first step of an ongoing study aims to develop a laboratory reference method using trichodiene as volatile biomarker to quantify trichothecenes in cereals. Static headspace and SPME-enrichment coupled to gas chromatography with mass spectrometry (GC-MS) were employed. In a second step, this reference method is intended to validate new approaches for fast on-site screening of trichodiene in cereals.
Alternariol (AOH) and Alternariol monomethylether (AME) are two secondary metabolites of Alternaria fungi which can be found in various foodstuffs like tomatoes, nuts and grains. Due to their toxicity and potential mutagenic activity the need for the development of high-throughput methods for the supervision of AOH- and AME-levels is of increasing interest. As the availability of both native and labelled AOH and AME analytical standards is very limited we herein wish to present a novel concise approach towards their synthesis employing a ruthenium-catalyzed ortho-arylation4 as the key step.
Singlet oxygen generation potential of two novel free-base-porphyrin photocatalysts was investigated. The freebase-porphyrin-sensitized Fe3O4 magnetic nanoparticles (MNPs) were tested for the degradation of the model pollutant Bisphenol A (BPA) in aqueous solution, for the first time. MNPs with either cubic or spherical shape were synthesized using the sonochemical approach, followed by sensitizing with photoactive 4,4′,4′′,4′′′- (Porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid) (TCPP). The resulted photocatalysts were characterized in detail by scanning and transmission electron microscopy, Brunauer–Emmett–Teller analysis, spectral techniques and vibrating sample magnetometry. The electron spin resonance experiments have confirmed the high activity of the photocatalysts through the efficient formation of singlet oxygen in solution. The optimum operational parameters for BPA degradation were established as follows: 1.0 μmol L−1 BPA, 1.0 g L−1 of photocatalyst, 100 μmol L−1 H2O2, under UVA irradiation. In these conditions, the results for both photocatalysts revealed that after only 10 min of reaction, over 64% and ca. 90% of BPA have been removed from solution in the absence and presence of H2O2, respectively. Whereas after 60 minutes of treatment, only 24% of BPA in real wastewater effluent samples were removed under UVA irradiation in the absence of H2O2, showing the high complexity of real wastewater. Moreover, both photocatalysts were successfully used for BPA removal in three consecutive runs, without significant loss of catalytic features.
A novel technique based on laser induced plasma imaging is proposed to measure residual pressure in sealed containers with transparent walls, e.g. high voltage vacuum interrupter in this paper. The images of plasma plumes induced on a copper target at pressure of ambient air between 10−2Pa and 105Pa were acquired at delay times of 200ns, 400ns, 600ns and 800ns. All the plasma images at specific pressures and delay times showed a good repeatability. It was found that ambient gas pressure significantly affects plasma shape, plasma integral intensities and expansion dynamics. A subsection characteristic method was proposed to extract pressure values from plasma images. The method employed three metrics for identification of high, intermediate and low pressures: the distance between the target and plume center, the integral intensity of the plume, and the lateral size of the plume, correspondingly. The accuracy of the method was estimated to be within 15% of nominal values in the entire pressure range between 10−2Pa and 105Pa. The pressure values can be easily extracted from plasma images in the whole pressure range, thus making laser induced plasma imaging a promising technique for gauge-free pressure detection.
Many applications of nanomaterials in the life sciences require the controlled functionalization of these materials with ligands like polyethylene glycol (PEG) and/or biomolecules such as peptides, proteins, and DNA. This enables to tune their hydrophilicity and biocompatibility, minimize unspecific interactions, improve biofunctionalization efficiencies, and enhance blood circulation times. Moreover, it is the ultimate prerequisite for their use as reporters in assays or the design of targeted optial probes for bioimaging. At the core of these functionalization strategies are reliable and validated methods for surface group and ligand quantification that can be preferably performed with routine laboratory instrumentation, require only small amounts of substances, and are suitable for many different types of nanomaterials.
We present here versatile and simple concepts for the quantification of common functional groups, ligands, and biomolecules on different types of organic and inorganic nano-materials, using different types of optical reporters and method validation with the aid of multimodal reporters, method comparisons, and mass balances.
Polymer nanoparticles (NPs) are of increasing importance for a wide range of applications in the material and life sciences. This includes their application as carriers for e.g., analyte-responsive ligands for DNA sequencing platforms, drugs as well as dye molecules for use as multichromophoric reporters for signal enhancement in optical assays or the fabrication of nanosensors and targeted probes in bioimaging studies. All these applications require surface functionalization of the particles with e.g., ligands, sensor dyes, or analyte recognition moieties like biomolecules, and subsequently, the knowledge of the chemical nature and total number of surface groups as well as the number of groups accessible for coupling reactions. Particularly attractive for the latter are optically active reporters together with sensitive and fast optical assays, which can be read out with simple, inexpensive instrumentation.
We assessed a variety of conventional and newly developed colorimetric and fluorometric labels for optical surface group analysis, utilizing e.g., changes in intensity and/or color for signal generation. Moreover, novel cleavable and multimodal reporters were developed which consist of a reactive group, a cleavable linker, and an optically active moiety, chosen to contain also heteroatoms for straightforward method validation by elemental analysis, ICP-OES, ICP-MS or NMR. In contrast to conventional labels measured bound at the particle surface, which can favor signal distortions by scattering and encoding dyes, cleavable reporters can be detected colorimetrically or fluorometrically both attached at the particle surface and after quantitative cleavage of the linker in the transparent supernatant after particle removal e.g., by centrifugation. Here, we present first results obtained for the optical quantification of carboxylic and amino groups on a series of self-made polystyrene NPs with different types of labels and compare their potential and drawbacks for surface group analysis.
To keep up with emerging mycotoxins and their transformation products fast and reliable toxicity tests are needed. Toxicity testing of mycotoxins is carried out usually by performing in vitro assays or is evaluated by using laboratory animals like mice, rats or chicken in in vivo studies.
Settled between classical in vitro approaches and in vivo studies with higher animals are tests with the nematode Caenorhabditis elegans. Since Sydney Brenner described 1974 the cultivation and handling of C. elegans, this worm is widely used as model organism in developmental biology and neurology. Due to many benefits like easy and cheap cultivation, a completely sequenced genome and short generation time, it also plays an important role in toxicological research. Finally, the high number of conserved genes between human and C. elegans make the worm an ideal candidate for toxicological investigations.
In this study we used C. elegans to assess the toxic effects of the relevant food mycotoxin citrinin (CIT), the mycoestrogen zearalenone (ZEN) and the modified mycotoxin ZEN-14-sulfate (ZEN-14-S) on different lifetable parameters including reproduction, thermal and oxidative stress tolerance and lifespan. All tested mycotoxins significantly decreased the amount of offspring. In case of ZEN and CIT also significant negative effects on stress tolerance and lifespan were observed compared to the control group.
Moreover, metabolization of mycotoxins in the worms was investigated by using LC MS/MS. Extraction of the worms treated 5 days with mycotoxin-containing and UVC-killed bacteria showed metabolization of ZEN to α-ZEL and β-ZEL (ZEL = zearalenol, ratio about 3:2). ZEN 14-S was reduced to ZEL 14-S and CIT was metabolized to mono hydroxylated CIT.
An overview about different analytical approaches will be presented of how to detect metals in individual biological cells by use of ICP-MS. For this purpose, we are using different sample introduction systems for ICP-MS for detection, imaging and quantification of metals at cellular levels.
By use of laser ablation, we have studied the up-take by and distribution of nanoparticles in single cells. Recently we have developed staining techniques to measure protein and DNA content of cells and identifying the cell status by immunoassays using metal-tagging of antibodies. New research based on cell arrays will be shortly discussed.
Using pneumatic nebulization and microdroplet generation, we have also studied the up-take of nanoparticles and toxic metals as well as essential elements in single cells using different ICP-MS mass spectrometric concepts (sector field instrument, triple-quad instrument, time of flight (CyTOF) instrument).
The different ICP-MS based methods will be compared concerning their analytical figures of merit and their strengths and weaknesses will be evaluated.
We are using LA-ICP-MS to quantify metals in biological cells and thin cuts of tissues from varies organs. Different applications will be presented to demonstrate the state of the art of bioimaging to visualize the elemental distribution pattern in soft bio-materials (tissue, single cells) of metals, metal containing stains and metal-tagged antibodies. For this purpose, different strategies for metal tagging will be presented and will be compared in terms of analytical figures of merit. First applications for detection of biomarkers in animal and human tissue samples will be presented.
In a first example, we have applied LA-ICP-MS to visualize the local distribution of proteins, which are used as bio-markers for neurodegenerative diseases. For this purpose, brain tissues from mice experiments have been stained by metal-tagged antibodies. House-keeping proteins have been investigated as internal cellular standards. Additionally, ink-jet printing of metal doped inks onto the surface of tissue samples has been applied for drift corrections and quantification. Validation of our results are achieved in comparison to immune-histochemical staining and optical microscopy.
In a second example, we used specific metal-tagged antibodies for detection of biomarker specific for prostate cancer. For this purpose, micro tissue arrays are incubated with metal-tagged antibodies for bioimaging of samples from many patients using simultaneous detection of all relevant biomarkers and their tags.
For improvement of sensitivity in the next example application nanoparticle tagged antibodies for detection of metallothionines in eye lens tissue samples will be discussed.
Recently we have used our tagging and staining strategies to determine the cell cycle of single cells, which is of future interest for toxicological studies.
Finally, future trends in elemental microscopy and mass cytometry imaging will be discussed.
Laser tissue soldering (LTS) based on indocyanine green (ICG)-mediated heat- denaturation of proteins might be a promising alternative technique for micro-suturing, but up to now the Problem of too weak shear strength of the solder welds in comparison to sutures is not solved. Earlier reports gave promising results showing that solder supported by carrier materials can enhance the cohesive strength of the liquid solder. In these studies, the solder was applied to the carriers by dip coating. Higher reliability of the connection between the solder and the carrier material is expected when the solder is bound covalently to the carrier material. In the present study a poly(ether imide) (PEI) membrane served as carrier material and ICG- supplemented albumin as solder substrate. The latter was covalently coupled to the carrier membrane under physiological conditions to prevent structural protein changes. As laser source a diode continuous-wave laser emitting at 808 nm with intensities between 250mW and 1500mW was utilized. The Albumin functionalized carrier membrane was placed onto the tunica media of explanted pig thoracic aortae forming an overlapping area of approximately 0.5×0.5 cm2. All tests were performed in a dry state to prevent laser light absorption by water. Infrared spectroscopy, spectro-photometrical determination of the secondary and Primary amine groups after acid orange II staining, contact angle measurements, and atomic force microscopy proved the successful functionalization of the PEI membrane with albumin. A laser power of 450mW LTS could generate a membrane-blood vessel connection which was characterized by a shear strength of 0.08±0.002MPa, corresponding to 15% of the tensile strength of the native blood vessel. Theoretically, an overlapping zone of 4.1mmaround the entire circumference of the blood vessel could have provided shear strength of the PEI membrane-blood vessel compound identical to the tensile strength of the native blood vessel. These in-vitro results confirmed the beneficial effects of solder reinforcement by carrier membranes, and suggest LTS with covalently bound solders on PEI substrates for further studies in animal models.
Imaging of Eu doped very small iron oxide nanoparticle in atherosclerotic plaques via LA ICP-MS
(2018)
Atherosclerotic lesions can be visualized by magnetic resonance imaging (MRI) using very small iron oxide nanoparticles (VSOP). VSOP accumulate in atherosclerotic plaques and thus serve as an atherosclerosis probe.
The aim of this project was to image the distribution of europium doped VSOP (Eu-VSOP) by laser ablation ICP-MS in histological thin cuts of the aortic root region of ApoE knockout mouse model that is rich in atherosclerotic plaques. In addition, it was investigated whether VSOP accumulation in the plaques correlates with other biomarkers of inflammation for example macrophages and altered endothelium to assess whether it correlates with instability or vulnerability of the plaque regions. For this purpose, antibodies were labeled with various lanthanide elements and correlated with the Eu-VSOP distribution using LA-ICP-MS in a multiplex measurement mode.
A possible correlation of reactive oxygen species (ROS) with endogenous iron or Eu-VSOP can also be detected by LA-ICP-MS. For this purpose, ROS-specific antibodies were also labeled with lanthanides.
The overall interest in nanotoxicity, triggered by the increasing use of nanomaterials in the material and life sciences, and the synthesis of an ever increasing number of new functional nanoparticles calls for standardized test procedures and for efficient approaches to screen the potential genotoxicity of these materials. Aiming at the development of fast and easy to use, automated microscopic methods for the determination of the genotoxicity of different types of nanoparticles, we assess the potential of the fluorometric γH2AX assay for this purpose. This assay, which can be run on an automated microscopic detection system, relies on the detection of DNA double strand breaks (DSB) as a sign for genotoxicity. Here, we provide first results obtained with broadly used nanomaterials like CdSe/CdS and InP/ZnS quantum dots as well as iron oxide, gold, and polymer particles of different surface chemistry with previously tested colloidal stability and different cell lines like Hep-2 and 8E11 cells, which reveal a dependence of the genotoxicity on the chemical composition as well as the surface chemistry of these nanomaterials. These studies will be also used to establish nanomaterials as positive and negative genotoxicity controls or standards for assay performance validation for users of this fluorometric genotoxicity assay. In the future, after proper validation, this microscopic platform technology will be expanded to other typical toxicity assays.
Imaging of Eu doped very small iron oxide nanoparticle in atherosclerotic plaques via LA-ICP-MS
(2018)
Atherosclerotic lesions can be visualized by magnetic resonance imaging (MRI) using very small iron oxide nanoparticles (VSOP). VSOP accumulate in atherosclerotic plaques and thus serve as an atherosclerosis probe. The aim of this project was to image the distribution of europium doped VSOP (Eu-VSOP) by laser ablation ICP-MS in histological thin cuts of the aortic root region of ApoE knockout mouse model that is rich in atherosclerotic plaques. In addition, it was investigated whether VSOP accumulation in the plaques correlates with other biomarkers of inflammation for example macrophages and altered endothelium to assess whether it correlates with instability or vulnerability of the plaque regions. For this purpose, antibodies were labeled with various lanthanide elements and correlated with the Eu-VSOP distribution using LA-ICP-MS in a multiplex measurement mode.
Ternary semiconductors quantum dots (t-QD) are Cd-free nanocrystals made from I-III-VI group elements like silver or copper, indium and sulfide yielding CIS (CuInS2) or AIS (AgInS2) QDs. They are interesting alternatives to Cd-based QDs for applications as solar concentrators or optically active material for solar cells, light emitting diodes (LED) or reporters for diagnostic assays.
To avoid ligand exchange procedures for high quality QDs, commonly synthesized in high boiling apolar solvents with apolar surface ligands, AIS QDs are synthesized in aqueous solution, required for bioanalytical application, by a microwave-assisted procedure. The surface of these QDs is passivated by a ZnS shell to enhance photoluminescence quantum yield (PL QY) and prevent material decomposition and oxidation. The resulting AIS/ZnS QDs exhibit broad PL spectra in the visible and near infrared, tunable by size and chemical composition.
I will show the simple synthetic procedure and a spectroscopic study of different AIS QDs evaluating their PL properties and stability, PL QY, and PL decay kinetics. The analyzed sample showed long lifetimes, relatively high QY (50%) and good stability. Ligand conjugation is also performed to allow the embedding in polymer matrix, which requires apolar cappng.
The simple aqueous synthesis together with the tunable emission color, the high PL QY, the high absorption coefficients and the long luminescence lifetimes make these t-QDs promising Cd-free materials for many different applications in the material and life sciences.
The recently reported luminescent chromium(III) complex 13+ ([Cr(ddpd)2]3+; ddpd=N,N’-dimethyl-N,N’-dipyridine-2-yl-pyridine-2,6-diamine) shows exceptionally strong near-IR emission at 775 nm in water under ambient conditions (F=11%) with a microsecond lifetime as the ligand design in 13+ effectively eliminates non-radiative decay pathways, such as photosubstitution, back-intersystem crossing, and trigonal twists. In the absence of energy acceptors, such as dioxygen, the remaining decay pathways are energy transfer to high energy solvent and ligand oscillators, namely OH and CH stretching vibrations. Selective deuteration of the solvents and the ddpd ligands probes the efficiency of these oscillators in the excited state deactivation. Addressing these energytransfer pathways in the first and second coordination sphere furnishes a record 30% quantum yield and a 2.3 millisecond lifetime for a metal complex with an earth-abundant metal ion in solution at room temperature. The combined fundamental insights will pave the way for selective design strategies in the field of luminescent complexes with earth-abundant metal ions.
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.
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.
The aim of this work is to investigate the Synthesis of core-shell upconverting nanoparticles (UCNP).
The UCNP are coated with a Gold Shell to plasmonically enhance the fluorescence emision. The distance between the UCNP core and the plasmonic structure is tuned by the aid of a silica at different Shell thicknesses.
Phage display is used to find specific target binding peptides for polypropylene (PP) surfaces. PP is one of the most commonly used plastics in the world. Millions of tons are produced every year. PP binders are of particular interest because so far gluing or printing on PP is challenging due to its low surface energy. A phage display protocol for PP was developed followed by Next Generation DNA Sequencing of the whole phage library. Data analysis of millions of sequences yields promising peptide candidates which were synthesized as PEG conjugates. Fluorescence-based adsorption-elution-experiments show high adsorption on PP for several sequences.