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- 1.9 Chemische und optische Sensorik (70) (entfernen)
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Einer der aussichtsreichsten Ansätze, die Qualität und Sicherheit der gefertigten Teile in der metallbasierten additiven Fertigung (AM) zu erhöhen und die Notwendigkeit aufwändiger und zeitintensiver, zerstörender oder zerstörungsfreier Prüfungen (ZfP) nach der Fertigung zu verringern, liegt in dem Einsatz von in-situ Prozessüberwachungstechniken. Viele wichtige Prozessgrößen bei der additiven Fertigung sind thermischer Natur, wie z.B. die Temperatur des Schmelzbades. Aufgrund der Zugänglichkeit zum Werkstück während des Bauprozesses bieten sich optische Verfahren zur Temperaturbestimmung an. Für die Thermografie und Optische Emissionsspektrometrie im IR-Bereich, welche für die in-situ Anwendung prinzipiell als geeignet angesehen werden können, gibt es allerdings noch wenig konkrete praktische Umsetzungen, da die Möglichkeiten und individuellen Grenzen dieser Methoden, angewendet auf AM, noch nicht ausreichend erforscht sind. Aus diesem Grund verfolgt die BAM mit dem Projekt „Process Monitoring of AM“ (ProMoAM) im Themenfeld Material das Ziel, Verfahren des Prozessmonitorings zur in-situ Bewertung der Qualität additiv gefertigter Metallbauteile weiterzuentwickeln.
Im Beitrag wird der Fokus auf eine Versuchsserie gelegt, bei der Aufbau von Probekörpern aus dem austenitischen Edelstahl 316L mittels Laser-Pulver-Auftragschweißen (LPA) durch od. mit Hilfe von IR-Spektrometrie und Thermografie in-situ überwacht wurde. Hierbei stellen u.a. die hohe Bandbreite der zu messenden Temperaturen, die Bestimmung der Emissivität und ihre Änderung bei Phasenübergängen des Metalls große experimentelle Herausforderungen dar, wobei jede Methode individuelle Vor- und Nachteile aufweist, welche verglichen werden.
In the present paper the development of a semi-automated device for long-term monitoring of gaseous ammonia is described. A sensor material was produced that changes its optical properties in the pres-ence of low concentrations of ammonia in air. The implementation into an electronic device enables precise, simple, economic and fast monitoring of low concentrations of harmful gases, like ammonia, and hence can help to improve the climate monitoring in livestock housing, barns or stables.
We run two pilot LIP experiments in reactive gas mixtures. First, LIP is excited in BCl3 or BF3 plus H2 or CH4 to evaluate the efficiency of deposition of solid boron and boron carbide, materials that are largely used for refractory coatings. Second, we investigate a possibility of synthesis of fluorochlorosilanes SiFxCl4-x (x = 1, 2, 3) by LIP induced in SiF4+SiCl4 gas mixtures. Using fluorochlorosilanes with different combinations of F and Cl in the SiFxCly molecule may add flexibility in processes of silicon deposition and etching. The gases used and solid deposits are analyzed by optical emission spectroscopy (OES) and IR and mass spectrometry (MS). We also model the laser induced plasma by performing static equilibrium chemistry calculations to see whether desired reaction products are thermodynamically favorable and dynamic calculations of the expanding plasma plume to see how and where the products form.
Methods for the rapid and sensitive detection of target analytes are gaining importance in medical diagnostics and environmental monitoring, in the security, occupational health and safety as well as food sectors. Among all the methods employed for rapid tests, lateral flow assays (LFAs) are the most commonly used. However, some drawbacks are that most of these tests either indicate the analyte only indirectly, and in other cases the sensitivity is not high enough.
Keeping in mind these limitations, the use of stimuli-responsive materials for small-molecule sensing relying on chemical signal amplification and utilizing specific interactions between biomolecules such as antibodies and the corresponding analytes are particularly attractive. Such materials can also be incorporated on paper strips for lateral-flow assays in a straightforward manner. These sensing materials comprise mesoporous silica nanoparticles loaded with indicator molecules and containing certain hapten derivative molecules covalently grafted at the surface, which bind to the respective antibody and inhibit the release of a dye as reporter (Scheme 1). In presence of the designated analyte, a displacement of the antibody from the material is observed, allowing the release of dye. Because a large number of indicator molecules can be released when a single analyte molecule binds to an antibody cap, a strong signal amplification is observed.
Considering the modularity, high sensitivity and selectivity of these antibody-gated indicator delivery systems, the presentation discusses general aspects of system design as well as analytical performance and highlights the integration into a lateral-flow assay, showing as an example the determination of the explosives TATP, TNT and PETN with a fluorescence readout, in single-substance and multiplexing modes.
A possibility of deposition from laser-induced plasma (LIP) is investigated in search for an economic and simple method to obtain isotopic compounds from enriched gaseous precursors. A breakdown in mixtures of BCl3 and BCl3 with hydrogen, argon, and methane are studied both theoretically and experimentally. Calculations of expanding plasma of different composition are performed with the use of the fluid dynamic code coupled to the equilibrium chemistry solver. Condensed phases of boron, boron carbide, and graphite are predicted showing maximum concentrations in peripheral zones of the plasma.
In experiment LIP is induced in mixtures BCl3, Н2+BCl3, H2+Ar+BCl3, H2+BCl3+CH4, BF3, Н2+BF3, H2+Ar+BF3, and H2+Ar+BF3. The gases are analyzed before, during, and after laser irradiation by optical and mass spectroscopic methods. The composition of reaction products is found to be close to that predicted theoretically. The conversion of precursor gases BCl3 and BF3 into gaseous and condensed products is 100% for BCl3 and 80% for BF3. Solid deposits of up to 30 mg are obtained from all the reaction mixtures. FTIR analysis of BCl3+H2+CH4 deposits points to a presence of condensed boron and boron carbide that are also predicted by the model. Both calculations and preliminary experimental results suggest the chemical vapor deposition by LIP is promising for conversion of gaseous enriched precursors into elemental isotopes and their isotopic compounds.
Design, Synthesis and Characterization of Fluorescent MIP Particles for Labelling of Malignant Cells
(2020)
Cancer is a leading cause of death worldwide, and its early detection and resultant treatment contributes significantly to patient recovery and survival. Detection is currently based on magnetic resonance imaging and computed tomography, methods that are expensive, while processing of the results is time-consuming1. There is a need for low-cost cancer detection techniques that give conclusive results in the shortest time possible. When equipped with a reporter function, molecularly imprinted polymers (MIPs) targeting tumor markers on cancerous cells may provide a cheaper solution for imaging-based cancer detection. Thin MIP layers immobilized on particle platforms are ideal in this regard, because a fluorescence reporter can be integrated into the particle core and/or MIP shell and such core/shell nanoparticles show faster response times and increased selectivity in comparison to bulk MIPs.
Changes in sialylation patterns of cell surface glycans indicate malignancy2. Here, we present the design, synthesis and characterization of MIPs that target sialic acid-terminated glycans (SA MIPs), prepared as a thin layer on a polystyrene core/silica shell nanoparticle platform. The MIP particles contain fluorescent emitters and can be applied in fluorescence imaging of malignant tumors. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) are used for structural characterization. Binding capacity of the MIPs to target glycans and competing sugars is also evaluated and compared to that of the corresponding non-imprinted polymer particles (NIP).
The urgent necessity to carry out reliable and relevant analytical measurements directly at a point-of-need is one of the current drivers for the development of miniaturised analytical systems, quick tests and wearables. Despite their simplicity, this type of tests must guarantee analytical relevance and reliability like laboratory-based analysis, e.g., in terms of sensitivity, selectivity, immunity against false positives and false negatives as well as robustness and repeatability. Keeping in mind the high sensitivity offered by gated indicator-releasing micro- and nanoparticles due to their inherent features of signal amplification, we performed several optimisations to develop a potential biosensor platform for use in rapid tests. Conceptually, these gated materials are closely related to drug delivery systems, consisting of high porous materials usually closed with macromolecular “caps” and loaded with indicator molecules that are released in presence of a target analyte. However, the key difference between the two types of functional materials is that many drug delivery systems should deliver their cargo over a longer period, often many hours, whereas the gated materials prepared for sensing should show fast release kinetics, on the order of <5 min.
With the aim to optimise and adapt gated materials for sensing purposes, we prepared in this work several antibody-gated materials for small-molecule sensing. The materials consisted of porous silica particles containing indicator molecules in the pores and certain hapten molecules grafted to the particle surface close to the pore openings. The pores were then capped with antibodies binding to these haptens, thus inhibiting the escape of the indicators from inside of the pores. In presence of the corresponding analyte, the antibody is displaced from the surface of the material, allowing the escape of the indicators. This allows the detection of the analyte indirectly through an inherent signal amplification. In this work, the insecticide permethrin, a type-I pyrethroid, was selected as target model, because type-I pyrethroids play an important role in airplane disinfection. A first in-depth study of the various chemical tuning options of such antibody gated systems was performed. Different mesoporous silica supports, different functionalisation routes and different loading sequences were assessed. The materials’ performances were evaluated by studying their temporal response behaviour and detection sensitivity, including the tightness of pore closure (through the amount of blank release in absence of analyte) and the release kinetics. Our results indicate that the better the paratope-accommodating Fab region of the antibody “cap” fits into the host material’s pore openings, the better the closing/opening mechanism can be controlled. Because such materials can be used in various different formats from suspension assays[1] via microfluidic chips[2] to test strip-based lateral flow assays,[3] such materials present a powerful analytical particle platform for the sensitive analytics and diagnostics outside of a laboratory, realising sensitivities down to the µg kg–1 range in less analysis times of less than 5 min as we have recently demonstrated.[4]
This course will provide an introduction to plasma diagnostic techniques. The major focus of the course will be on the discussions of the practical procedures as well as the underlying physical principles for the measurements of plasma fundamental characteristics (e.g., temperatures, thermodynamic properties, and electron number density). Particular emphasis will be placed on inductively coupled plasma–atomic emission spectrometry, but other analytical plasmas will also be used as examples when appropriate. Selected examples on how one can manipulate the operating conditions of the plasma source, based on the results of plasma diagnostic measurements, to improve its performance used for spectrochemical analysis will also be covered. Topics to be covered include thermal equilibrium, line profiles, temperatures, electron densities, excitation processes, microreactions, pump and probe diagnostics, tomography, temporal and spatial resolution. Basis of plasma computer modeling will be presented.
Fluorescent molecularly imprinted polymers (MIPs) for sensing of phosphorylated protein epitopes
(2019)
Early detection of cancer is instrumental for successful therapeutic outcomes, but it is presently a considerable challenge. Biopsy of potentially cancerous tissues is the gold standard in medicine for the diagnosis and prognosis of this disease; however, it may not be possible in many cases due to tumour position or other complications. Liquid biopsy-based detection of specific cancer markers in biological fluids can be easily performed via immunoanalytical techniques. However, antibody-based methods suffer from high cost of tumour specific antibodies due to difficult and lengthy production. Furthermore, antibodies may have limited specificity to the target molecule, and limited lifetimes. The so-called “plastic antibodies” as MIPs can be a more affordable, reliable and stable alternative to antibodies, especially for cancer diagnostics.
Our goal is to create MIP particles to selectively bind cancer biomarkers and rapidly display a fluorescence change upon interaction with molecules of interest. Epitopes containing the phosphorylated tyrosine (pY) motif such as tripeptide YpYG and tetrapeptide pYEEI were selected as target analytes. Cancers may disrupt tyrosine phosphorylation processes regulated by human tyrosine kinases such as ZAP-70 and subsequently lead to a pronounced increase in pY residues on proteins. To ensure fast diffusion of analyte and rapid response core/shell silica micro- and nanoparticles with a thin polymer shell was chosen as the format for MIP synthesis. Fluorescent probe monomers consisting of fluorophore and recognition units are directly integrated in the polymer shell to obtain fluorescence response upon analyte binding.
We have synthesized the fluorescent MIP particles based on the previously published report for the novel phosphorylated targets with a high imprinting factor and high degree of discrimination between target analyte and non-phosphorylated and smaller competitors. The synthesized particles may be used in microfluidic devices for the rapid diagnostics of cancer.
Fluorescent molecularly imprinted polymers (MIPs) for sensing of phosphorylated protein epitopes
(2019)
Early detection of cancer is instrumental for successful therapeutic outcomes, but it is presently a considerable challenge. Biopsy of potentially cancerous tissues is the gold standard in medicine for the diagnosis and prognosis of this disease; however, it may not be possible in many cases due to tumour position or other complications. Liquid biopsy-based detection of specific cancer markers in biological fluids can be easily performed via immunoanalytical techniques. However, antibody-based methods suffer from high cost of tumour specific antibodies due to difficult and lengthy production. Furthermore, antibodies may have limited specificity to the target molecule, and limited lifetimes. The so-called “plastic antibodies” as MIPs can be a more affordable, reliable and stable alternative to antibodies, especially for cancer diagnostics.
Our goal is to create MIP particles to selectively bind cancer biomarkers and rapidly display a fluorescence change upon interaction with molecules of interest. Epitopes containing the phosphorylated tyrosine (pY) motif such as tripeptide YpYG and tetrapeptide pYEEI were selected as target analytes. Cancers may disrupt tyrosine phosphorylation processes regulated by human tyrosine kinases such as ZAP-70 and subsequently lead to a pronounced increase in pY residues on proteins. To ensure fast diffusion of analyte and rapid response core/shell silica micro- and nanoparticles with a thin polymer shell was chosen as the format for MIP synthesis. Fluorescent probe monomers consisting of fluorophore and recognition units are directly integrated in the polymer shell to obtain fluorescence response upon analyte binding.
We have synthesized the fluorescent MIP particles based on the previously published report [W. Wan et al., Chem. Eur. J., 2017, 23, 15974-1598] for the novel phosphorylated targets with a high imprinting factor and high degree of discrimination between target analyte and non-phosphorylated and smaller competitors. The synthesized particles may be used in microfluidic devices for the rapid diagnostics of cancer.
Asymmetrical laser-induced plasmas were investigated by a tomography approach based on the inverse Radon transform. Two distinct sources of asymmetricity were investigated: double-pulsed laser-induced plasmas in the orthogonal configuration and single-pulsed laser-induced plasmas under an inclined incidence angle. Both cases were observed at various delay times. The optical thinness of the laser-induced plasmas was achieved by appropriately adjusting the pulse energies. High temporal resolution is achieved by a gated intensified charge-coupled-device camera. The asymmetrical laser-induced plasmas are investigated in terms of their total emissivity, spectrally resolved emissivity, and temperature. The latter is obtained by the Saha–Boltzmann plot method. The images required for the inverse Radon transform technique were obtained with a high angular accuracy and reproducibility provided by mounting the spectrometer on a high-precision nano-positioning rotary stage. The plasmas were induced in the center of rotation of the stage. This arrangement allows the reconstruction of emissivity, which is integrated over a full spectral range (200-800 nm) or over a desired spectral range selected by a bandpass filter (~10 nm). It also allows for the reconstruction of spectrally-resolved emissivity in each cross sectional plasma slice by scanning the plasma across a spectrometer slit. The 3D maps of temperature and electron density are thus obtained for different types of asymmetric plasmas.
A goal of this work is to apply the model, which was initially developed for laser induced plasmas, to plasmas used in chemical reactors, in particular, the inductively-coupled-RF discharge plasma. The model predicts equilibrium chemical compositions of reaction mixtures as functions of plasma temperature and stoichiometry of reactants. The mixtures investigated are BCl3/H2/Ar and BF3/H2/Ar where Ar serves as the plasma-forming gas and H2 as a binding agent which binds the active species Cl and F and Cl- and F-containing intermediates to produce gaseous B and its condensate. An additional goal is to obtain information about intermediate reaction products for different ratios of BCl3/H2 and BF3/H2 and at different temperatures and different Ar flow rates. Also, chemical reactions in laser induced plasmas (LIPs) created on calcium hydrate and calcium carbonate targets in argon are modeled. The results are compared with those obtained by means of the equilibrium model based on the minimization of Gibbs free energy.
Molecule formation in calcium carbonate and calcium hydroxide libs plasmas: model and experiment
(2019)
Analysis of calcium hydrate and calcium carbonate samples and their mixtures is important for archeology, anthropology, and geology. Laser-induced plasma spectroscopy (LIBS) is a suitable tool for such the analysis as it allows for in- and on-line real time chemical assays. LIBS is inherently a technique for atomic analysis; however, since recently, it is also used for molecular analysis. The information attained by the latter is mainly related to “secondary” chemistry that deals with re-association of atoms and ions into molecules at long delay times (≥10 μs) after the initial breakdown. Even though the direct information about the initial molecular content in the target may be lost, the molecular analysis by LIBS can still be useful to assess the composition of samples.
In this work, chemical reactions in laser induced plasmas (LIPs) created on calcium hydrate and calcium carbonate targets in argon are modeled and compared to experiment. The model is based on the assumption that all ionization processes and chemical reactions are at local thermodynamic equilibrium. A chemical composition of argon-calcium-oxygen and argon-calcium-hydrogen plasmas is studied as a function of plasma temperature and pressure. It is established that more than twenty simple and composite molecules and ions can be formed in the course of chemical reactions. The results are compared with those obtained by means of the equilibrium model based on the minimization of Gibbs free energy.
A goal of this work is to apply the model, which was initially developed for laser induced plasmas, to plasmas used in chemical reactors, in particular, the inductively-coupled-RF discharge plasma. The model predicts equilibrium chemical compositions of reaction mixtures as functions of plasma temperature and stoichiometry of reactants. The mixtures investigated are BCl3/H2/Ar and BF3/H2/Ar where Ar serves as the plasma-forming gas and H2 as a binding agent which binds the active species Cl and F and Cl- and F-containing intermediates to produce gaseous B and its condensate. An additional goal is to obtain information about intermediate reaction products for different ratios of BCl3/H2 and BF3/H2 and at different temperatures and different Ar flow rates. Also, chemical reactions in laser induced plasmas (LIPs) created on calcium hydrate and calcium carbonate targets in argon are modeled. The results are compared with those obtained by means of the equilibrium model based on the minimization of Gibbs free energy.
Glycosylation is heavily altered in tumor cells compared with healthy cells, because of the different levels of expression of glycosyltransferases, glycosidases and monosaccharide transporters within a cancerous microenvironment. 1 Tumor-associated glycans, especially sialic acid (SA) conjugates, which are good candidates of tumor markers, can be used for Cancer early diagnosis. 2 However, studies on SA-binding lectins demonstrate that the type of SAlinkage and the glycosylation position of carbohydrate can greatly influence the affinity. 3 Therefore, there is a need for diagnostic tools owning high specificity and strong affinity to analyze and determine SA glycosylation motifs. 4 Herein, we report the development of fluorescent core/shell/shell nanoparticles where the outermost layer is a thin molecularly imprinted polymer (MIP) film binding to tumor cells in vitro by targeting cell surface SA. The core is made of N-doped red carbon nanodots (R-CNDs) which were prepared by hydrothermal synthesis, emitting intense red fluorescence under fluorescence microscopy imaging conditions. Silica coating of R-CNDs was achieved by a microemulsion method, resulting in ca. 40 nm large silica-coated CNDs (named R-CSNs).
Finally, a thin MIP-shell was accomplished by using a combination of non-fluorescent
monomer (3), functional monomers (1, 2) and cross-linker (EGDMA) for polymerization
(Figure 1). Transmission electron microscopy (TEM) is used for structural characterization of
the formation of MIP layer, and the results of cell-based binding tests show a promising binding
affinity of MIPs to tumor cells, allowing a relatively robust, specific and rapid analytical
method for cancer biopsies.
Spatial Heterodyne Spectroscopy (SHS) is a spectrometric technique that combines both dispersive and interferometric features into a customizable instrument. The Basis of SHS is a Michelson interferometer with its mirrors replaced by diffraction gratings and with no moving parts. The output signal from SHS is the interferogram, which is recorded with a 1D or 2D pixel array detector. The spatial periodicity of the fringes on the interferogram is a function of the wavelength of the diffracted light. Using the Fast Fourier Transform, the original optical spectrum that enters SHS is retrieved. The light that is analyzed by SHS can come from a variety of sources. In our work, we used Raman scattering and Laser-Induced Plasma to perform quantitative and qualitative analyses. Figure 1 compares the performance of the SHS with that of high Resolution echelle and portable low-resolution asymmetrically crossed Czerny-Turner spectrometers (OO in Fig.1). The analyzed light came from the plasma induced on a stainless-steel reference material. The SHS exhibits the resolution comparable to that of the echelle spectrometer used, about 8000. Due to a high throughput of the SHS (theoretically, ~200 times higher than that of grating instruments), the number of spectra needed to be accumulated for comparable signal-to-noise ratios is much smaller than in the case of the echelle and comparable to OO spectrometers.
Examples of Raman SHS applied to several pure liquids are given in Fig. 2. Raman SHS was used in three different settings: (i) for classification of six types of oils, (ii) for univariate/multivariate analysis of binary mixture cyclohexane-isopropanol, and (iii) for multivariate analysis of glycerol solution in water. For the last two settings, chemometric analysis of the spectra yielded linear calibration plots over the range 1-90% of concentrations of isopropanol in cyclohexane, and 0.5-10% of glycerol in water.
Chlorination of pool water and wastewater, in food and pharmaceutical production, as well as in pesticide and paper manufacturing is a routinely used technique. However, the amount of chlorine in water must be strictly adjusted, to ensure enough concentration to kill pathogenic bacteria and viruses, while preventing too high concentrations inducing negative effects on human health. As an indicator, a molecular fluorescent probe based on a BODIPY structure was designed. This indicator exhibits a sensitive and selective fluorescence response upon increasing concentrations of hypochlorite in aqueous solvent mixtures. Real-time analyses became possible after the integration of this fluorescent indicator into newly designed 2D & 3D microfluidic chips incorporating a passive sinusoidal mixer and a micro-hydrocyclone, respectively. A comparison of the two microfluidic systems, including their ability to prevent accumulation or circulation of microbubbles, has shown excellent fluidic behaviour for the micro-hydrocyclone device. This system was distinctly more robust against gas bubbles, showed a higher signal gain and allowed to halve the limit of detection to 0.02 mg L–1. The use of the 3D system to quantify the chlorine content of pool water samples for sensitive and quantitative chlorine monitoring has been demonstrated.
The Dark Side of Science
(2019)
The Joint Summer School of the two Marie Skłodowska-Curie Innovative Training Networks (ITN) “BioCapture” and “GlycoImaging”, funded by the EU within the Horizon 2020 framework programme, which are both devoted to the development of new methods for cancer biomarker and cancer cell detection, will take place at the Adlershof Campus of BAM. 19 Early stage researchers of both projects will convene, discuss their own science and plan future collaborative research. Training in scientific writing (instructor: Luita Spangler, Free University of Berlin), an employability workshop (Antti Kapanen, University of Applied Sciences Berlin) and first contacts with the “dark side of science” (Brian R. Pauw, BAM) will complement the programme of the summer school.