TY - JOUR A1 - Hülagü, Deniz A1 - Tobias, Charlie A1 - Climent Terol, Estela A1 - Gojani, Ardian A1 - Rurack, Knut A1 - Hodoroaba, Vasile-Dan T1 - Generalized Analysis Approach of the Profile Roughness by Electron Microscopy with the Example of Hierarchically Grown Polystyrene–Iron Oxide–Silica Core–Shell–Shell Particles N2 - The roughness as a property of core–shell (CS) microparticles plays a key role in their functionality. Quantitative evaluation of the roughness of CS microparticles is, however, a challenging task with approaches using electron microscopy images being scarce and showing pronounced differences in terms of methodology and results. This work presents a generalized method for the reliable roughness determination of nonplanar specimens such as CS particles from electron microscopic images, the method being robust and reproducible with a high accuracy. It involves a self-written software package (Python) that analyzes the recorded images, extracts corresponding data, and calculates the roughness based on the deviation of the identified contour. Images of single particles are taken by a dual mode scanning electron microscopy (SEM) setup which permits imaging of the same field-of-view of the sample with high resolution and surface sensitive in SE InLens mode as well as in transmission mode (TSEM). Herein, a new type of polystyrene core–iron oxide shell–silica shell particles is developed to serve as a set of lower micrometer-sized study objects with different surface roughness; the analysis of their images by the semiautomatic workflow is demonstrating that the particles’ profile roughness can be quantitatively obtained. KW - Core–shell particles KW - Image analysis KW - Nanoparticles KW - Roughness KW - SEM KW - transmission mode PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-542576 DO - https://doi.org/10.1002/adem.202101344 SP - 1 EP - 9 PB - Wiley-VCH AN - OPUS4-54257 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Giuseppe, Pignatelli A1 - Anne, Strasse A1 - Gumenyuk, Andrey A1 - Gornushkin, Igor B. T1 - Online monitoring of 3D printing of steel via optical emission spectroscopy N2 - Additive manufacturing by laser metal deposition (LMD) requires continuous online monitoring to ensure quality of printed parts. Optical emission spectroscopy (OES) is proposed for the online detection of printing defects by monitoring minute variations in the temperature of a printed spot during laser scan. A two-lens optical system is attached to a moving laser head and focused on a molten pool created on a substrate during LMD. The light emitted by the pool is collected by an ultraviolet–visible (UV–vis) spectrometer and processed. Two metrics are used to monitor variations in the surface temperature: the spectrally integrated emission intensity and correlation coefficient. The variations in the temperature are introduced by artificial defects, shallow grooves, and holes of various widths and diameters carved on a substrate surface. The metrics show sufficient sensitivity for revealing the surface defects, except for the smallest holes with an under-millimeter diameter. Additionally, numeric simulations are carried out for the detection of emission in the UV–vis and near-infrared (NIR) spectral ranges at various surface temperatures. It is concluded that both the metrics perform better in the NIR range. In general, this work demonstrates that spectrally resolved OES suits well for monitoring surface defects during 3D metal printing. KW - Process control KW - Additive manufacturing KW - Laser metal deposition KW - Optical emission spectroscopy KW - Optical sensor PY - 2022 DO - https://doi.org/10.1515/mt-2021-2082 VL - 64 IS - 1 SP - 24 EP - 32 PB - De Gruyter AN - OPUS4-54413 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gojani, Ardian T1 - Motion of an ensemble of magnetic microbeads in a microfluidic system N2 - This study describes the motion of magnetizable particles of spherical shape with radius at most of 1 μm, also referred to as microbeads, immersed in a liquid under laminar flow conditions in a microfluidic channel. An external magnetic field is applied in part of the system such that it permeates the channel and is characterized by a spatially varying magnetic field, i.e., the gradient of the magnetic field is nonzero. The beads are superparamagnetic; hence they can reach high level of magnetization in the presence of a magnetic field, and this magnetization disappears when the field is zero. Therein lies the attractiveness of these microbeads and the potential for applications because their motion can be controlled using an external magnetic field. The motion is governed by several factors, including the magnetic force acting on microbeads (particles), the drag force due to viscosity, the interaction between particles and the fluid, as well as the interaction between particles themselves. For a single particle case, the trajectory of the motion is determined by balancing the drag and magnetic forces acting on the particle, a calculation that in general requires numerical integration. For a system consisting of an ensemble of interacting particles, several regimes of motion dominated by one of the factors are identified. Of particular interest are the systems dominated by the large number of particles in the ensemble, i.e., high particle concentration, in which cases the wake influences the flow downstream. This effect is qualitatively investigated by considering the Navier-Stokes equation with and without the magnetic force contribution. T2 - 1st NIP Conference National Institute of Physics (IKF), the Albanian Academy of Sciences CY - Tirana, Albania DA - 10.02.2022 KW - MamaLoCA KW - Microfluidics KW - Magnetophoresis PY - 2022 AN - OPUS4-54366 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Beyer, S. A1 - Kimani, Martha Wamaitha A1 - Zhang, Y. A1 - Verhassel, A. A1 - Sternbæk, L. A1 - Wang, T. A1 - Persson, J. L. A1 - Härkönen, P. A1 - Johansson, E. A1 - Caraballo, R. A1 - Elofsson, M. A1 - Gawlitza, Kornelia A1 - Rurack, Knut A1 - Ohlsson, L. A1 - El-Schich, Z. A1 - Gjörloff Wingren, A. A1 - Stollenwerk, M. M. T1 - Fluorescent Molecularly Imprinted Polymer Layers against Sialic Acid on Silica-coated Polystyrene Cores - Assessment of the Binding Behavior to Cancer Cells N2 - Sialic acid (SA) is a monosaccharide usually linked to the terminus of glycan chains on the cell surface. It plays a crucial role in many biological processes, and hypersialylation is a common feature in cancer. Lectins are widely used to analyze the cell surface expression of SA. However, these protein molecules are usually expensive and easily denatured, which calls for the development of alternative glycan-specific receptors and cell imaging technologies. In this study, SA-imprinted fluorescent core-shell molecularly imprinted polymer particles (SA-MIPs) were employed to recognize SA on the cell surface of cancer cell lines. The SA-MIPs improved suspensibility and scattering properties compared with previously used core-shell SA-MIPs. Although SA-imprinting was performed using SA without preference for the alpha-2,3- and alpha-2,6-SA forms, we screened the cancer cell lines analyzed using the lectins Maackia Amurensis Lectin I (MAL I, alpha-2,3-SA) and Sambucus Nigra Lectin (SNA, alpha-2,6-SA). Our results show that the selected cancer cell lines in this study presented a varied binding behavior with the SA-MIPs. The binding pattern of the lectins was also demonstrated. Moreover, two different pentavalent SA conjugates were used to inhibit the binding of the SA-MIPs to breast, skin, and lung cancer cell lines, demonstrating the specificity of the SA-MIPs in both flow cytometry and confocal fluorescence microscopy. We concluded that the synthesized SA-MIPs might be a powerful future tool in the diagnostic analysis of various cancer cells. KW - Cancer KW - Imprinting KW - Molecularly imprinted polymers KW - SA conjugates KW - Sialic acid PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-546625 DO - https://doi.org/110.3390/cancers14081875 SN - 2072-6694 VL - 14 IS - 8 PB - MDPI CY - Basel AN - OPUS4-54662 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ecke, Alexander A1 - Bohm, Konrad A1 - Bell, Jérémy A1 - Schneider, Rudolf T1 - An Immunosensor for Pharmaceutical Contaminants in Water Supply N2 - Contamination of drinking water with pharmaceuticals is an emerging problem and a potential health threat. Immunochemical methods based on the binding of the analyte to specific antibodies enable fast & cost-effective on-site analyses. Magnetic bead-based immunoassays (MBBAs) allow for implementation into an immunosensor for online testing. Particles are prepared by either coupling the analyte molecule (diclofenac) or the respective antibody (amoxicillin) to the surface. For miniaturization, detection is performed electrochemically (chronoamperometry) on a microfluidic chip. The developed immunosensor will enable detection of pharmaceuticals directly in water supply pipes. T2 - Analytica Conference CY - München, Germany DA - 21.06.2022 KW - Immunosensor KW - Magnetic Particles KW - Microfluidics KW - Amperometry KW - Diclofenac KW - Amoxicillin PY - 2022 AN - OPUS4-55381 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hülagü, Deniz A1 - Tobias, Charlie A1 - Gojani, Ardian B. A1 - Rurack, Knut A1 - Hodoroaba, Vasile-Dan T1 - From 2D and Single Particle to 3D and Batch Analysis as a Routine Quality Check Procedure for the Morphological Characterization of Core-Shell Microparticles N2 - CS particles show unique properties by merging individual characteristics of the core and the shell materials. An alteration particularly in their surface roughness affects the final performance of the particles in the targeted application. Quantitative evaluation of the roughness of CS microparticles is, however, a challenging task employing microscopic techniques being scarce and showing large differences in terms of methodology and results. In our previous work, we have reported a systematic study with a reliable analysis tool, which evaluates profile roughness quantitatively, for individual core-shell microparticles using electron microscopy (EM) images of both types, Scanning Electron Microscopy (SEM) and transmission mode SEM (or TSEM). The SEM images contain two-dimensional (2D) information, therefore, provide profile roughness data only from the projection in the horizontal plane (in other words, from the “belly”) of a spherical particle. The present study offers a practical procedure to give access to more information by tilting the sample holder and hence allowing images of a single particle to be recorded at different orientations under the same view angle. From the analysis of these images, extended information on surface roughness of the particle can be extracted. Thus, instead of obtaining 2D information from a single SEM image, three-dimensional (3D) information is obtained from 2D projections recorded at different particle orientations. T2 - Microscopy and Microanalysis 2022 CY - Oregon, Portland, USA DA - 31.07.2022 KW - Core-shell particles KW - Image processing KW - Roughness KW - Scanning electron microscopy KW - Tilting PY - 2022 DO - https://doi.org/10.1017/S1431927622002094 SN - 1431-9276 VL - 28 IS - S1 SP - 332 EP - 334 PB - Cambridge University Press AN - OPUS4-55373 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Climent Terol, Estela A1 - Wan, Wei A1 - Rurack, Knut T1 - Toward Label-Free Optical Multiplexing of Analytes in Indicator Release Lateral Flow Assays via Detection Zones Containing Tailored Capture Materials N2 - The use of macromolecules and materials immobilized in the detection zone of test strips for indicator capture and focusing in label-free lateral flow assays (LFAs) is described, with emphasis on its future use in low number multiplexing. Several materials such as polyelectrolytes, functionalized mesoporous silica micro- and nanoparticles, chemically modified cellulose or glass fibre (GF) membranes and molecularly imprinted polymer gels coated onto membranes were studied in model assays, before the most promising materials were combined with antibody-gated indicator delivering (gAID) sensor materials. Cellulose, nitrocellulose and GF membranes were used as supports and highly fluorescent dyes of different charge states as model indicators. Combination of the best performing capture materials with gAID systems made it possible to distinctly increase the sensitivity and reduce the measurement uncertainty in the LFA testing of pentaerythritol tetranitrate (PETN) in aqueous samples. In addition, dual-plexing of PETN and 2,4,6-trinitrotoluene (TNT) was realized on a single test strip containing two dedicated capture zones. KW - Rapid tests KW - Vor-Ort-Analytik KW - Multiplexing KW - Teststreifen KW - Molecularly imprinted polymers PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-557873 DO - https://doi.org/10.1002/anse.202100062 VL - 2 IS - 4 SP - 1 EP - 10 PB - Wiley-VCH CY - Weinheim AN - OPUS4-55787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pérez-Padilla, Victor A1 - Burnage, Samual A1 - Valderrey, Virginia A1 - Gawlitza, Kornelia A1 - Rurack, Knut T1 - Fluorescence detection of perfluorocarboxylic acids with core-shell particles N2 - Perfluorocarboxylic acids (PFCAs) are a family of compounds that consist of a fully perfluorinated carbon backbone and a carboxylic acid moiety1. PFCAs have been classified as substances of very high concern by REACH regulations due to their persistence in the environment, non biodegradability and toxicological effects2. Thus, there is significant interest in detecting PFCAs in ground, waste, surface and drinking water. Fluorescence detection is a portable, easy-to-operate and cost-effective alternative, enabling the onsite detection of these analytes e.g., with miniaturized fluidic sensors. Here, a guanidine benzoxadiazole (BD) dye covalently attached to a polymerizable methacrylate unit was developed for the integration of the dye into polymers and on surfaces. The response behavior of the dye toward PFCAs was assessed in monophasic (EtOAc) and biphasic (EtOAc-H2O) solvent systems, the biphasic system being advantageous for the extraction of the hydrophobic organic acids from the aqueous phase. The BD dye was integrated into sensory silica core-polymer shell particles for the sensing of PFCAs directly in aqueous media. Submicron SiO2 particles were functionalized with 3 (trimethoxysilyl)propyl methacrylate followed by radical polymerization with the BD dye and ethylene glycol dimethacrylate. TEM images showed a homogeneous polymer shell with a thickness of 75±2 nm. By incorporating the BD dye into core-shell particles, lower limits of detection (1.52 µM for perfluorooctanoic acid, PFOA) were achieved if compared to the use of the neat BD dye in a biphasic assay (17.3 µM for PFOA), and excellent discrimination against inorganic acids thanks to the hydrophobic polymer shell. The particle sensory platform has proven to be an alternative for the sensing of PFCAs directly in water. T2 - 5th International Conference on Applied Surface Science (ICASS) 2022 CY - Palma de Mallorca, Spain DA - 25.04.2022 KW - PFOA KW - Emerging pollutants KW - Polymer nanolayers KW - Fluorescence detection KW - Guanidine benzoxadiazole KW - Core-shell particles PY - 2022 AN - OPUS4-56513 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pérez-Padilla, Victor A1 - Kimani, Martha Wamaitha A1 - Valderrey, Virginia A1 - Gawlitza, Kornelia A1 - Rurack, Knut T1 - Direct detection of glyphosate in water with fluorescent molecularly imprinted polymer particles N2 - Analysis of environmental contaminants such as pesticides is increasing in importance due to frequent detection of residues in water reserves and food stuff, as well as lowering of maximum residue levels (MRLs). Molecularly imprinted polymers (MIPs) have been developed for preconcentration of these analytes prior to analysis by chromatographic techniques [1]. MIPs are prepared by polymerization of monomers in a matrix containing the analyte, followed by extraction of the analyte to obtain binding sites that are complementary to the analyte of interest. Recently, our group developed MIPs containing fluorescent reporter molecules that can be used for direct detection and quantification of 2,4-D in contaminated water. Core/shell MIP particles were employed, consisting of sub-micron silica nanoparticles coated with a MIP shell containing a fluorescent reporter whose signal was enhanced upon binding with 2,4-D in water. A limit of detection of 20 nM was attained [2]. We present here a comparable system, composed of fluorescent core-shell MIPs for the direct analysis of pesticides in environmental samples. T2 - UK-Poland-Ukraine Bioinspired Materials Conference CY - Online meeting DA - 29.11.2022 KW - Core-Shell Particles KW - Fluorescent Probes KW - Molecularly Imprinted Polymers KW - Glyphosate KW - Guanidinium Receptors PY - 2022 AN - OPUS4-56514 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Garrido, E. A1 - Hernández-Sigüenza, G. A1 - Climent, Estela A1 - Marcos, M. D. A1 - Rurack, Knut A1 - Gaviña, P. A1 - Parra, M. A1 - Sancenón, F. A1 - Martí-Centelles, V. A1 - Martínez-Máñez, R. T1 - Strip-based lateral flow-type indicator displacement assay for γ-hydroxybutyric acid (GHB) detection in beverages N2 - The use of gamma-hydroxybutyric acid (GHB) in drug-facilitated sexual assault has increased due to its availability and high solubility in aqueous solutions and alcoholic beverages, necessitating the development of rapid methods for GHB detection. In this respect, portable testing methods for use in the field, based on lateral flow assays (LFAs) and capable of detecting trace concentrations of target analytes, are particularly attractive and hold enormous potential for the detection of illicit drugs. Using this strategy, here we report a rapid, low cost, easy-to-handle strip-based LFA for GHB analysis employing a smartphone for fluorescence readout. At molecular signalling level, the ensemble is based on a Cu2+ complex with a tetradentate ligand and the fluorescent dye coumarin 343, which indicate GHB through an indicator displacement assay (IDA) in aqueous solution. When incorporated in a LFA-based strip test this system shows a detection limit as low as 0.03 μM for GHB in MES buffer solution and is able to detect GHB at concentrations of 0.1 μM in soft drinks and alcoholic beverages in only 1 min. KW - Indicator displacement assay KW - Gamma-hydroxybutyric acid KW - Lateral flow assay KW - Test strip KW - Fluorescent dyes KW - Smartphone readout PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-564631 DO - https://doi.org/10.1016/j.snb.2022.133043 SN - 0925-4005 VL - 377 SP - 1 EP - 7 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-56463 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Climent Terol, Estela A1 - Weller, Michael G. A1 - Martínez-Mánez, R. A1 - Rurack, Knut T1 - Immunochemical design of antibody-gated indicator delivery (gAID) systems based on mesoporous silica nanoparticles N2 - In this work, the optimization of the immunochemical response of antibody-gated indicator delivery (gAID) systems prepared with mesoporous silica nanoparticles has been studied along various lines of system tailoring, targeting the peroxide-type explosive TATP as an exemplary analyte. The mechanism of detection of these gAID systems relies on a displacement of an antibody “cap” bound to hapten derivatives anchored to the surface of a porous hybrid material, allowing the indicator cargo stored in the mesopores to escape and massively amplify the analyte-related signal. Since our aim was to obtain gAID systems with the best possible response in terms of sensitivity, selectivity, and assay time, sera obtained from different immunization boosts were screened, the influence of auxiliary reagents was assessed, structural hapten modification (hapten heterology) was investigated, and various indicator dyes and host materials were tested. Considering that highly selective and sensitive immunological responses are best obtained with high-affinity antibodies which, however, could possess rather slow dissociation constants, leading to slow responses, the main challenge was to optimize the immunochemical recognition system for a rapid response while maintaining a high sensitivity and selectivity. The best performance was observed by grafting a slightly mismatching (heterologous) hapten to the surface of the nanoparticles in combination with high-affinity antibodies as “caps”, yielding for the first time gAID nanomaterials for which the response time could be improved from hours to <5 min. The materials showed favorable detection limits in the lower ppb range and discriminated TATP well against H2O2 and other explosives. Further optimization led to straightforward integration of the materials into a lateral flow assay without further treatment or conditioning of the test strips while still guaranteeing remarkably fast overall assay times. KW - Antibody-gated indicator delivery systems KW - Signal amplification KW - Immunochemical response optimization KW - Test strip analysis KW - TATP KW - Explosives detection KW - Heterologous hapten PY - 2022 DO - https://doi.org/10.1021/acsanm.1c03417 SN - 2574-0970 VL - 5 IS - 1 SP - 626 EP - 641 PB - American Chemical Society CY - Washington, DC AN - OPUS4-54176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -