From microtiter plates to droplets - there and back again. - In: Micromachines, ISSN 2072-666X, Bd. 13 (2022), 7, 1022, S. 1-13
Droplet-based microfluidic screening techniques can benefit from interfacing established microtiter plate-based screening and sample management workflows. Interfacing tools are required both for loading preconfigured microtiter-plate (MTP)-based sample collections into droplets and for dispensing the used droplets samples back into MTPs for subsequent storage or further processing. Here, we present a collection of Digital Microfluidic Pipetting Tips (DMPTs) with integrated facilities for droplet generation and manipulation together with a robotic system for its operation. This combination serves as a bidirectional sampling interface for sample transfer from wells into droplets (w2d) and vice versa droplets into wells (d2w). The DMPT were designed to fit into 96-deep-well MTPs and prepared from glass by means of microsystems technology. The aspirated samples are converted into the channel-confined droplets’ sequences separated by an immiscible carrier medium. To comply with the demands of dose-response assays, up to three additional assay compound solutions can be added to the sample droplets. To enable different procedural assay protocols, four different DMPT variants were made. In this way, droplet series with gradually changing composition can be generated for, e.g., 2D screening purposes. The developed DMPT and their common fluidic connector are described here. To handle the opposite transfer d2w, a robotic transfer system was set up and is described briefly.
Microtoxicology by microfluidic instrumentation: a review. - In: Lab on a chip, ISSN 1473-0189, (2022), insges. 24 S.
Microtoxicology is concerned with the toxic effects of small amounts of substances. This review paper discusses the application of small amounts of noxious substances for toxicological investigation in small volumes. The vigorous development of miniaturized methods in microfluidics over the last two decades involves chip-based devices, micro droplet-based procedures, and the use of micro-segmented flow for microtoxicological studies. The studies have shown that the microfluidic approach is particularly valuable for highly parallelized and combinatorial dose-response screenings. Accurate dosing and mixing of effector substances in large numbers of microcompartments supplies detailed data of dose-response functions by highly concentration-resolved assays and allows evaluation of stochastic responses in case of small separated cell ensembles and single cell experiments. The investigations demonstrate that very different biological targets can be studied using miniaturized approaches, among them bacteria, eukaryotic microorganisms, cell cultures from tissues of multicellular organisms, stem cells, and early embryonic states. Cultivation and effector exposure tests can be performed in small volumes over weeks and months, confirming that the microfluicial strategy is also applicable for slow-growing organisms. Here, the state of the art of miniaturized toxicology, particularly for studying antibiotic susceptibility, drug toxicity testing in the miniaturized system like organ-on-chip, environmental toxicology, and the characterization of combinatorial effects by two and multi-dimensional screenings, is discussed. Additionally, this review points out the practical limitations of the microtoxicology platform and discusses perspectives on future opportunities and challenges.
Automated analysis of acetaminophen toxicity on 3D HepaRG cell culture in microbioreactor. - In: Bioengineering, ISSN 2306-5354, Bd. 9 (2022), 5, 196, S. 1-16
Real-time monitoring of bioanalytes in organotypic cell cultivation devices is a major research challenge in establishing stand-alone diagnostic systems. Presently, no general technical facility is available that offers a plug-in system for bioanalytics in diversely available organotypic culture models. Therefore, each analytical device has to be tuned according to the microfluidic and interface environment of the 3D in vitro system. Herein, we report the design and function of a 3D automated culture and analysis device (3D-ACAD) which actively perfuses a custom-made 3D microbioreactor, samples the culture medium and simultaneously performs capillary-based flow ELISA. A microstructured MatriGrid® has been explored as a 3D scaffold for culturing HepaRG cells, with albumin investigated as a bioanalytical marker using flow ELISA. We investigated the effect of acetaminophen (APAP) on the albumin secretion of HepaRG cells over 96 h and compared this with the albumin secretion of 2D monolayer HepaRG cultures. Automated on-line monitoring of albumin secretion in the 3D in vitro mode revealed that the application of hepatotoxic drug-like APAP results in decreased albumin secretion. Furthermore, a higher sensitivity of the HepaRG cell culture in the automated 3D-ACAD system to APAP was observed compared to HepaRG cells cultivated as a monolayer. The results support the use of the 3D-ACAD model as a stand-alone device, working in real time and capable of analyzing the condition of the cell culture by measuring a functional analyte. Information obtained from our system is compared with conventional cell culture and plate ELISA, the results of which are presented herein.
Stationary, continuous, and sequential surface-enhanced raman scattering sensing based on the nanoscale and microscale polymer-metal composite sensor particles through microfluidics: a review. - In: Advanced optical materials, ISSN 2195-1071, Bd. 10 (2022), 7, 2102757, S. 1-25
Surface-enhanced Raman scattering (SERS) is a label-free and accurate analytical technique for the detection of a broad range of various analytes such as, biomolecules, pesticides, petrochemicals, as well as, cellular and other biological systems. A key component for the SERS analysis is the substrate which is required to be equipped with plasmonic features of metal nanostructures that directly interact with light and targeted analytes. Either metal nanoparticles can be deposited on the solid support (glass or silicon) which is suitable for stationary SERS analysis or dispersed in the solution (freely moving nanoparticles). Besides these routinely utilizing SERS substrates, polymer-metal composite particles are promising for sustained SERS analysis where metal nanoparticles act as plasmon-active (hence SERS-active) components and polymer particles act as support to the metal nanoparticles. Composite sensor particles provide 3D interaction possibilities for analytes, suitable for stationary, continuous, and sequential analysis, and they are reusable/regenerated. Therefore, this review is focused on the experimental procedures for the development of multiscale, uniform, and reproducible composite sensor particles together with their application for SERS analysis. The microfluidic reaction technique is highly versatile in the production of uniform and size-tunable composite particles, as well as, for conducting SERS analysis.
General background of SERS sensing and perspectives on polymer-supported plasmon-active multiscale and hierarchical sensor particles. - In: Advanced optical materials, ISSN 2195-1071, Bd. 10 (2022), 4, 2102001, S. 1-27
Surface-enhanced Raman scattering (SERS) is one of the most powerful analytical techniques for the identification of molecules. The substrate, on which SERS is dependent, contains regions of nanoscale gaps (hotspots) that hold the ability to concentrate incident electromagnetic fields and effectively amplify vibrational scattering signals of adsorbed analytes. While surface plasmon resonance from metal nanostructures is a central focus for the SERS effect, the support of polymers can be significantly advantageous to provide larger exposure of structured metal surfaces for efficient interactions with analytes. Characteristics of the polymer particles such as softness, flexibility, swellability, porosity, optical transparency, metal-loading ability, and high surface area can allow diffusion of analytes and penetrating light deeply that can enormously amplify sensing outcomes. As polymer-supported plasmon-active sensor particles can emerge as versatile SERS substrates, the microfluidic platform is promising for the generation of sensor particles as well as for performing sequential SERS analysis of multiple analytes. Therefore, in this perspective article, the development of multifunctional polymer-metal composite particles, and their applications as potential sensors for SERS sensing through microfluidics are presented. A detailed background from the beginning of the SERS field and perspectives for the multifunctional sensor particles for efficient SERS sensing are provided.
Vaccination, immunity and breakthrough: quantitative effects in individual immune responses illustrated by a simple kinetic model. - In: Applied Sciences, ISSN 2076-3417, Bd. 12 (2022), 1, 31, insges. 15 S.
The personal risks of infection, as well as the conditions for achieving herd immunity, are strongly dependent on an individual’s response to the infective agents on the one hand, and the individual’s reactions to vaccination on the other hand. The main goal of this work is to illustrate the importance of quantitative individual effects for disease risk in a simple way. The applied model was able to illustrate the quantitative effects, in the cases of different individual reactions, after exposition to viruses or bacteria and vaccines. The model was based on simple kinetic equations for stimulation of antibody production using different concentrations of the infective agent, vaccine and antibodies. It gave a qualitative explanation for the individual differences in breakthrough risks and different requirements concerning a second, third or further vaccinations, reconsidering different efficiencies of the stimulation of an immune reaction.
Shape-dependent catalytic activity of gold and bimetallic nanoparticles in the reduction of methylene blue by sodium borohydride. - In: Catalysts, ISSN 2073-4344, Bd. 11 (2021), 12, 1442, S. 1-20
In this study the catalytic activity of different gold and bimetallic nanoparticle solutions towards the reduction of methylene blue by sodium borohydride as a model reaction is investigated. By utilizing differently shaped gold nanoparticles, i.e., spheres, cubes, prisms and rods as well as bimetallic gold–palladium and gold-platinum core-shell nanorods, we evaluate the effect of the catalyst surface area as available gold surface area, the shape of the nanoparticles and the impact of added secondary metals in case of bimetallic nanorods. We track the reaction by UV/Vis measurements in the range of 190-850 nm every 60 s. It is assumed that the gold nanoparticles do not only act as a unit transferring electrons from sodium borohydride towards methylene blue but can promote the electron transfer upon plasmonic excitation. By testing different particle shapes, we could indeed demonstrate an effect of the particle shape by excluding the impact of surface area and/or surface ligands. All nanoparticle solutions showed a higher methylene blue turnover than their reference, whereby gold nanoprisms exhibited 100% turnover as no further methylene blue absorption peak was detected. The reaction rate constant k was also determined and revealed overall quicker reactions when gold or bimetallic nanoparticles were added as a catalyst, and again these were highest for nanoprisms. Furthermore, when comparing gold and bimetallic nanorods, it could be shown that through the addition of the catalytically active second metal platinum or palladium, the dye turnover was accelerated and degradation rate constants were higher compared to those of pure gold nanorods. The results explore the catalytic activity of nanoparticles, and assist in exploring further catalytic applications.
Textured and hierarchically constructed polymer micro- and nanoparticles. - In: Applied Sciences, ISSN 2076-3417, Bd. 11 (2021), 21, 10421, insges. 17 S.
Microfluidic techniques allow for the tailored construction of specific microparticles, which are becoming increasingly interesting and relevant. Here, using a microfluidic hole-plate-device and thermal-initiated free radical polymerization, submicrometer polymer particles with a highly textured surface were synthesized. Two types of monomers were applied: (1) methylmethacrylate (MMA) combined with crosslinkers and (2) divinylbenzene (DVB). Surface texture and morphology can be influenced by a series of parameters such as the monomer-crosslinker-solvent composition, surfactants, and additives. Generally, the most structured surfaces with the simultaneously most uniform particles were obtained in the DVB-toluene-nonionic-tensides system. In a second approach, poly-MMA (PMMA) particles were used to build aggregates with bigger polymer particles. For this purpose, tripropyleneglycolediacrylate (TPGDA) particles were synthesized in a microfluidic co-flow arrangement and polymerized by light- irradiation. Then, PMMA particles were assembled at their surface. In a third step, these composites were dispersed in an aqueous acrylamide-methylenebisacrylamide solution, which again was run through a co-flow-device and photopolymerized. As such, entities consisting of particles of three different size ranges - typically 0.7/30/600 [my]m - were obtained. The particles synthesized by both approaches are potentially suitable for loading with or incorporation of analytic probes or catalysts such as dyes or metals.
Micro flow photochemical synthesis of Ca-sensitive fluorescent sensor particles. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 21 (2021), 8/9, S. 518-526
Fluorescence probes have widely been used for detecting and imaging Ca2+-enriched parts of cells but more rarely for quantitative determination of concentrations. In this study we show how this can be achieved by a novel approach using hydrogel particles. In a microfluidic co-flow arrangement spherical droplets were generated from an aqueous solution of acrylamide, N,N'-methylenebisacrylamide crosslinker and photoinitiator and subsequently photo-cured in situ yielding gel particles in a sub millimeter range. These particles were separated, dried under reduced pressure and re-swollen in water containing Rhod-5N tri potassium salt as calcium ion selective fluorescence probe. After that the particles were dried again and stored for further investigations. Upon exposure of dried particles to calcium chloride solutions they swell and take up Ca2+-ions forming a strong fluorescing complex with Rhod-5N. Thus, fluorescence intensity increases with calcium ion concentration. Up to ca. 0.50 mM the enhancement effect is strong and then becomes considerably weaker. The intensity-concentration-dependence is well described by an equation derived from the equilibrium of the formation of a 1:1 Ca2+:Rhod-5N complex. The particles allow for a fast optical determination of Ca2+-concentrations up to 0.50 mM in analyte volumes down to below 10 [my]L.
Metal nanoparticles as free-floating electrodes. - In: Encyclopedia, ISSN 2673-8392, Bd. 1 (2021), 3, S. 551-565
Colloidal metal nanoparticles in an electrolyte environment are not only electrically charged but also electrochemically active objects. They have the typical character of metal electrodes with ongoing charge transfer processes on the metal/liquid interface. This picture is valid for the equilibrium state and also during the formation, growth, aggregation or dissolution of nanoparticles. This behavior can be understood in analogy to macroscopic mixed-electrode systems with a free-floating potential, which is determined by the competition between anodic and cathodic partial processes. In contrast to macroscopic electrodes, the small size of nanoparticles is responsible for significant effects of low numbers of elementary charges and for self-polarization effects as they are known from molecular systems, for example. The electrical properties of nanoparticles can be estimated by basic electrochemical equations. Reconsidering these fundamentals, the assembly behavior, the formation of nonspherical assemblies of nanoparticles and the growth and the corrosion behavior of metal nanoparticles, as well as the formation of core/shell particles, branched structures and particle networks, can be understood. The consequences of electrochemical behavior, charging and self-polarization for particle growth, shape formation and particle/particle interaction are discussed.
Challenges for nanotechnology. - In: Encyclopedia, ISSN 2673-8392, Bd. 1 (2021), 3, S. 618-631
The term "Nanotechnology" describes a large field of scientific and technical activities dealing with objects and technical components with small dimensions. Typically, bodies that are in-at least-two dimensions smaller than 0.1 [my]m are regarded as "nanobjects". By this definition, a lot of advanced materials, as well as the advanced electronic devices, are objects of nanotechnology. In addition, many aspects of molecular biotechnology as well as macromolecular and supermolecular chemistry and nanoparticle techniques are summarized under "nanotechnology". Despite this size-oriented definition, nanotechnology is dealing with physics and chemistry as well as with the realization of technical functions in the area between very small bodies and single particles and molecules. This includes the shift from classical physics into the quantum world of small molecules and low numbers or single elementary particles. Besides the already established fields of nanotechnology, there is a big expectation about technical progress and solution to essential economic, medical, and ecological problems by means of nanotechnology. Nanotechnology can only meet these expectations if fundamental progress behind the recent state of the art can be achieved. Therefore, very important challenges for nanotechnology are discussed here.
Microfluidically supported characterization of responses of Rhodococcus erythropolis strains isolated from different soils on Cu-, Ni-, and Co-stress. - In: Brazilian journal of microbiology, ISSN 1678-4405, Bd. 52 (2021), 3, S. 1405-1415
We present a new methodological approach for the assessment of the susceptibility of Rhodococcus erythropolis strains from specific sampling sites in response to increasing heavy metal concentration (Cu2+, Ni2+, and Co2+) using the droplet-based microfluid technique. All isolates belong to the species R. erythropolis identified by Sanger sequencing of the 16S rRNA. The tiny step-wise variation of metal concentrations from zero to the lower mM range in 500 nL droplets not only provided accurate data for critical metal ion concentrations but also resulted in a detailed visualization of the concentration-dependent response of bacterial growth and autofluorescence activity. As a result, some of the isolates showed similar characteristics in heavy metal tolerance against Cu2+, Ni2+, and Co2+. However, significantly different heavy metal tolerances were found for other strains. Surprisingly, samples from the surface soil of ancient copper mining areas supplied mostly strains with a moderate sensitivity to Cu2+, Ni2+, and Co2+, but in contrast, a soil sample from an excavation site of a medieval city that had been covered for about eight centuries showed an extremely high tolerance against cobalt ion (up to 36 mM). The differences among the strains not only may be regarded as results of adaptation to the different environmental conditions faced by the strains in nature but also seem to be related to ancient human activities and temporal partial decoupling of soil elements from the surface. This investigation confirmed that microfluidic screening offers empirical characterization of properties from same species which has been isolated from sites known to have different human activities in the past.
Tuning the morphology of bimetallic gold-platinum nanorods in a microflow synthesis. - In: Colloids and surfaces, Bd. 626 (2021), 127085
An automated microfluidic system with computer-controlled syringe pumps was applied for screening a three-dimensional concentration space for the formation of binary gold-platinum metal nanorods. Leveraging the micro segmented flow technique, precise residence and reactant addition timings as well as concentration spaces were addressed. The density and thickness of quasi-isotropic platinum shells on gold nanorod cores were tuned from isolated spots to a dense arrangement of high-aspect-ratio columns. The changing optical properties of the particles in the platinum deposition were used for monitoring the reaction progress and the products by the means of a fiber based micro flow-through spectrophotometer allowing to optimize process times. From our data, we propose an electrochemical model, postulating a diode-like effect and limitations for the formation of Pt nuclei on the gold surface and the formation of nano local elements. This point of view is supported by the observed decoration effects of gold facets and to the formation of columnar structures of the platinum shell.
Softness meets with brightness: dye-doped multifunctional fluorescent polymer particles via microfluidics for labeling. - In: Advanced optical materials, ISSN 2195-1071, Bd. 9 (2021), 13, 2002219, insges. 22 S.
Fluorogenic labeling strategies have emerged as powerful tools for in vivo and in vitro imaging applications for diagnostic and theranostic purposes. Free organic chromophores (fluorescent dyes) are bright but rapidly degrade. Inorganic nanoparticles (e.g., quantum dots) are photostable but toxic to biological systems. Alternatively, dye-doped polymer particles are promising for labeling and imaging due to their properties that overcome limitations of photodegradation and toxicity. This progress report, therefore, presents various synthesis techniques for the generation of dye-doped fluorescent polymer particles. Polymer particles are relatively soft compared to inorganic nanoparticles and can be synthesized with characteristics like biocompatibility and stimuli responsiveness. Also, their ability of loading fluorophores through various interactions reveals brightness. Here, a multiscale-multicolor library of bright and soft fluorescent polymer particles is generated hierarchically. Various microfluidic supported strategies have been applied where fluorophores can be linked to polymeric networks noncovalently and covalently in the interior, and at the surface of nanoparticles (60-550 nm). Besides, microfluidic strategies for hydrophilic and hydrophobic fluorescent polymer microparticles (20-800 [my]m) have been performed for systematic tuning in size and color combination. Furthermore, soft and bright particulate assemblies are enabled through interfacial interactions at the intermediate scale (600 nm-3 [my]m) between the nanometer and micrometer lengthscale.
Extremophiles in soil communities of former copper mining sites of the East Harz region (Germany) reflected by re-analyzed 16S rRNA data. - In: Microorganisms, ISSN 2076-2607, Bd. 9 (2021), 7, 1422, insges. 16 S.
The east and southeast rim of Harz mountains (Germany) are marked by a high density of former copper mining places dating back from the late 20th century to the middle age. A set of 18 soil samples from pre- and early industrial mining places and one sample from an industrial mine dump have been selected for investigation by 16S rRNA and compared with six samples from non-mining areas. Although most of the soil samples from the old mines show pH values around 7, RNA profiling reflects many operational taxonomical units (OTUs) belonging to acidophilic genera. For some of these OTUs, similarities were found with their abundances in the comparative samples, while others show significant differences. In addition to pH-dependent bacteria, thermophilic, psychrophilic, and halophilic types were observed. Among these OTUs, several DNA sequences are related to bacteria which are reported to show the ability to metabolize special substrates. Some OTUs absent in comparative samples from limestone substrates, among them Thaumarchaeota were present in the soil group from ancient mines with pH > 7. In contrast, acidophilic types have been found in a sample from a copper slag deposit, e.g., the polymer degrading bacterium Granulicella and Acidicaldus, which is thermophilic, too. Soil samples of the group of pre-industrial mines supplied some less abundant, interesting OTUs as the polymer-degrading Povalibacter and the halophilic Lewinella and Halobacteriovorax. A particularly high number of bacteria (OTUs) which had not been detected in other samples were found at an industrial copper mine dump, among them many halophilic and psychrophilic types. In summary, the results show that soil samples from the ancient copper mining places contain soil bacterial communities that could be a promising source in the search for microorganisms with valuable metabolic capabilities.
Electrostatic control of Au nanorod formation in automated microsegmented flow synthesis. - In: ACS applied nano materials, ISSN 2574-0970, Bd. 4 (2021), 2, S. 1411-1419
An automated flow rate program was applied for the synthesis of gold nanorods of different aspect ratios dependent on a two-dimensional concentration space of reducing agent and additional silver ions. It was found a regular redshift of the spectral position of the electromagnetic in-axis resonance of metal nanorods with decreasing concentration of reducing agent and increasing concentration of silver ions. The increase of resonance wavelength is strongly correlated with the aspect ratio of the formed nanorods. The experimental results agree with an electrostatic model of self-polarization due to positive excess charge of the nanorods in the presence of CTAB and confirm the crucial role of electrostatic control in the formation of nonspherical and composed nanoparticles in general.
Reclassification of Haloactinobacterium glacieicola as Occultella glacieicola gen. nov., comb. nov., of Haloactinobacterium album as Ruania alba comb. nov, with an emended description of the genus Ruania, recognition that the genus names Haloactinobacterium and Ruania are heterotypic synonyms and description of Occultella aeris sp. nov., a halotolerant isolate from surface soil sampled at an ancient copper smelter. - In: International journal of systematic and evolutionary microbiology, ISSN 1466-5034, Bd. 71 (2021), 4, 004769
In the course of screening the surface soils of ancient copper mines and smelters (East Harz, Germany) an aerobic, non-motile and halotolerant actinobacterium forming small rods or cocci was isolated. The strain designated F300T developed creamy to yellow colonies on tryptone soy agar and grew optimally at 28 ˚C, pH 7-8 and with 0.5-2% (m/v) NaCl. Its peptidoglycan was of type A4α l-Lys-l-Glu (A11.54). The menaquinone profile was dominated by MK-8(II, III-H4) and contained minor amounts of MK-8(H2), MK-8(H6) and MK-9(H4). The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, mono and diacylated phosphatidylinositol dimannosides, and components that were not fully characterized, including two phospholipids, two glycolipids and an uncharacterized lipid. Major whole-cell sugars were rhamnose and ribose. The fatty acid profile contained mainly iso and anteiso branched fatty acids (anteiso-C15:0, iso-C14:0) and aldehydes/dimethylacetals (i.e. not fatty acids). Sequence analysis of its genomic DNA and subsequent analysis of the data placed the isolate in the group currently defined by members of the genera Ruania and Haloactinobacterium (family Ruaniaceae , order Micrococcales ) as a sister taxon to the previously described species Haloactinobacterium glacieicola , sharing an average nucleotide identity and average amino acid identity values of 85.3 and 85.7%, respectively. Genotypic and chemotaxonomic analyses support the view that strain F300T (=DSM 108350T=CIP 111667T) is the type strain of a new genus and new species for which the name Occultella aeris gen. nov., sp. nov. is proposed. Based on revised chemotaxonomic and additional genome based data, it is necessary to discuss and evaluate the results in the light of the classification and nomenclature of members of the family Ruaniaceae , i.e. the genera Haloactinobacterium and Ruania . Consequently, the reclassification of Haloactinobacterium glacieicola as Occultella glacieicola comb. nov. and Haloactinobacterium album as Ruania alba comb. nov., with an emended description of the genus Ruania are proposed.,
Hierarchical assemblies of polymer particles through tailored interfaces and controllable interfacial interactions. - In: Advanced functional materials, ISSN 1616-3028, Bd. 31 (2021), 9, 2007407, insges. 22 S.
Hierarchical assembly architectures of functional polymer particles are promising because of their physicochemical and surface properties for multi-labeling and sensing to catalysis and biomedical applications. While polymer nanoparticles' interior is mainly made up of the cross-linked network, their surface can be tailored with soft, flexible, and responsive molecules and macromolecules as potential support for the controlled particulate assemblies. Molecular surfactants and polyelectrolytes as interfacial agents improve the stability of the nanoparticles whereas swellable and soft shell-like cross-linked polymeric layer at the interface can significantly enhance the uptake of guest nano-constituents during assemblies. Besides, layer-by-layer surface-functionalization holds the ability to provide a high variability in assembly architectures of different interfacial properties. Considering these aspects, various assembly architectures of polymer nanoparticles of tunable size, shapes, morphology, and tailored interfaces together with controllable interfacial interactions are constructed here. The microfluidic-mediated platform has been used for the synthesis of constituents polymer nanoparticles of various structural and interfacial properties, and their assemblies are conducted in batch or flow conditions. The assemblies presented in this progress report is divided into three main categories: cross-linked polymeric network's fusion-based self-assembly, electrostatic-driven assemblies, and assembly formed by encapsulating smaller nanoparticles into larger microparticles.
In situ assembly of gold nanoparticles in the presence of poly-DADMAC resulting in hierarchical and highly fractal nanostructures. - In: Applied Sciences, ISSN 2076-3417, Bd. 11 (2021), 3, 1191, insges. 13 S.
The presence of the polycationic macromolecule poly(diallyldimethylammonium chloride) (poly-DADMAC) has a strong effect on the shape and size of colloidal gold nanoparticles formed by the reduction of tetrachloroauric acid with ascorbic acid in aqueous solution. It slows down nanoparticle growth and supports the formation of nonspherical, partially highly fractal and hierarchical nanoparticle shapes. Four structural levels have been recognized from the near-spherical gold nanoparticles in the lower nanometer range over compact aggregates in the midnanometer range and flower and star-like particles in the submicron range up to larger filamentous aggregates. High-contrast scanning electron microscope (SEM) images show that single gold nanoparticles and clusters of them are connected by bundles of macromolecules in large aggregates. The investigation showed that a large spectrum of different nanoparticle shapes and sizes can be accessed by tuning the poly-DADMAC concentrations and their ratio to other reactants. The nanoassemblies with a very high specific surface area might be of interest for SERS and heterogeneous catalysis.
Sensor micro and nanoparticles for microfluidic application. - In: Applied Sciences, ISSN 2076-3417, Bd. 10 (2020), 23, 8353, insges. 37 S.
Micro and nanoparticles are not only understood as components of materials but as small functional units too. Particles can be designed for the primary transduction of physical and chemical signals and, therefore, become a valuable component in sensing systems. Due to their small size, they are particularly interesting for sensing in microfluidic systems, in microarray arrangements and in miniaturized biotechnological systems and microreactors, in general. Here, an overview of the recent development in the preparation of micro and nanoparticles for sensing purposes in microfluidics and application of particles in various microfluidic devices is presented. The concept of sensor particles is particularly useful for combining a direct contact between cells, biomolecules and media with a contactless optical readout. In addition to the construction and synthesis of micro and nanoparticles with transducer functions, examples of chemical and biological applications are reported.
Emerging structural and interfacial features of particulate polymers at the nanoscale. - In: Langmuir, ISSN 1520-5827, Bd. 36 (2020), 44, S. 13125-13143
Particulate polymers at the nanoscale are exceedingly promising for diversified functional applications ranging from biomedical and energy to sensing, labeling, and catalysis. Tailored structural features (i.e., size, shape, morphology, internal softness, interior cross-linking, etc.) determine polymer nanoparticles' impact on the cargo loading capacity and controlled/sustained release, possibility of endocytosis, degradability, and photostability. The designed interfacial features, however (i.e., stimuli-responsive surfaces, wrinkling, surface porosity, shell-layer swellability, layer-by-layer surface functionalization, surface charge, etc.), regulate nanoparticles interfacial interactions, controlled assembly, movement and collision, and compatibility with the surroundings (e.g., solvent and biological environments). These features define nanoparticles' overall properties/functions on the basis of homogeneity, stability, interfacial tension, and minimization of the surface energy barrier. Lowering of the resultant outcomes is directly influenced by inhomogeneity in the structural and interfacial design through the structure-function relationship. Therefore, a key requirement is to produce well-defined polymer nanoparticles with controlled characteristics. Polymers are amorphous, flexible, and soft, and hence controlling their structural/interfacial features through the single-step process is a challenge. The microfluidics reaction strategy is very promising because of its wide range of advantages such as efficient reactant mixing and fast phase transfer. Overall, this feature article highlights the state-of-the-art synthetic features of polymer nanoparticles with perspectives on their advanced applications.
Microbial community types and signature-like soil bacterial patterns from fortified prehistoric hills of Thuringia (Germany). - In: Community ecology, ISSN 1588-2756, Bd. 21 (2020), 2, S. 107-120
16S rRNA profiling has been applied for the investigation of bacterial communities of surface soil samples from forest-covered areas of ten prehistorical ramparts from different parts of Thuringia. Besides the majority bacterial types that are present in all samples, there could be identified bacteria that are highly abundant in some places and absent or low abundant in others. These differences are mainly related to the acidity of substrate and distinguish the communities of lime stone hills from soils of sand/quartzite and basalt hills. Minority components of bacterial communities show partially large differences that cannot be explained by the pH of the soil or incidental effects, only. They reflect certain relations between the communities of different places and could be regarded as a kind of signature-like patterns. Such relations had also been found in a comparison of the data from ramparts with formerly studied 16S rRNA profiling from an iron-age burial field. The observations are supporting the idea that a part of the components of bacterial communities from soil samples reflect their ecological history and can be understood as the "ecological memory" of a place. Probably such memory effects can date back to prehistoric times and might assist in future interpretations of archaeological findings on the prehistoric use of a place, on the one hand. On the other hand, the genetic profiling of soils of prehistoric places contributes to the evaluation of anthropogenic effects on the development of local soil bacterial diversity.
Novel SERS-based process analysis for label-free segmented flow screenings. - In: Lab on a chip, ISSN 1473-0189, Bd. 20 (2020), 13, S. 2364-2371
Infection-immunity competition: a simple model for illustrating the background of individual response on herd immunity. - In: Applied Sciences, ISSN 2076-3417, Bd. 10 (2020), 9, 3078, insges. 12 S.
Droplet-based screening for the investigation of microbial nonlinear dose-response characteristics system, background, and examples. - In: Micromachines, ISSN 2072-666X, Bd. 11 (2020), 6, 577, insges. 19 S.
Microfluidic chamber design for controlled droplet expansion and coalescence. - In: Micromachines, ISSN 2072-666X, Bd. 11 (2020), 4, 394, insges. 16 S.
Effect of polyalcohols on the anticorrosive behaviour of alkyd coatings prepared with drying oils. - In: Progress in organic coatings, Bd. 145 (2020), 105671
Microfluidically prepared sensor particles for determination of chloride by fluorescence quenching of matrix-embedded lucigenin. - In: SN applied sciences, ISSN 2523-3971, Bd. 2 (2020), 3, 366, insges. 8 S.
Microsegmented flow-assisted miniaturized culturing for isolation and characterization of heavy metal-tolerant bacteria. - In: International journal of environmental science and technology, ISSN 1735-2630, Bd. 17 (2020), 1, S. 1-16
Characterization of Plukenetia volubilis L. fatty acid-based alkyd resins. - In: Polymer testing, ISSN 1873-2348, Bd. 82 (2020), S. 106296
Preparation and deep characterization of composite/hybrid multi-scale and multi-domain polymeric microparticles. - In: Materials, ISSN 1996-1944, Bd. 12 (2019), 23, 3921, insges. 13 S.
Hadesarchaea and other extremophile bacteria from ancient mining areas of the East Harz region (Germany) suggest an ecological long-term memory of soil. - In: SN applied sciences, ISSN 2523-3971, Bd. 1 (2019), 8, 839, insges. 9 S.
Metal nano networks by potential-controlled in situ assembling of gold/silver nanoparticles. - In: ChemistryOpen, ISSN 2191-1363, Bd. 8 (2019), 12, S. 1369-1374
One sensor for multiple colors: fluorescence analysis of microdroplets in microbiological screenings by frequency-division multiplexing. - In: Analytical chemistry, ISSN 1520-6882, Bd. 91 (2019), 4, S. 3055-3061
Complex oscillation modes in the Belousov-Zhabotinsky reaction by weak diffusive coupling. - In: Physical review, ISSN 2470-0053, Bd. 99 (2019), 2, 022202, insges. 6 S.
Boron-doped multi-walled carbon nanotubes as sensing material for analysis of dopamine and epinephrine in presence of uric acid. - In: Chemical physics letters, Bd. 710 (2018), S. 157-167
Single-photon-single-electron transition for interpretation of optical spectra of nonspherical metal nanoparticles in aqueous colloidal solutions. - In: Journal of nanomaterials, ISSN 1687-4129, (2018), Article ID 1781389, insges. 8 S.
The mixed-electrode concept for understanding growth and aggregation behavior of metal nanoparticles in colloidal solution. - In: Applied Sciences, ISSN 2076-3417, Bd. 8 (2018), 8, 1843, insges. 12 S.
The local ecological memory of soil: majority and minority components of bacterial communities in prehistorical urns from Schöps (Germany). - In: International journal of environmental research, ISSN 2008-2304, Bd. 12 (2018), 5, S. 575-584
3D-glass molds for facile production of complex droplet microfluidic chips. - In: Biomicrofluidics, ISSN 1932-1058, Bd. 12 (2018), 2, S. 024115, insges. 9 S.
Single-step in situ assembling routes for the shape control of polymer nanoparticles. - In: Biomacromolecules, ISSN 1526-4602, Bd. 19 (2018), 3, S. 1047-1064
Editorial: Local separation and interface management strategies for biotechnology and life sciences. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 18 (2018), 2, S. 82-83
Surface wrinkling and porosity of polymer particles toward biological and biomedical applications. - In: Advanced materials interfaces, ISSN 2196-7350, Bd. 4 (2017), 24, 1700929, S. 1-15
Interfacial-active polymer nanoparticles, their assemblies, and SERS application. - In: Macromolecular chemistry and physics, ISSN 1521-3935, Bd. 218 (2017), 23, S. 1700261, insges. 10 S.
Mikrofluidik - großes Potenzial in kleinen Tropfen. - In: Biospektrum, ISSN 1868-6249, Bd. 23 (2017), 4, S. 394-397
Hierarchically structured particles for micro flow catalysis. - In: The chemical engineering journal, ISSN 1873-3212, Bd. 326 (2017), S. 1058-1065
Stochastically reduced communities - microfluidic compartments as model and investigation tool for soil microorganism growth in structured spaces. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 17 (2017), 7, S. 792-800
Optimising sodium silica gel for Ferroin immobilization. - In: Journal of porous materials, ISSN 1573-4854, Bd. 24 (2017), 4, S. 923-932
Combination of microfluidic high-throughput production and parameter screening for efficient shaping of gold nanocubes using Dean-flow mixing. - In: Lab on a chip, ISSN 1473-0189, Bd. 17 (2017), 8, S. 1487-1495
Application of polyionic macromolecules in micro flow syntheses of nanoparticles. - In: Macromolecular chemistry and physics, ISSN 1521-3935, Bd. 218 (2017), 2, S. 1600371, insges. 13 S.
Electrochemical response of nitrogen-doped multi-walled carbon nanotubes decorated with gold and iridium nanoparticles toward ferrocyanide/ferricyanide redox system. - In: Ionics, ISSN 1862-0760, Bd. 22 (2016), 10, S. 1957-1965
Microflow-assisted assembling of multi-scale polymer particles by controlling surface properties and interactions. - In: European polymer journal, Bd. 80 (2016), S. 256-267
Explanation of the size dependent in-plane optical resonance of triangular silver nanoprisms. - In: Physical chemistry, chemical physics, ISSN 1463-9084, Bd. 18 (2016), 23, S. 15943-15949
High precision attachment of silver nanoparticles on AFM tips by dielectrophoresis. - In: Analytical and bioanalytical chemistry, ISSN 1618-2650, Bd. 408 (2016), 13, S. 3625-3631
Micro-flow assisted synthesis of fluorescent polymer nanoparticles with tuned size and surface properties. - In: Nanotechnology reviews, ISSN 2191-9097, Bd. 5 (2016), 2, S. 259-272
Electrochemical analysis of ascorbic acid, dopamine, and uric acid on nobel metal modified nitrogen-doped carbon nanotubes. - In: Sensors and actuators, ISSN 0925-4005, Bd. 231 (2016), S. 218-229
Gold nanocubes - direct comparison of synthesis approaches reveals the need for a microfluidic synthesis setup for a high reproducibility. - In: The chemical engineering journal, ISSN 1873-3212, Bd. 288 (2016), S. 432-440
Process control in microreactors. - In: Chemical engineering & technology, ISSN 1521-4125, Bd. 38 (2015), 7, S. 1107-1108
Microfluidic assisted synthesis of multipurpose polymer nanoassembly particles for fluorescence, LSPR, and SERS activities. - In: Small, ISSN 1613-6829, Bd. 11 (2015), 48, S. 6435-6443
Changing growth behavior of heavy-metal tolerant bacteria: media optimization using droplet-based microfluidics. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 15 (2015), 3, S. 327-332
Identification of response classes from heavy metal-tolerant soil microbial communities by highly resolved concentration-dependent screenings in a microfluidic system. - In: Methods in ecology and evolution, ISSN 2041-210X, Bd. 6 (2015), 5, S. 600-609
Composite sensor particles for tuned SERS sensing: microfluidic synthesis, properties and applications. - In: ACS applied materials & interfaces, ISSN 1944-8252, Bd. 7 (2015), 20, S. 10742-10754
Role of self-polarization in a single-step controlled synthesis of linear and branched polymer nanoparticles. - In: Macromolecular chemistry and physics, ISSN 1521-3935, Bd. 216 (2015), 11, S. 1212-1219
What are proteins teaching us on fundamental strategies for molecular nanotechnology?. - In: Nanotechnology reviews, ISSN 2191-9097, Bd. 4 (2015), 2, S. 145-160
Small gold nanoparticles formed by rapid photochemical flow-through synthesis using microfluid segment technique. - In: Journal of nanoparticle research, ISSN 1572-896X, Bd. 17.2015, 2, Article 99, insges. 8 S.
Oxygen sensor nanoparticles for monitoring bacterial growth and characterization of dose-response functions in microfluidic screenings. - In: Microchimica acta, ISSN 1436-5073, Bd. 182 (2015), 1/2, S. 385-394
Simultaneous size and color tuning of polymer microparticles in a single-step microfluidic synthesis: particles for fluorescence labeling. - In: Journal of materials chemistry. Materials for optical and electronic devices / Royal Society of Chemistry. - London [u.a.] : RSC, 2013- , ISSN: 2050-7534 , ZDB-ID: 2702245-6, ISSN 2050-7534, Bd. 3 (2015), 4, S. 844-853
Initiation of atrial fibrillation by interaction of pacemakers with geometrical constraints. - In: Journal of theoretical biology, ISSN 1095-8541, Bd. 366 (2015), S. 13-23
Droplet-based microfluidics for microtoxicological studies. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 15 (2015), 3, S. 306-317
Controlling formation and assembling of nanoparticles by control of electrical charging, polarization, and electrochemical potential. - In: Nanotechnology reviews, ISSN 2191-9097, Bd. 3 (2014), 6, S. 553-568
Nitrogen-doped multi-walled carbon nanotubes modified with platinum, palladium, rhodium and silver nanoparticles in electrochemical sensing. - In: Journal of nanoparticle research, ISSN 1572-896X, Bd. 16.2014, 10, Article 2660, insges. 13 S.
Micro-segmented flow and multisensor-technology for microbial activity profiling. - In: Environmental science, ISSN 2050-7895, Bd. 16 (2014), 10, S. 2362-2370
Control of shape and size of polymer nanoparticles aggregates in a single-step microcontinuous flow process: a case of flower and spherical shapes. - In: Langmuir, ISSN 1520-5827, Bd. 30 (2014), 41, S. 12180-12189
Multi-walled carbon nanotubes modified with gold nanoparticles with various diameters for the simultaneous analysis of dopamine and uric acid in a single experiment. - In: Sensor letters, ISSN 1546-1971, Bd. 12 (2014), 1, S. 153-159
Continuous-microflow synthesis and morphological characterization of multiscale composite materials based on polymer microparticles and inorganic nanoparticles. - In: Journal of flow chemistry, ISSN 2063-0212, Bd. 4 (2014), 2, S. 72-78
Single-step microfluidic synthesis of various nonspherical polymer nanoparticles via in situ assembling: dominating role of polyelectrolytes molecules. - In: ACS applied materials & interfaces, ISSN 1944-8252, Bd. 6 (2014), 14, S. 11254-11264
ChemInform abstract: Direct access to 3-substituted 1,4-oxathiepino[5,6-b]pyridine-5-one through one-pot substitution cyclization reaction of 2-mercapto-3-nicotinic acid with [alpha]-bromo ketones. - In: ChemInform, ISSN 1522-2667, Bd. 45 (2014), 25, insges. 1 S.
The ecological time-scale violation by industrial society and the chemical challenges for transition to a sustainable global entropy export management. - In: Green processing & synthesis, ISSN 2191-9550, Bd. 3 (2014), 1, S. 33-45
Screening of nanoparticle properties in microfluidic syntheses. - In: Nanotechnology reviews, ISSN 2191-9097, Bd. 3 (2014), 1, S. 5-26
Nanometer precise adjustment of the silver shell thickness during automated Au-Ag core-shell nanoparticle synthesis in micro fluid segment sequences. - In: Nanoscale, ISSN 2040-3372, Bd. 6 (2014), 10, S. 5230-5238
Electrocatalytic activity of nitrogen-doped carbon nanotubes decorated with gold nanoparticles. - In: Electrocatalysis, ISSN 1868-5994, Bd. 5 (2014), 1, S. 87-95
Direct access to 3-substituted 1,4-oxathiepino[5,6-b]pyridine-5-one through one-pot substitution cyclization reaction of 2-mercapto-3-nicotinic acid with [alpha]-bromo ketones. - In: Tetrahedron letters, ISSN 1873-3581, Bd. 55 (2014), 2, S. 358-361
Characterization of combinatorial effects of toxic substances by cell cultivation in micro segmented flow. - In: Micro-segmented flow, (2014), S. 203-230
Micro continuous-flow synthesis of metal nanoparticles using micro fluid segment technology. - In: Micro-segmented flow, (2014), S. 149-200
Electrical switching of droplets and fluid segments. - In: Micro-segmented flow, (2014), S. 31-54
Thermodynamic investigation of ferrocyanide/ferricyanide redox system on nitrogen-doped multi-walled carbon nanotubes decorated with gold nanoparticles. - In: Thermochimica acta, Bd. 576 (2014), S. 1-8
Engineering polymer microparticles by droplet microfluidics. - In: Journal of flow chemistry, ISSN 2063-0212, Bd. 3 (2013), 3, S. 66-75
Investigation of mixture toxicity of widely used drugs caffeine and ampicillin in the presence of an ACE inhibitor on bacterial growth using droplet-based microfluidic technique. - In: Green processing & synthesis, ISSN 2191-9550, Bd. 2 (2013), 6, S. 591-601
A self-seeding synthesis of Ag microrods of tuned aspect ratio: ascorbic acid plays a key role. - In: Nanotechnology, ISSN 1361-6528, Bd. 24 (2013), 34, 345604, S. 1-11
Application of micro-segmented flow for two-dimensional characterization of the combinatorial effect of zinc and copper ions on metal-tolerant Streptomyces strains. - In: Applied microbiology and biotechnology, ISSN 1432-0614, Bd. 97 (2013), 20, S. 8923-8930
Geometric optimization of liquid-liquid slug flow in a flow-focusing millifluidic device for synthesis of nanomaterials. - In: The chemical engineering journal, ISSN 1873-3212, Bd. 217 (2013), S. 447-459
Biotechnology and microsystems: give and take between enzymatic synthesis, cell cultivation and microstructuring. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 13 (2013), 4, S. 323-324
Robotic alliance of miniaturized synthesis and screening: a case study for the identification of histone deacetylase inhibitors. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 13 (2013), 4, S. 344-351
Heterogeneous nanoassembling: microfluidically prepared poly(methyl methacrylate) nanoparticles on Ag microrods and ZnO microflowers. - In: Particle & particle systems characterization, ISSN 1521-4117, Bd. 30 (2013), 7, S. 614-623
Irregular excitation patterns in reaction-diffusion systems due to perturbation by secondary pacemakers. - In: Physical review. Statistical, nonlinear, and soft matter physics / American Physical Society. - College Park, Md. : APS, January 1993-December 2015 , ISSN: 1550-2376 , ZDB-ID: 1472725-0, ISSN 1550-2376, Bd. 87 (2013), 4, S. 042904, insges. 8 S.
Why is micro segmented flow particularly promising for the synthesis of nanomaterials?. - In: Chemical engineering & technology, ISSN 1521-4125, Bd. 36 (2013), 6, S. 887-899
Screening of multiparameter spaces for silver nanoprism synthesis by microsegmented flow technique. - In: Chemie - Ingenieur - Technik, ISSN 1522-2640, Bd. 85 (2013), 4, S. 467-475
Microfluidic encoding: generation of arbitrary droplet sequences by electrical switching in microchannels. - In: Sensors and actuators, ISSN 1873-3069, Bd. 189 (2013), S. 288-297
Continuous-flow preparation of nanoporous metal/polymer composite particles by in situ synthesis of silver nanoparticles in photopolymerized acrylate/diethylene glycol droplets. - In: Journal of materials science, ISSN 1573-4803, Bd. 48 (2013), 5, S. 2158-2166
Spontaneous transformation of polyelectrolyte-stabilized silver nanoprisms by interaction with thiocyanate. - In: Journal of colloid and interface science, ISSN 1095-7103, Bd. 394 (2013), S. 78-84
Polyacrylamid/silver composite particles produced via microfluidic photopolymerization for single particle-based SERS microsensorics. - In: Analytical chemistry, ISSN 1520-6882, Bd. 85 (2013), 1, S. 313-318
Synthesis and characterization of ZnO/4-mercaptobenzoic acid/Au composite particles. - In: Materials letters, ISSN 1873-4979, Bd. 91 (2013), S. 103-106
Addressing of concentration spaces for bioscreenings by micro segmented flow with microphotometric and microfluorimetric detection, (2012), S. 47-81
Stimulation and inhibition of bacterial growth by caffeine dependent on chloramphenicol and a phenolic uncoupler - a ternary toxicity study using microfluid segment technique. - In: Journal of biomedical nanotechnology, ISSN 1550-7041, Bd. 8 (2012), 5, S. 770-778
Microsegmented flow-through synthesis of silver nanoprisms with exact tunable optical properties. - In: The journal of physical chemistry. C, Nanomaterials and interfaces / American Chemical Society. - Washington, DC : Soc., 2007- , ISSN: 1932-7455 , ZDB-ID: 2256522-X, ISSN 1932-7455, Bd. 116 (2012), 16, S. 9251-9258
Local structure of ZnO micro flowers and nanoparticles obtained by micro-segmented flow synthesis. - In: ChemPhysChem, ISSN 1439-7641, Bd. 13 (2012), 6, S. 1557-1561
Uncovering toxicological complexity by multi-dimensional screenings in microsegmented flow: modulation of antibiotic interference by nanoparticles. - In: Lab on a chip, ISSN 1473-0189, Bd. 12 (2012), 3, S. 474-484
ChemInform abstract: Convenient method for synthesis of thiazolo[3,2-a]pyrimidine derivatives in a one-pot procedure. - In: ChemInform, ISSN 1522-2667, Bd. 42 (2011), 44, insges. 1 S.
ChemInform abstract: Gold-nanoparticle-catalyzed synthesis of propargylamines: the traditional A 3 -multicomponent reaction performed as a two-step flow process. - In: ChemInform, ISSN 1522-2667, Bd. 42 (2011), 27, insges. 1 S.
From droplets and particles to hierarchical spatial organization: nanotechnology challenges for microfluidics. - In: Journal of physical science and application, ISSN 2159-5348, Bd. 1 (2011), 3, S. 125-134
The compartimentation of fluids in the microliter, nanoliter and picoliter range leads recently to many applications of microfluidics in material development, diagnostics and biological screenings. Droplet-based microfluidics allows the improvement of nanoparticle homogeneity and the tuning of particle properties. It supports combinatorial synthesis of inorganic as well as organic substances and can be applied for the cultivation and screening of bacteria, eucaryotic cells and fish embryos. The well-ordered handling and the addressing of microfluid segments improves the information transfer between chemical, biological and electronic systems. Despite this remarkable technical progress, there is a particular importance of microfluidics for future nanotechnological solutions. The hierarchical spatial organization of liquids, particles and gels in microfluidics represents a fundamental biomimetic principle which overcomes the limits of planar technology and opens the gate for realizing complex structured threedimensional nanoarchitectures. Recent applications of microstructured fluids in chemistry and biology and concepts for future developments will be discussed.
The Eschenmoser coupling reaction under continuous-flow conditions. - In: Beilstein journal of organic chemistry, ISSN 1860-5397, Bd. 7 (2011), S. 1164-1172
Gold nanoparticle-catalyzed synthesis of propargylamines: the traditional A3-multicomponent reaction performed as a two-step flow process. - In: Chemistry - a European journal, ISSN 1521-3765, Bd. 17 (2011), 10, S. 3005-3010
Residence time distribution studies in microfluidic mixing structures. - In: Chemical engineering & technology, ISSN 1521-4125, Bd. 34 (2011), 3, S. 361-370
The residence time distribution (RTD) characteristics of three microreactors containing different passive mixing structures, namely, a three dimensional serpentine structure, a split-and-recombine structure and a staggered herringbone structure, were investigated and compared. An experimental input-response technique was applied which required deconvolution of the measured data by modeling of the RTD. The proposed technique provides useful information on optimized application and operation of microfluidic devices. The serpentine reactor and the split-and-recombine reactor show improvement in RTD behaviour, i.e., narrowing of RTD curves, at Re-numbers > 30 due to effective transversal mixing and therefore reduced axial dispersion. In the case of the staggered herringbone structure, dead volumes could be observed which considerably affect the RTD.
Microtechnology in chemical engineering. - In: Chemical engineering & technology, ISSN 1521-4125, Bd. 34 (2011), 3, S. 330
Cultivation of Chlorella vulgaris in microfluid segments and microtoxicological determination of their sensitivity against CuCl2 in the nanoliter range. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 11 (2011), 6, S. 580-587
The cultivation of the monocellular green alga Chlorella vulgaris was implemented into microfluid segments to demonstrate the possibility of an automated screening of toxic effects of the common algaecide CuCl2. Therefore, the nutritional as well as light and carbon dioxide requirements of the algae had to be adapted to the microfluidic device. Generally, sequences of about 350 fluid segments with single volumes of about 500 nL were applied for the dose-response experiments. The growth of algae cultures inside microfluidic segments was noninvasively measured by microflow through techniques using two different optical channels. A multi-endpoint detection was realized by the photometric characterization of cell density by transmission measurements and the measurement of density of autofluorescent cells. The different methods revealed comparable half maximal effective concentrations (EC50) in the range between 34.6 and 39.9 mg/mL for the toxicity of CuCl2 to the green algae C. vulgaris. By reference experiments in microtiter plates lower EC50 were achieved presumably caused by increased alkalinity of the growth medium due to higher photosynthesis. The results show that the microsegmented flow technique is well suited for the automated determination of dose/response functions for microorganisms like C. vulgaris and for the application of multi-endpoint procedures at the nanoliter scale.
Editorial: microtechnology for life science applications. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 11 (2011), 2, S. 116-117
Synergistic effects of metal nanoparticles and a phenolic uncoupler using microdroplet-based two-dimensional approach. - In: Journal of environmental monitoring, ISSN 1464-0333, Bd. 2 (2011), 13, S. 410-415
A droplet-based microfluidic technique for testing multiple reagent concentrations is presented. We used this experimental approach to study combined effects of gold (AuNP) and silver nanoparticles (AgNP) with the phenolic uncoupler 2,4-dinitrophenol (DNP) with respect to the growth of Escherichia coli. In order to evaluate the toxicity of binary mixtures, we first encapsulated the E. coli cells and particle mixtures inside the microdroplets using PEEK (polyetherketone) modules. Two-dimensional concentration spaces with about 500 well separated droplets were addressed. We subsequently analyzed the cell growth, the viability and the autofluorescence intensity (metabolic activity) of the bacteria with a micro-flow-through fluorometer and photometer. Dose-dependent synergistic effects were found for the binary mixture of AgNPs and DNP, which indicated a stronger interaction in the mixture than it was expected from effect summation. For the binary mixture of DNP and AuNPs in non-toxic concentrations, we found only weak synergistic effects at low DNP concentrations. Furthermore, the non-toxic tested AuNPs causes effect summation in the binary mixture with the phenolic uncoupler. In general, we demonstrated the efficiency of a droplet-based microfluidic system for fast high-throughput screenings of binary and multiple mixtures. This work also confirmed the relevance of highly resolved droplet-based assays for the miniaturization of ecotoxicological aquatic test systems.
Convenient method for synthesis of thiazolo[3,2-a]pyrimidine derivatives in a one-pot procedure. - In: Tetrahedron letters, ISSN 1873-3581, Bd. 52 (2011), 29, S. 3814-3817
Au/Ag/Au double shell nanoparticles with narrow size distribution obtained by continuous micro segmented flow synthesis. - In: The chemical engineering journal, ISSN 1873-3212, Bd. 166 (2011), 3, S. 1164-1169
Metal nanoparticle synthesis in microreactors. - In: Applications, (2010), S. 361-393
Residence time distribution and nanoparticle formation in microreactors. - In: Fundamental concepts, (2010), S. 317-340
Ethyl 2-[(Z)-2-(4-cyanophenyl)-2-hydroxyvinyl]-4-(4-methoxyphenyl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate. - In: Molbank, ISSN 1422-8599, (2010), 1, M655, insges. 3 S.
Pressure loss - educational experiments for microreaction technology using an universal experiment platform. - In: Chemie - Ingenieur - Technik, ISSN 1522-2640, Bd. 82 (2010), 10, S. 1789-1798
Effect of water content on growth and optical properties of ZnO nanoparticles generated in binary solvent mixtures by micro-continuous flow synthesis. - In: The chemical engineering journal, ISSN 1873-3212, Bd. 165 (2010), 3, S. 958-965
Multiscale materials from microcontinuous-flow synthesis: ZnO and Au nanoparticle-filled uniform and homogeneous polymer microbeads. - In: Nanotechnology, ISSN 1361-6528, Bd. 21 (2010), 1, 015605, S. 1-5
ChemInform abstract: Facile conversion of Biginelli 3,4-dihydropyrimidin-2(1H)-thiones to 2-(2-hydroxy-2-arylvinyl) dihydropyrimidines via Eschenmoser coupling. - In: ChemInform, ISSN 1522-2667, Bd. 40 (2009), 31, insges. 1 S.
Heterogeneous catalyzed pyridine synthesis using montmorillionite and nanoparticle-impregnated alumina in a continuous micro flow system. - In: Chemical engineering & technology, ISSN 1521-4125, Bd. 32 (2009), 11, S. 1799-1805
Micro segmented-flow technique for continuous synthesis of different kinds of ZnO nanoparticles in aqueous and in DMSO solution. - In: Journal of chemical engineering of Japan, ISSN 0021-9592, Bd. 42 (2009), 5, S. 338-345
Highly resolved doseresponse functions for drug-modulated bacteria cultivation obtained by fluorometric and photometric flow-through sensing in microsegmented flow. - In: Sensors and actuators. Chemical. - Amsterdam [u.a.] : Elsevier Science, 1990- , ISSN: 0925-4005 , ZDB-ID: 1500731-5, ISSN 0925-4005, Bd. 142 (2009), 1, S. 66-72
A hydrogel based fluorescent micro array used for the characterization of liquid analytes. - In: Analytica chimica acta, ISSN 1873-4324, Bd. 633 (2009), 1, S. 81-89
Gold and gold-silver core-shell nanoparticle constructs with defined size based on DNA hybridization. - In: Journal of nanoparticle research, ISSN 1572-896X, Bd. 11 (2009), 3, S. 623-633
Nanotopographic characterization of spotted micro arrays on polyvinyl alcohol films by high-resolution long-range nanoprofiling. - In: Scanning, ISSN 1932-8745, Bd. 31 (2009), 1, S. 35-48
Monitoring cell cultivation in microfluidic segments by optical pH sensing with a micro flow-through fluorometer using dye-doped polymer particles. - In: Microchimica acta, ISSN 1436-5073, Bd. 164 (2009), 3/4, S. 279-286
Application of an asymmetric helical tube reactor for fast identification of gene transcripts of pathogenic viruses by micro flow-through PCR. - In: Biomedical microdevices, ISSN 1572-8781, Bd. 11 (2009), 3, S. 685-692
Photoluminescence effects on gold nano-particles modified by short single stranded DNA molecules. - In: Materials science and engineering technology, ISSN 1521-4052, Bd. 40 (2009), 4, S. 290-293
Facile conversion of Biginelli 3,4-dihydropyrimidin-2(1H)-thiones to 2-(2-hydroxy-2-arylvinyl) dihydropyrimidines via Eschenmoser coupling. - In: Tetrahedron letters, ISSN 1873-3581, Bd. 50 (2009), 16, S. 1838-1843
Inorganic particles. - In: Devices, reactions and applications, (2009), S. 273-288
Differentiation of liquid analytes in gel films by permeability-modulated double-layer chemo-chips/ Aniket R. Thete; G. Alexander Gross and J. Michael Koehler. - In: The analyst, ISSN 1364-5528, Bd. 134 (2009), 2, S. 394-400
A hydrogel based fluorescent micro array used for the characterization of liquid analytes. - In: Analytica chimica acta, ISSN 1873-4324, Bd. 633 (2009), 1, S. 81-89
Isotropic etching. - In: Encyclopedia of microfluidics and nanofluidics, (2008), S. 877-884
PCR Lab-on-Chip devices. - In: Encyclopedia of microfluidics and nanofluidics, (2008), S. 1618-1626
Microsegmented flow. - In: Encyclopedia of microfluidics and nanofluidics, (2008), S. 1335-1342
Optically controlled thermal management on the nanometer length scale. - In: Nanotechnology, ISSN 1361-6528, Bd. 19 (2008), 5, 055207, S. 1-12
Fabrication and fluidic characterization of static micromixers made of low temperature cofired ceramic (LTCC). - In: Chemical engineering science, Bd. 63 (2008), 10, S. 2773-2784
Preparation of metal nanoparticles with varied composition for catalytical applications in microreactors. - In: Chemical engineering science, Bd. 63 (2008), 20, S. 5048-5055
Nano-calorimetry of small-sized biological samples. - In: Thermochimica acta, Bd. 477 (2008), 1/2, S. 48-53
Viscosity-dependent enhancement of fluid resistance in water/glycerol micro fluid segments. - In: Microfluidics and nanofluidics, ISSN 1613-4990, Bd. 5 (2008), 2, S. 281-287
Technical concept of a flow-through microreactor for in-situ RT-PCR. - In: Engineering in life sciences, ISSN 1618-2863, Bd. 8 (2008), 1, S. 68-72
A reproducible surface-enhanced raman spectroscopy approach : online SERS measurements in a segmented microfluidic system. - In: Analytical chemistry, ISSN 1520-6882, Bd. 79 (2007), 4, S. 1542-1547
Phylogenetic analysis of the Brachyura (Crustacea, Decapoda) based on characters of the foregut with establishment of a new taxon. - In: Journal of zoological systematics and evolutionary research, ISSN 1439-0469, Bd. 45 (2007), 1, S. 20-32
Micro fluid segment technique for screening and development studies on Danio rerio embryos. - In: Lab on a chip, ISSN 1473-0189, Bd. 7 (2007), 9, S. 1132-1138
Microphotometric characterization of fluid segment populations generated in different simple microfluidic networks. - In: Microfluidics and nanofluidics, ISSN 1613-4990, Bd. 3 (2007), 6, S. 653-663
Formation and fluorimetric characterization of micelles in a micro-flow through system with static micro mixer. - In: Sensors, ISSN 1424-8220, Bd. 7 (2007), 11, S. 2499-2509
Formation of star-like and core-shell AuAg nanoparticles during two- and three-step preparation in batch and in microfluidic systems. - In: Journal of nanomaterials, ISSN 1687-4129, (2007), Article ID 98134, insges. 7 S.
Spatially encoded single-bead Biginelli synthesis in a microstructured silicon array. - In: Angewandte Chemie, ISSN 1521-3757, Bd. 118 (2006), 19, S. 3174-3178
Microreactor array assembly, designed for diversity oriented synthesis using a multiple core structure library on solid support. - In: QSAR & combinatorial science, ISSN 1611-0218, Bd. 25 (2006), 11, S. 1055-1062
"Syn&Sort": a chip-based tool for combinatorial synthesis. - In: QSAR & combinatorial science, ISSN 1611-0218, Bd. 25 (2006), 11, S. 1063-1068
Erratum. - Bd. 26.2007, 4, S. 581
Laboratory applications of microstructured devices in student education. - In: Micro process engineering, (2006), S. 463-495
Bildung von Goldnanopartikeln und Nanopartikelaggregaten in statischen Mikromischern in Gegenwart von Rinderserumalbumin (BSA). - In: Chemie - Ingenieur - Technik, ISSN 1522-2640, Bd. 77 (2005), 7, S. 867-873
Novel trigonal prismatic iron complexes of expanded hexadentate Jäger type ligands: synthesis and X-ray analysis. - In: Inorganica chimica acta, ISSN 0020-1693, Bd. 358 (2005), 3, S. 808-813
Chip devices for miniaturized biotechnology. - In: Applied microbiology and biotechnology, ISSN 1432-0614, Bd. 69 (2005), 2, S. 113-125
Formation of isolated and clustered Au nanoparticles in the presence of polyelectrolyte molecules using a flow-through Si chip reactor. - In: Journal of materials chemistry, ISSN 1364-5501, Bd. 15 (2005), 19, S. 1924-1930
Continuous synthesis of gold nanoparticles in a microreactor. - In: Nano letters, ISSN 1530-6992, Bd. 5 (2005), 4, S. 685-691
Formation of monomeric and novolak azo dyes in nanofluid segments by use of a double injector chip reactor. - In: Chemical engineering & technology, ISSN 1521-4125, Bd. 28 (2005), 4, S. 520-527
Nanoliter segment formation in micro fluid devices for chemical and biological micro serial flow processes in dependence on flow rate and viscosity. - In: Sensors and actuators. Physical: an international journal devoted to research and development of physical transducers. - Amsterdam [u.a.] : Elsevier Science, 1990- , ISSN: 1873-3069 , ZDB-ID: 1500729-7, ISSN 1873-3069, Bd. 119 (2005), 1, S. 19-27
Chipreaktoren im Labor - ein Beitrag zur nachhaltigen Umweltvorsorge. - In: Chemie - Ingenieur - Technik, ISSN 1522-2640, Bd. 76 (2004), 5, S. 605-606
Elektrochemische Mikrodurchflussanordnung für Standardexperimente im Studium. - In: Chemie - Ingenieur - Technik, ISSN 1522-2640, Bd. 19 (2004), 5, S. 522-526
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