Refine
Year of publication
Document Type
- Article (540)
- Conference Proceeding (52)
- Part of a Book (9)
- Doctoral Thesis (4)
- Book (3)
- Other (2)
- Report (2)
- Patent (1)
Language
- English (555)
- German (57)
- Multiple languages (1)
Keywords
- Biosensor (6)
- Graduiertentagung (4)
- biosensors (4)
- frequency mixing magnetic detection (4)
- LAPS (3)
- Label-free detection (3)
- Light-addressable potentiometric sensor (3)
- capacitive field-effect sensor (3)
- field-effect sensor (3)
- hydrogen peroxide (3)
- magnetic nanoparticles (3)
- tobacco mosaic virus (TMV) (3)
- Acyl-amino acids (2)
- Aminoacylase (2)
- Bacillaceae (2)
- Bacillus atrophaeus (2)
- Biotechnological application (2)
- Calorimetric gas sensor (2)
- Capacitive field-effect sensor (2)
- Hydrogen peroxide (2)
- Raman spectroscopy (2)
- Subtilases (2)
- Subtilisin (2)
- Tobacco mosaic virus (TMV) (2)
- acetoin (2)
- capacitive field-effect sensors (2)
- gold nanoparticles (2)
- light-addressable potentiometric sensor (2)
- penicillinase (2)
- sterilisation (2)
- (Bio)degradation (1)
- Aachen / Fachhochschule Aachen (1)
- Acylation (1)
- Alginate beads (1)
- Alkalihalobacillus okhensis (1)
- Bacillus atrophaeus spores (1)
- Bio-Sensors (1)
- Bioabsorbable (1)
- Biocatalysis (1)
- Biosensorik (1)
- Biosurfactants (1)
- Broad pH spectrum (1)
- CNOT (1)
- CRISPR/Cas9 (1)
- Capacitive field-effect (1)
- Capacitive model (1)
- Chaperone (1)
- Chaperone co-expression (1)
- Chemical images (1)
- Chemical imaging (1)
- Chemical imaging sensor (1)
- Chemical sensor (1)
- Choleratoxin B (1)
- Coat protein (1)
- C–V method (1)
- DNA biosensor (1)
- DPA (dipicolinic acid) (1)
- Dehydrogenase (1)
- Detergent protease (1)
- Diaphorase (1)
- EIS capacitive sensor (1)
- Electrolyte–insulator–semiconductor (1)
- Enzymatic biosensor (1)
- Enzyme coverage (1)
- Enzyme logic gate (1)
- Enzyme nanocarrier (1)
- Extracellular enzymes (1)
- Field effect (1)
- Field-effect biosensor (1)
- Field-effect device (1)
- Field-effect sensor (1)
- GaAs hot electron injector (1)
- Gas sensor (1)
- Glucose biosensor (1)
- Glucose oxidase (1)
- Gold nanoparticles (1)
- Graduate symposium (1)
- Graduierter (1)
- Gunn diode (1)
- Halotolerant protease (1)
- Heavy metal detection (1)
- Hypersecretion (1)
- ISFET (1)
- Impedance spectroscopy (1)
- Inclusion bodies (1)
- Lab-on-Chip (1)
- Layer-by-layer adsorption (1)
- LbL films (1)
- MOS (1)
- Marker-free mutagenesis (1)
- Multi-sensor system (1)
- Multianalyte detection (1)
- Multicell (1)
- Multiplexing (1)
- Nano Materials (1)
- Nanomaterial (1)
- Nanostructuring (1)
- Nanotechnologie (1)
- Negative impedance convertor (1)
- O2 plasma (1)
- Organic light-emitting diode display (1)
- Penicillin (1)
- Plant virus (1)
- Poly(allylamine hydrochloride) (1)
- Poly(d,l-lacticacid) (1)
- Polyimide (1)
- Polylactide acid (1)
- Potentiometry (1)
- Promotionsstudium (1)
- Real-time monitoring (1)
- Resistive temperature detector (1)
- Resonance-mode measurement (1)
- Silk fibroin (1)
- Simultaneous determination (1)
- Sn₃O₄ (1)
- Stenotrophomonas maltophilia (1)
- Sterilisation process (1)
- Streptomyces griseus (1)
- Streptomyces lividans (1)
- TMV adsorption (1)
- Ta₂O₅ gate (1)
- Tobacco mosaic virus (1)
- Trinkwassersicherheit (1)
- Uracil-phosphoribosyltransferase (1)
- Vibrio natriegens (1)
- Wafer (1)
- XOR (1)
- Zeta potential (1)
- acetoin reductase (1)
- actuator-sensor system (1)
- alcoholic beverages (1)
- aminooctanethiol (1)
- amperometric biosensors (1)
- annealing (1)
- artificial olfactory image (1)
- aseptic parameters (1)
- aspergillus (1)
- atomic layer deposition (1)
- bi-enzyme biosensor (1)
- bioburdens (1)
- biocompatible (1)
- biocompatible materials (1)
- biodegradabl (1)
- biodegradable electronic devices (1)
- biosensor (1)
- calorimetric gas sensor (1)
- calorimetric gas sensor;hydrogen peroxide;wireless sensor system (1)
- capacitive EIS sensor (1)
- capacitive electrolyte–insulator–semiconductor sensors (1)
- capacitive field-effect biosensor (1)
- capacitive model (1)
- capillary micro-droplet cell (1)
- carbon electrodes (1)
- catalytic decomposition (1)
- catalytic metal (1)
- chemical sensor (1)
- cholera toxin B (1)
- colorization (1)
- control gate (1)
- coupled Néel–Brownian relaxation dynamics (1)
- detection of charged macromolecules (1)
- detergent protease (1)
- drinking water safety (1)
- electrolyte-insulator semiconductor sensor (EIS) (1)
- electrolyte-insulator-semiconductor capacitors (1)
- electronic nose (1)
- encapsulation materials (1)
- endospores (1)
- enzymatic biosensor (1)
- enzyme cascade (1)
- enzyme immobilization (1)
- enzyme kinetics (1)
- enzyme-logic gate (1)
- equivalent circuit (1)
- fibroin (1)
- field-effect structure (1)
- filamentous fungi (1)
- frequency mixing (1)
- gas sensor (1)
- gaseous hydrogen peroxide (1)
- genome engineering (1)
- glucose (1)
- glucose oxidase (GOx) (1)
- graphene oxide (1)
- halotolerant protease (1)
- heavy metals (1)
- high-alkaline subtilisin (1)
- horseradish peroxidase (HRP) (1)
- hydroxylation (1)
- immobilization (1)
- key performance indicators (1)
- layer expansion (1)
- layer-by-layer technique (1)
- light-addressable electrode (1)
- light-addressing technologies (1)
- magnetic actuation (1)
- magnetic beads (1)
- magnetic biosensing (1)
- magnetic frequency mixing technique (1)
- magnetic relaxation (1)
- magnetic sandwich immunoassay (1)
- magnetic sensing (1)
- magnetic sensors (1)
- magnetic separation (1)
- magnetic tweezers (1)
- magnetophoretic velocity (1)
- metal-oxide-semiconductor structure (1)
- microfluidics (1)
- micromagnetic simulation (1)
- microwave generation (1)
- multi-sensing platform (1)
- multianalyte detection (1)
- multiparametric immunoassays (1)
- multiplex detection (1)
- nanobelts (1)
- nanomaterials (1)
- nanoparticle coverage (1)
- on-chip integrated addressable EISCAP sensors (1)
- optical sensor setup (1)
- optical spore trapping (1)
- optical trapping (1)
- organic PVC membranes (1)
- organosilanes (1)
- oxidative stable protease (1)
- pH sensors (1)
- pattern-size reduction (1)
- penicillin (1)
- photoelectrochemistry (1)
- plant virus detection (1)
- plug-based microfluidic device (1)
- polyaniline (1)
- polystyrene sulfonate (1)
- recombinant expression (1)
- scanned light pulse technique (1)
- self-aligned patterning (1)
- silanization (1)
- spore kill rate (1)
- sterility (1)
- sterility tests (1)
- sterilization (1)
- sterilization conditions (1)
- sterilization efficacy (1)
- sterilization methods (1)
- superparamagnetic bead (1)
- superparamagnetic nanoparticles (1)
- surface functionalization (1)
- temperature (1)
- thin-film microsensors (1)
- titanium dioxide photoanode (1)
- turnip vein clearing virus (TVCV) (1)
- ultrathin gate insulators (1)
- urease (1)
- validation methods (1)
- visualization (1)
- wafer-level testing (1)
- α-aminoacylase (1)
- ε-lysine acylase (1)
Institute
- INB - Institut für Nano- und Biotechnologien (613) (remove)
Monitoring the cellular metabolism of bacteria in (bio)fermentation processes is crucial to control and steer them, and to prevent undesired disturbances linked to metabolically inactive microorganisms. In this context, cell-based biosensors can play an important role to improve the quality and increase the yield of such processes. This work describes the simultaneous analysis of the metabolic behavior of three different types of bacteria by means of a differential light-addressable potentiometric sensor (LAPS) set-up. The study includes Lactobacillus brevis, Corynebacterium glutamicum, and Escherichia coli, which are often applied in fermentation processes in bioreactors. Differential measurements were carried out to compensate undesirable influences such as sensor signal drift, and pH value variation during the measurements. Furthermore, calibration curves of the cellular metabolism were established as a function of the glucose concentration or cell number variation with all three model microorganisms. In this context, simultaneous (bio)sensing with the multi-organism LAPS-based set-up can open new possibilities for a cost-effective, rapid detection of the extracellular acidification of bacteria on a single sensor chip. It can be applied to evaluate the metabolic response of bacteria populations in a (bio)fermentation process, for instance, in the biogas fermentation process.
Enzyme-catalyzed reactions have been designed to mimic various Boolean logic gates in the general framework of unconventional biomolecular computing. While some of the logic gates, particularly OR, AND, are easy to realize with biocatalytic reactions and have been reported in numerous publications, some other, like NXOR, are very challenging and have not been realized yet with enzyme reactions. The paper reports on a novel approach to mimicking the NXOR logic gate using the bell-shaped enzyme activity dependent on pH values. Shifting pH from the optimum value to the acidic or basic values by using acid or base inputs (meaning 1,0 and 0,1 inputs) inhibits the enzyme reaction, while keeping the optimum pH (assuming 0,0 and 1,1 input combinations) preserves a high enzyme activity. The challenging part of the present approach is the selection of an enzyme with a well-demonstrated bell-shape activity dependence on the pH value. While many enzymes can satisfy this condition, we selected pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase as this enzyme has the optimum pH center-located on the pH scale allowing the enzyme activity change by the acidic and basic pH shift from the optimum value corresponding to the highest activity. The present NXOR gate is added to the biomolecular “toolbox” as a new example of Boolean logic gates based on enzyme reactions.
Hydrogen peroxide (H2O2) is a typical surface sterilization agent for packaging materials used in the pharmaceutical, food and beverage industries. We use the finite-elements method to analyze the conceptual design of an in-line thermal evaporation unit to produce a heated gas mixture of air and evaporated H2O2 solution. For the numerical model, the required phase-transition variables of pure H2O2 solution and of the aerosol mixture are acquired from vapor-liquid equilibrium (VLE) diagrams derived from vapor-pressure formulations. This work combines homogeneous single-phase turbulent flow with heat-transfer physics to describe the operation of the evaporation unit. We introduce the apparent heat-capacity concept to approximate the non-isothermal phase-transition process of the H2O2-containing aerosol. Empirical and analytical functions are defined to represent the temperature- and pressure-dependent material properties of the aqueous H2O2 solution, the aerosol and the gas mixture. To validate the numerical model, the simulation results are compared to experimental data on the heating power required to produce the gas mixture. This shows good agreement with the deviations below 10%. Experimental observations on the formation of deposits due to the evaporation of stabilized H2O2 solution fits the prediction made from simulation results.
A light-addressable potentiometric sensor (LAPS) is a field-effect-based (bio-) chemical sensor, in which a desired sensing area on the sensor surface can be defined by illumination. Light addressability can be used to visualize the concentration and spatial distribution of the target molecules, e.g., H+ ions. This unique feature has great potential for the label-free imaging of the metabolic activity of living organisms. The cultivation of those organisms needs specially tailored surface properties of the sensor. O2 plasma treatment is an attractive and promising tool for rapid surface engineering. However, the potential impacts of the technique are carefully investigated for the sensors that suffer from plasma-induced damage. Herein, a LAPS with a Ta2O5 pH-sensitive surface is successfully patterned by plasma treatment, and its effects are investigated by contact angle and scanning LAPS measurements. The plasma duration of 30 s (30 W) is found to be the threshold value, where excessive wettability begins. Furthermore, this treatment approach causes moderate plasma-induced damage, which can be reduced by thermal annealing (10 min at 300 °C). These findings provide a useful guideline to support future studies, where the LAPS surface is desired to be more hydrophilic by O2 plasma treatment.
In modern bioanalytical methods, it is often desired to detect several targets in one sample within one measurement. Immunological methods including those that use superparamagnetic beads are an important group of techniques for these applications. The goal of this work is to investigate the feasibility of simultaneously detecting different superparamagnetic beads acting as markers using the magnetic frequency mixing technique. The frequency of the magnetic excitation field is scanned while the lower driving frequency is kept constant. Due to the particles’ nonlinear magnetization, mixing frequencies are generated. To record their amplitude and phase information, a direct digitization of the pickup-coil’s signal with subsequent Fast Fourier Transformation is performed. By synchronizing both magnetic beads using frequency scanning in magnetic frequency mixing technique magnetic fields, a stable phase information is gained. In this research, it is shown that the amplitude of the dominant mixing component is proportional to the amount of superparamagnetic beads inside a sample. Additionally, it is shown that the phase does not show this behaviour. Excitation frequency scans of different bead types were performed, showing different phases, without correlation to their diverse amplitudes. Two commercially available beads were selected and a determination of their amount in a mixture is performed as a demonstration for multiplex measurements.
For performing point-of-care molecular diagnostics, magnetic immunoassays constitute a promising alternative to established enzyme-linked immunosorbent assays (ELISA) because they are fast, robust and sensitive. Simultaneous detection of multiple biomolecular targets from one body fluid sample is desired. The aim of this work is to show that multiplex magnetic immunodetection based on magnetic frequency mixing by means of modular immunofiltration columns prepared for different targets is feasible. By calculations of the magnetic response signal, the required spacing between the modules was determined. Immunofiltration columns were manufactured by 3D printing and antibody immobilization was performed in a batch approach. It was shown experimentally that two different target molecules in a sample solution could be individually detected in a single assaying step with magnetic measurements of the corresponding immobilization filters. The arrangement order of the filters and of a negative control did not influence the results. Thus, a simple and reliable approach to multi-target magnetic immunodetection was demonstrated.
The movement of magnetic beads due to a magnetic field gradient is of great interest in different application fields. In this report we present a technique based on a magnetic tweezers setup to measure the velocity factor of magnetically actuated individual superparamagnetic beads in a fluidic environment. Several beads can be tracked simultaneously in order to gain and improve statistics. Furthermore we show our results for different beads with hydrodynamic diameters between 200 and 1000 nm from diverse manufacturers. These measurement data can, for example, be used to determine design parameters for a magnetic separation system, like maximum flow rate and minimum separation time, or to select suitable beads for fixed experimental requirements.
Sensitive and rapid detection of cholera toxin subunit B using magnetic frequency mixing detection
(2019)
Cholera is a life-threatening disease caused by the cholera toxin (CT) as produced by some Vibrio cholerae serogroups. In this research we present a method which directly detects the toxin’s B subunit (CTB) in drinking water. For this purpose we performed a magnetic sandwich immunoassay inside a 3D immunofiltration column. We used two different commercially available antibodies to capture CTB and for binding to superparamagnetic beads. ELISA experiments were performed to select the antibody combination. The beads act as labels for the magnetic frequency mixing detection technique. We show that the limit of detection depends on the type of magnetic beads. A nonlinear Hill curve was fitted to the calibration measurements by means of a custom-written python software. We achieved a sensitive and rapid detection of CTB within a broad concentration range from 0.2 ng/ml to more
than 700 ng/ml.
Extracellular acidification is a basic indicator for alterations in two vital metabolic pathways: glycolysis and cellular respiration. Measuring these alterations by monitoring extracellular acidification using cell-based biosensors such as LAPS plays an important role in studying these pathways whose disorders are associated with numerous diseases including cancer. However, the surface of the biosensors must be specially tailored to ensure high cell compatibility so that cells can represent more in vivo-like behavior, which is critical to gain more realistic in vitro results from the analyses, e.g., drug discovery experiments. In this work, O2 plasma patterning on the LAPS surface is studied to enhance surface features of the sensor chip, e.g., wettability and biofunctionality. The surface treated with O2 plasma for 30 s exhibits enhanced cytocompatibility for adherent CHO–K1 cells, which promotes cell spreading and proliferation. The plasma-modified LAPS chip is then integrated into a microfluidic system, which provides two identical channels to facilitate differential measurements of the extracellular acidification of CHO–K1 cells. To the best of our knowledge, it is the first time that extracellular acidification within microfluidic channels is quantitatively visualized as differential (bio-)chemical images.
The enantioselective synthesis of α-hydroxy ketones and vicinal diols is an intriguing field because of the broad applicability of these molecules. Although, butandiol dehydrogenases are known to play a key role in the production of 2,3-butandiol, their potential as biocatalysts is still not well studied. Here, we investigate the biocatalytic properties of the meso-butanediol dehydrogenase from Bacillus licheniformis DSM 13T (BlBDH). The encoding gene was cloned with an N-terminal StrepII-tag and recombinantly overexpressed in E. coli. BlBDH is highly active towards several non-physiological diketones and α-hydroxyketones with varying aliphatic chain lengths or even containing phenyl moieties. By adjusting the reaction parameters in biotransformations the formation of either the α-hydroxyketone intermediate or the diol can be controlled.
Coronavirus disease 2019 (COVID-19) is a novel human infectious disease provoked by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently, no specific vaccines or drugs against COVID-19 are available. Therefore, early diagnosis and treatment are essential in order to slow the virus spread and to contain the disease outbreak. Hence, new diagnostic tests and devices for virus detection in clinical samples that are faster, more accurate and reliable, easier and cost-efficient than existing ones are needed. Due to the small sizes, fast response time, label-free operation without the need for expensive and time-consuming labeling steps, the possibility of real-time and multiplexed measurements, robustness and portability (point-of-care and on-site testing), biosensors based on semiconductor field-effect devices (FEDs) are one of the most attractive platforms for an electrical detection of charged biomolecules and bioparticles by their intrinsic charge. In this review, recent advances and key developments in the field of label-free detection of viruses (including plant viruses) with various types of FEDs are presented. In recent years, however, certain plant viruses have also attracted additional interest for biosensor layouts: Their repetitive protein subunits arranged at nanometric spacing can be employed for coupling functional molecules. If used as adapters on sensor chip surfaces, they allow an efficient immobilization of analyte-specific recognition and detector elements such as antibodies and enzymes at highest surface densities. The display on plant viral bionanoparticles may also lead to long-time stabilization of sensor molecules upon repeated uses and has the potential to increase sensor performance substantially, compared to conventional layouts. This has been demonstrated in different proof-of-concept biosensor devices. Therefore, richly available plant viral particles, non-pathogenic for animals or humans, might gain novel importance if applied in receptor layers of FEDs. These perspectives are explained and discussed with regard to future detection strategies for COVID-19 and related viral diseases.
Electrolyte-insulator-semiconductor (EIS) field-effect sensors belong to a new generation of electronic chips for biochemical sensing, enabling a direct electronic readout. The review gives an overview on recent advances and current trends in the research and development of chemical sensors and biosensors based on the capacitive field-effect EIS structure—the simplest field-effect device, which represents a biochemically sensitive capacitor. Fundamental concepts, physicochemical phenomena underlying the transduction mechanism and application of capacitive EIS sensors for the detection of pH, ion concentrations, and enzymatic reactions, as well as the label-free detection of charged molecules (nucleic acids, proteins, and polyelectrolytes) and nanoparticles, are presented and discussed.
LAPS-based monitoring of metabolic responses of bacterial cultures in a paper fermentation broth
(2020)
As an alternative renewable energy source, methane production in biogas plants is gaining more and more attention. Biomass in a bioreactor contains different types of microorganisms, which should be considered in terms of process-stability control. Metabolically inactive microorganisms within the fermentation process can lead to undesirable, time-consuming and cost-intensive interventions. Hence, monitoring of the cellular metabolism of bacterial populations in a fermentation broth is crucial to improve the biogas production, operation efficiency, and sustainability. In this work, the extracellular acidification of bacteria in a paper-fermentation broth is monitored after glucose uptake, utilizing a differential light-addressable potentiometric sensor (LAPS) system. The LAPS system is loaded with three different model microorganisms (Escherichia coli, Corynebacterium glutamicum, and Lactobacillus brevis) and the effect of the fermentation broth at different process stages on the metabolism of these bacteria is studied. In this way, different signal patterns related to the metabolic response of microorganisms can be identified. By means of calibration curves after glucose uptake, the overall extracellular acidification of bacterial populations within the fermentation process can be evaluated.