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Miniaturized wound sensors based on detection of extracellular chromatin
Sensors for monitoring wound infections are important to improve care management especially for chronic wounds. As detection parameter the formation of extracellular chromatin was chosen which has characteristic dielectric properties in ionic solvents due to its bound negative charges. Experiments with planar electrodes resulted in a high impedance increase of nearly 450%. The analysis of the relative permittivity revealed a cut-off frequency at 5 kHz. It is shown for the very first time that the changing electrical medium properties during Neutrophil Extracellular Traps (NET) formation are relevant for the occurring dispersion. A textile sensor set-up is proposed to fulfill the requirements of miniaturization and bio-compatibility. With these experimental results it is possible to design a fiber-based sensor based on an impedance detection principle.
Measuring the viscosity of glycerin solutions in very small samples using Sciospec ISX-3 Impedance Analyzer
Measuring the viscosity of very small sample volumes is of high interest in many fields especially in miniaturized and micro-fluidic systems. This application note describes an approach using the change of the impedance spectrum of a Thickness Shear Mode Resonator in combination with a sophisticated fitting algorithm. The simple setup of the measuring system enables easy integration in existing micro-fluidic settings with almost no adaption. As validation of the Sciospec ISX-3 a comparison to theoretical values and to a commercially available vector network analyzer on the same setup is provided.
The measurement of the viscosity is very well known for sample volumes larger than a couple milliliters. The standard viscometers use either rotating parts, a flow through, a capillary system or falling spheres. This application note describes an example of measuring smaller sample volumes with no need for mechanical parts.
512 channel system for in-depth insights into complex cell electrophysiology
Infection Monitoring in Wounds
Wound infection monitoring is a challenging task. It is only solvable by designing an integrable and cost-efficient sensor which measures a relevant set of parameters. One viable parameter is the formation of neutrophil extracellular traps (NETs). Their task is trapping pathogens in the wound. A wound infection results in massive release of them which can be detected with impedimetric methods. Our investigations focused on the characterization of the biological process with an in vitro model. The model environment is a cell culture with neutrophil granulocytes cultured on interdigitated electrodes which represent the sensor surface. Detected impedance changes caused by NET-formation were in the range of 35% and even higher. This implies that impedance measurements are suitable for NET detection. We derived a measurement and evaluated it by differing conditions like changing stimulation agent and varying the cell number. For both conditions the results of impedance and phase angle deviation can be confirmed. In combination with other parameters a sensor can be designed for specific detection of wound infections. These aspects are integrated in our sensor concept.
