Unexpected adverse effects on the cardiovascular system remain a major challenge in the development of novel active pharmaceutical ingredients (API). To overcome the current limitations of animal-based in vitro and in vivo test systems, stem cell derived human cardiomyocyte clusters (hCMC) offer the opportunity for highly predictable pre-clinical testing. The three-dimensional structure of hCMC appears more representative of tissue milieu than traditional monolayer cell culture. However, there is a lack of long-term, real time monitoring systems for tissue-like cardiac material. To address this issue, we have developed a microcavity array (MCA)-based label-free monitoring system that eliminates the need for critical hCMC adhesion and outgrowth steps. In contrast, feasible field potential derived action potential recording is possible immediately after positioning within the microcavity. Moreover, this approach allows extended observation of adverse effects on hCMC. For the first time, we describe herein the monitoring of hCMC over 35 days while preserving the hCMC structure and electrophysiological characteristics. Furthermore, we demonstrated the sensitive detection and quantification of adverse API effects using E4031, doxorubicin, and noradrenaline directly on unaltered 3D cultures. The MCA system provides multi-parameter analysis capabilities incorporating field potential recording, impedance spectroscopy, and optical read-outs on individual clusters giving a comprehensive insight into induced cellular alterations within a complex cardiac culture over days or even weeks.
Wound infection status is a relevant diagnostic parameter to enhance wound treatment towards better healing rate. Impedance evaluation is a powerful tool to measure the inflammatory response like the released DNA of neutrophils. In our research we investigated the dielectric behaviour of neutrophils settled on electrodes in vitro. The cells have been stimulated to react in the same way as in a wound infection. The result is a significant impedance deviation of about 50 % with comparable amount of cells like in an infected wound. Microscopic fluorescence verifications acknowledge these findings.
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.
Biofilm formation can cause serious health hazards, mostly due to the uncontrolled release of pathogens. This can generate several problems in industrial facilities, e.g., in the food industry. The aim of the present study was to develop and implement a multi-parametric sensor system to monitor biofilm formation in laboratory as well as industrial set-ups. To minimize cross sensitivity or interference, the device was based on a combination of different measurement principles. Micro-organisms were initially cultivated in a laboratory scale reactor. Afterwards, biofilm formation will be studied with each prototype of the multi-parametric sensor followed by final tests on an industrial scale.
Quantitative impedimetric NPY-receptor activation monitoring and signal pathway profiling in living cells
Label-free and non-invasive monitoring of receptor activation and identification of the involved signal pathways in living cells is an ongoing analytic challenge and a great opportunity for biosensoric systems. In this context, we developed an impedance spectroscopy-based system for the activation monitoring of NPY-receptors in living cells. Using an optimized interdigital electrode array for sensitive detection of cellular alterations, we were able for the first time to quantitatively detect the NPY-receptor activation directly without a secondary or enhancer reaction like cAMP-stimulation by forskolin. More strikingly, we could show that the impedimetric based NPY-receptor activation monitoring is not restricted to the Y1-receptor but also possible for the Y2- and Y5-receptor. Furthermore, we could monitor the NPY-receptor activation in different cell lines that natively express NPY-receptors and proof the specificity of the observed impedimetric effect by agonist/antagonist studies in recombinant NPY-receptor expressing cell lines. To clarify the nature of the observed impedimetric effect we performed an equivalent circuit analysis as well as analyzed the role of cell morphology and receptor internalization. Finally, an antagonist based extensive molecular signal pathway analysis revealed small alterations of the actin cytoskeleton as well as the inhibition of at least L-type calcium channels as major reasons for the observed NPY-induced impedance increase. Taken together, our novel impedance spectroscopy based NPY-receptor activation monitoring system offers the opportunity to identify signal pathways as well as for novel versatile agonist/antagonist screening systems for identification of novel therapeutics in the field of obesity and cancer.
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.
The development of biosensors to identify the molecular markers of specific genes is fundamental for the implementation of new techniques that allow the detection of specific DNA sequences in a fast, economic, and simple way. Electrical Bioimpedance Spectroscopy (EBiS) has been used for the diagnosis and monitoring of human pathologies, and is recognized as a safe, fast, reusable, easy, and inexpensive technique. This study proves the development of a complementary DNA (cDNA) biosensor based on measurements of EBiS and of the immobilization of DNA without chemical modifications, and presents the evaluation of its potential usefulness in the detection of the gene expression of an inflammation characteristic biomarker, NLRP3, is presented. The obtained results demonstrate that EBiS can be used to identify different gene expression patterns, and measurements were compared with Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) and validated by Quantitative Polymerase Chain Reaction (qPCR). These results indicate the technical feasibility of a biosensor of specific genes through bioimpedance measurements in the immobilization of cDNA.
Im Wachstumskern „Biologische Sensor-Aktor-Systeme auf der Basis von funktionalisierten Mikroorganismen (BioSAM)“ werden Ganzzellsensoren für die Umwelt- und Medizintechnik entwickelt, welche die Reaktion lebender Zellen auf umwelt- oder prozessrelevante Stoffe zur Bewertung der biologischen Wirkung von Analyten nutzen. Im Teilvorhaben HIGS („Hochintegrierte Ganzzellsensoren für die Umwelt- und Medizintechnik“) werden dabei gentechnisch modifizierte Hefezellen eingesetzt, die bei Anwesenheit des Analyten Diclofenac, welches als anthropogener Spurenstoff in Wässern vorkommt, ein Fluoreszenzprotein produzieren. In der vorliegenden Arbeit werden verschiedene Aspekte des entwickelten Ganzzellsensors dargestellt. Im ersten Teil wird der mikrofluidische Aufbau zur sicheren Einhausung der Hefezellen vorgestellt, der einen optischen Zugang zur Detektion des Fluoreszenzsignales gewährleistet und gleichzeitig die Versorgung der Hefezellen mit Nährmedium und Analyt sicherstellt. Mit diesem Aufbau können Diclofenac-Konzentrationen zwischen 10 und 100 µM in Nährmedium unterschieden werden. Im zweiten Teil dieser Arbeit wird vorgestellt, wie die optische Detektion des Fluoreszenzsignals mit Impedanzmessungen kombiniert wurde. Ein Sensormodell auf der Basis elektrischer Netzwerke wurde entwickelt, welches das dynamische Verhalten der immobilisierten Zellen und die Transportprozesse an den Elektroden beschreibt.
Lab-on-a-chip devices that combine, e.g. chemical synthesis with integrated on-chip analytics and multi-compartment organ-on-a-chip approaches, are a fast and attractive evolving research area. While integration of appropriate cell models in microfluidic setups for monitoring the biological activity of synthesis products or test compounds is already in focus, the integration of label-free bioelectronic analysis techniques is still poorly realized. In this context, we investigated the capabilities of impedance spectroscopy as a non-destructive real-time monitoring technique for adherent cell models in a microfluidic setup. While an initial adaptation of a microelectrode array (MEA) layout from a static setup revealed clear restrictions in the application of impedance spectroscopy in a microfluidic chip, we could demonstrate the advantage of a FEM simulation based rational MEA layout optimization for an optimum electrical field distribution within microfluidic structures. Furthermore, FEM simulation based analysis of shear stress and time-dependent test compound distribution led to identification of an optimal flow rate. Based on the simulation derived optimized microfluidic MEA, comparable impedance spectra characteristics were achieved for HEK293A cells cultured under microfluidic and static conditions. Furthermore, HEK293A cells expressing Y1 receptors were used to successfully demonstrate the capabilities of impedimetric monitoring of cellular alterations in the microfluidic setup. More strikingly, the maximum impedimetric signal for the receptor activation was significantly increased by a factor of 2.8. Detailed investigations of cell morphology and motility led to the conclusion that cultivation under microfluidic conditions could lead to an extended and stabilized cell–electrode interface.
El desarrollo de biosensores para identificar marcadores moleculares es fundamental para la implementación de nuevas técnicas que permitan la detección de mutaciones genéticas de manera rápida, económica y simple. En este estudio se presenta el desarrollo de un biosensor de ADN complementario (cADN) basado en mediciones de espectroscopía de bioimpedancia eléctrica, y se evalúa su potencial utilidad en la detección de un gen característico de obesidad. Los resultados indican la factibilidad técnica de desarrollar un biosensor de marcadores moleculares o genes específicos a través de la inmovilización de cADN y su detección con mediciones de espectroscopía de bioimpedancia eléctrica.