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Bernhard Wolf

Publications and source records attributed to Bernhard Wolf.

8 recordsLinked to original sources
PubMed2006

Electric cell-substrate impedance sensing with screen printed electrode structures.

Impedance sensors in thick film technology have been tested as a tool for electric cell-substrate impedance sensing. The screen printed Pt electrodes have a width of 250-400 microm. Electrodes and the surrounding ceramic chip substrate could be homogeneously grown with L-929 and Hela cells. The performance of a screen printed interdigitated electrode structure (IDES) was compared with that of thin film structures with the same layout geometry. The thick film impedance sensors allowed to correctly record the morphological response of confluent Hela cell layers to stimulation with histamine. A thick film conductivity sensor also revealed impedance values which were dependent on cell growth on the electrode surface, even at a very low frequency range of approximately 1 Hz.

Animals↗
PubMed2006

Multiparametric sensor-chip based technology for monitoring metabolic activity: A proof-of-principle study with live tissue.

The recent development of an electronic test system based on silicon sensor-chips allows the continuous parallel recording of relative changes in extracellular acidification, oxygen consumption and electric impedance in living cells. The objective of this proof-of-principle study therefore, was to clarify whether this system can also be applied to live tissue slices thus providing a device for an ultimately envisioned chemosensitivity testing apparatus for individualized treatment schemes in cancer therapy. A prototype of the testing apparatus equipped with six individual measuring devices has been used to simultaneously analyze changes in extracellular acidification, oxygen consumption and electronic impedance in live liver tissue and compared to data obtained from a tumor cell line. In contrast to tumor cells, tissue slices showed low rates of extracellular acidification but high rates of oxygen consumption. Monitoring of electrical impedance values, reflecting cellular morphology, revealed that the compact cell structure of the tissue slices was able to function as electric insulator and actively change the impedance values of the system. Exposure of tumor cells to 1 microM cytochalasin B, a fungal metabolite known to interact with the cytoskeleton and influence glucose metabolism, resulted in the rapid decline of extracellular acidification, increased oxygen consumption rates and increased values in capacitance. In tissue slices upon addition of 1 microM cytochalasin B, a decline of both extracellular acidification and electrical impedance was observed within 1 h. Determination of ATP content in the tissue slices revealed that decreasing ATP content paralleled diminishing oxygen consumption. This new technique offers the possibility of generating metabolic profiles for cells and tissues by studying oxygen consumption, extracellular acidification and electrical impedance.

Acid-Base Equilibrium↗
PubMed2004

Analysis of drug action on tumor cell metabolism using electronic sensor chips.

Chemotherapeutic drugs affect the metabolism of tumor cells regardless of the specific target of action. Basic parameters of cell metabolism are extrusion of acids into the microenvironment and oxygen consumption. To analyze these changes on living cells in real-time, a test system based on multiparametric chips with an array of sensors for monitoring pH and O(2) as well as electric impedance has been developed. Cells are cultivated on these chips and supplied with medium by a fluid perfusion set-up which mimics microphysiological conditions and allows for drug addition and removal. Human colon carcinoma cells LS174T were used as a model to test the effect of drugs. Cells growing on chips were monitored for 24 h and longer. Untreated cells showed a continuous increase in the rate of acidification, while the rate of respiration remained fairly constant. Addition of chloroacetaldehyde (50 microM) rapidly attenuated O(2) consumption with a gradual decrease in acidification following. In contrast, with cisplatin (16.7 microM) a delayed and gradual decrease in both the rates of acidification and respiration effect occurred over 2-3 days. These results provide insights to the mechanisms of action of these drugs, which are coherent with those already known. Thus, multiparametric sensor chips provide elementary information on drug action.

Antineoplastic Agents↗
PubMed2004

Relevance of tumor microenvironment for progression, therapy and drug development.

Tumor interstitium exhibits a microenvironment that differs from corresponding normal tissues. Tumor phenotype shows, for example, an elevated intracellular pH (pHi), a lowered extracellular pH (pHe), a low oxygen concentration and low glucose levels. These differences are caused by cell biological (so called intrinsic) factors, e.g. a higher acidification rate, as well as by more systemic (extrinsic) factors, e.g. poor tumor vascularization. They represent important factors for invasiveness, immune suppression and proliferation, and they imply possibilities for diagnosis, prognosis and therapy. We have developed an experimental data-based computer model, which has simulated the potential role of metabolic effects on tumor progression. We show an experiment on cellular metabolism demonstrating the immunosuppressive impact of low pHe on peripheral blood mononuclear cells. Finally, we review important findings on the tumor microenvironment leading to possibilities for therapy which are currently evolving and which promise higher effectiveness for cancer therapy.

Cell Hypoxia↗
PubMed2004

[Chips instead of mice: cells on bioelectronic sensor-chips as an alternative to animal experiments].

An alternative assay for replacing animal experiments should serve the specific microphysiological needs of the cells and be endowed with multiparametric signal monitoring. These requirements are provided by a test system in which the key elements are biocompatible electronic sensor-chips. It is also connected to a medium perfusion set-up, which allows to control the supply of nutrients and test compounds, and the removal of culture medium. The chips are equipped with sensors that continuously monitor basic metabolic parameters and membrane-associated changes of living cells: pH-ISFETs for extracellular acidification, amperometric O2-sensors for oxygen consumption, and IDES for electrical impedance of the cell layer. Experiments with LS174T colon carcinoma cells in culture show the metabolic and electrical changes upon incubation with Zytochalasin B and chloroacetaldehyde. The signal patterns vary and indicate different mechanisms of action for these test compounds. With this test system it is possible to detect effects of unknown substances and mixtures, and to analyse the cellular probe for prolonged times.

Animal Testing Alternatives↗
PubMed2003

Multiparametric sensor chips for chemosensitivity testing of sensitive and resistant tumor cells.

Many different assays have been developed for testing the chemosensitivity of tumor cells in vitro, usually based on a single biochemical or cellular parameter. A multiparametric test system has been developed that accommodates on a single chip numerous sensors for metabolic parameters, deltapH and deltapO2, as well as for morphological changes. The cells grow directly on the chips and can be continuously monitored online up to several days. The effects of various chemotherapeutic drugs on the metabolic profile of several tumor cell lines have been investigated. In colon carcinoma-derived LS174T cells, cytochalasin B markedly increased oxygen consumption while decreasing the rate of extracellular acidification. These effects, which reflect the biochemical action of cytochalasin B, were reversible on drug removal. In contrast, chloroacetaldehyde markedly reduced respiration, which recovered when the drug was removed. Primary breast cancer cells also responded to chloroacetaldehyde with a marked reduction in deltapO2, followed by a reduced rate of acidification. Comparing the metabolism of doxorubicin-sensitive and -resistant mouse sarcoma S180 cells, the rates of acidification and respiration were inhibited by doxorubicin only in the sensitive cells, whereas in the resistant cells oxygen consumption even increased. These examples demonstrate that this chip-based test system provides rapid and important information for assessing chemosensitivity of tumor cells.

Acetaldehyde↗
PubMed2003

Microphysiological testing for chemosensitivity of living tumor cells with multiparametric microsensor chips.

A constraint in the reliability of predictive chemosensitivity assays is linked to the fact that they analyze only a single cellular or biochemical parameter. A multiparametric test system using microsensor chips has been developed which can detect online microphysiological changes in living cells. Tumor cells were grown directly on glass- or silicon-based electronic sensor chips. Changes in extracellular pH and pO(2), reflecting metabolic activities, and changes in impedance, reflecting morphological properties, were monitored. In this study, colon and breast cancer cells as well as doxorubicin-sensitive and doxorubicin-resistant sarcoma cell lines were exposed to cytochalasin B, chloroacetaldehyde, or doxorubicin. Results show (1) reduction in medium acidification, (2) marked and rapid changes in O(2) consumption, and (3) modulations in impedance correlating with morphological changes observed in the microscope. Drug-resistant cells do not show these changes. Therefore, this microphysiological monitoring is a versatile tool for chemosensitivity testing of tumor cells.

Antineoplastic Agents↗