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Oberschleißheim, Germany

Pfister C.,TU Munich | Wolf P.,HP Medizintechnik GmbH
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS

We present an automated analysis of the cellular dynamic metabolic activity in combination with live cell imaging, an essential factor for understanding the fundamental cellular physiological responses. For that purpose, we utilized the Intelligent Microplate Reader, a new analysis platform for marker-free cell-based assays in real-time. To demonstrate the benefit of the platform, we analyzed the relationship between various dynamic cell parameters (extracellular acidification, oxygen uptake, cell morphology, cell density and cell migration) of L929, a mouse fibroblast cell line, under the influence of sodium dodecyl sulfate. The dynamic kinetics of the monitored parameters are consistent and revealing much information about the activity occurring in the cells. © 2015 IEEE. Source

Demmel F.,TU Munich | Brischwein M.,TU Munich | Wolf P.,HP Medizintechnik GmbH | Huber F.,TU Munich | And 2 more authors.
Physiological Measurement

The response of two well-characterized human breast cancer cell lines (MCF-7 and MDA-MB-231) to a series of nutrient deficiencies is investigated with a label-free cell assay platform. The motivation of the research is to analyze adaptive responses of tumor cell metabolism and to find limiting conditions for cell survival. The platform measures extracellular values of pH and dissolved oxygen saturation to provide data of extracellular acidification rates and oxygen uptake rates. Additional electric cell substrate impedance sensing and bright-field cell imaging supports the data interpretation by providing information about cell morphological parameters. A sequential administration of nutrient depletions does not cause metabolic reprogramming, since the ratios of oxygen uptake to acidification return to their basal values. While the extracellular acidification drops sharply upon reduction of glucose and glutamine, the oxygen uptake is not affected. In contrast to other published data, cell death is not observed when both glucose and glutamine are depleted and cell proliferation is not inhibited, at least in MCF-7 cultures. It is assumed that residual concentrations of nutrients from the serum component are able to maintain cell viability when delivered regularly by active flow like in the cell assay platform, and, in a similar way, under physiological conditions. © 2015 Institute of Physics and Engineering in Medicine. Source

Kleinhans R.,TU Munich | Brischwein M.,TU Munich | Wang P.,TU Munich | Becker B.,TU Munich | And 7 more authors.
Medical and Biological Engineering and Computing

Personalized tumor chemotherapy depends on reliable assay methods, either based on molecular ''predictive biomarkers'' or on a direct, functional ex vivo assessment of cellular chemosensitivity. As a member of the latter category, a novel high-content platform is described monitoring human mamma carcinoma explants in real time and label-free before, during and after an ex vivo modeled chemotherapy. Tissue explants are sliced with a vibratome and laid into the microreaction chambers of a 24-well sensor test plate. Within these ≈23 μl volume chambers, sensors for pH and dissolved oxygen record rates of cellular oxygen uptake and extracellular acidification. Robot-controlled fluid system and incubation are parts of the tissue culture maintenance system while an integrated microscope is used for process surveillance. Sliced surgical explants from breast cancerous tissue generate well-detectable ex vivo metabolic activity. Metabolic rates, in particular oxygen consumption rates have a tendency to decrease over time. Nonetheless, the impact of added drugs (doxorubicin, chloroacetaldehyde) is discriminable. Sensor-based platforms should be evaluated in explorative clinical studies for their suitability to support targeted systemic cancer therapy. Throughput is sufficient for testing various drugs in a range of concentrations while the information content obtained from multiparametric real-time analysis is superior to conventional endpoint assays. © International Federation for Medical and Biological Engineering 2011. Source

Pfister C.,TU Munich | Pfister C.,HP Medizintechnik GmbH | Forstmeier C.,TU Munich | Biedermann J.,TU Munich | And 6 more authors.
Medical and Biological Engineering and Computing

We estimated the dynamic cell metabolic activity and the distribution of the pH value and oxygen concentration in tissue samples cultured in vitro by using real-time sensor records and a numerical simulation of the underlying reaction–diffusion processes. As an experimental tissue model, we used chicken spleen slices. A finite element method model representing the biochemical processes and including the relevant sensor data was set up. By fitting the calculated results to the measured data, we derived the spatiotemporal values of the pH value, the oxygen concentration and the absolute metabolic activity (extracellular acidification and oxygen uptake rate) of the samples. Notably, the location of the samples in relation to the sensors has a great influence on the detectable metabolic rates. The long-term vitality of the tissue samples strongly depends on their size. We further discuss the benefits and limitations of the model. © 2015 International Federation for Medical and Biological Engineering Source

Pfister C.,TU Munich | Pfister C.,HP Medizintechnik GmbH | Bozsak C.,TU Munich | Wolf P.,HP Medizintechnik GmbH | And 3 more authors.
Physiological Measurement

Flow-induced shear stress on adherent cells leads to biochemical signaling and mechanical responses of the cells. To determine the flow-induced shear stress on adherent cells cultured in a micro-scaled reaction chamber, we developed a suitable finite element method model. The influence of the most important parameters - cell shape, cell density, shear modulus and fluid velocity - was investigated. Notably, the cell shape strongly influences the resulting shear stress. Long and smooth cells undergo lower shear stress than more rounded cells. Changes in the curvature of the cells lead to stress peaks and single cells experience higher shear stress values than cells of a confluent monolayer. The computational results of the fluid flow simulation were validated experimentally. We also analyzed the influence of flow-induced shear stress on the metabolic activity and shape of L929, a mouse fibroblast cell line, experimentally. The results indicate that threshold stress values for continuous flow conditions cannot be transferred to quasi static flow conditions interrupted by short fluid exchange events. © 2015 Institute of Physics and Engineering in Medicine. Source

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