Impedance cell proliferation

Besides ligand-induced signaling, other apphcations of this assay are the measurement of cell proliferation or cell viability (Kho et al., 2015). Chemotaxis can be measured in real time by combining this technique with the chemotaxis assay described in Section 3.2.6. Cells in the upper chamber of a CIM-plate migrate through the porous membrane into the chemoattractant-containing lower chamber and adhere to the microelectrode embedded in the bottom of the plate, leading to an increase in impedance (Iqbal et al., 2013). 

Non-excitable cells with no obvious electrical activity play the same important role as excitable cells in cell-based biosensors. The changes in electrical signals, such as cell impedance, and nonelectrical parameters such as cell morphology, proliferation, metabolism, cell viability, pH, and extracellular analyte concentrations, can be measured upon chemical exposure and physical stimuli. Cells can also be genetically engineered to express reporters or biomarkers, such as the green fluorescence protein (GFP), upon specific stimulation. 

Tumor hypoxia can dramatically impede the effectiveness of certain (passive) immunotherapies using cytokines (interferon-y and tumor necrosis factor-a). Hypoxia also reduces survival and proliferation of T-lymphocytes and the production of cytokines by these cells (Kim et al. 2008 Lukashev et al. 2007). Pharmacological studies have firmly established that high levels of adenosine, a pathophysiological feature of solid tumors (see Chap. 4, Sect. 4.11.12), have immunosuppressive effects (SiTKovsKY and Lukashev 2005 Ohta et al. 2006). In addition, hypoxia can alter IL-2-induced activation of lymphokine-activated killer (LAK) cells (reviewed by Chaplin et al. 2000 Kim et al. 2008 SiTKOVSKY and Lukashev 2005). The potency of treatment started to decrease at oxygen partial pressures of less than approximately 35 mmHg ( 5% O2). 

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