Agilent xCELLigence RTCA DP - Cell Invasion & Migration

RTCA Analyzer

Overview

The xCELLigence RTCA DP (dual purpose) instrument is unique in the ability to make continuous measurements of cell invasion and migration (CIM) using an electronically integrated Boyden chamber. The instrument uses electrical impedance monitoring to quantify changes with a label-free methodology. The three cradles of the DP instrument enable three separate electronic 16-well plates to be controlled and monitored in parallel or independently of one another. This flexible plate batch processing allows maximum productivity for multiple users. The instrument operates in a standard CO2 cell culture incubator and the control unit is housed outside the incubator.

• Perform real-time cell invasion and migration assays using CIM-Plate, an electronically integrated Boyden chamber
• Obtain thousands of time points during your cell migration assay
• RTCA provides a quantitative readout of cell number, proliferation rate, cell size/shape, and cell-substrate attachment quality



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Agilent xCELLigence RTCA DP - Cell Invasion & Migration



The xCELLigence RTCA DP system is comparable to all other xCELLigence RTCA system and offers some extra capabilities too! The instrument is unique in its capability to use electrical impedance to quantify Cell Invasion and Migration (CIM). The electronically integrated Boyden chamber gives a signal that correlates with the degree of cell migration/invasion. It enables researchers to run 3 x 16 well plates independently in a label-free manner. The instrument operates in a standard CO2 cell culture incubator and the control unit is housed outside the incubator. Easy-to-use intuitive software allows for real-time control and monitoring of the instrument and includes real-time data display and analysis functions.

Typical Applications
• Cancer immunotherapy:
With the monitoring of cell killing

• Virology & Infectious diseases:
Monitor pathogens behaviour

• Cell Invasion & Migration:
Due to the integrated Boyden chambers

• Cytotoxicity Overview:
Monitor cell behaviour and attachment to the plate surface

• Stem Cell Differentiation:
Capture the process of stem cells differentiating into somatic cells

• Cell Adhesion:
Studying cell adhesion and cell spreading

Cellular Impedance Explained
Positioned between reductionistic biochemical assays and whole organism in vivo experimentation, cell-based assays serve as an indispensable tool for basic and applied biological research. However, the utility of many cell-based assays is diminished by: (1) the need to use labels, (2) incompatibility with continuous monitoring (i.e. only end point data is produced), (3) incompatibility with orthogonal assays, and (4) the inability to provide an objective/quantitative readout. Each of these shortcomings is, however, overcome by the non-invasive, label-free, and real-time cellular impedance assay.



Functional Unit of Cellular Impedance Assay
The functional unit of a cellular impedance assay is a set of gold microelectrodes fused to the bottom surface of a microtiter plate well (Figure 1). When submersed in an electrically conductive solution (such as buffer or standard tissue culture medium), the application of an electric potential across these electrodes causes electrons to exit the negative terminal, pass through bulk solution, and then deposit onto the positive terminal to complete the circuit. Because this phenomenon is dependent upon the electrodes interacting with bulk solution, the presence of adherent cells at the electrode-solution interface impedes electron flow. The magnitude of this impedance is dependent on the number of cells, the size and shape of the cells, and the cell-substrate attachment quality. Importantly, neither the gold microelectrode surfaces nor the applied electric potential (22 mV) have an effect on cell health or behavior.
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Impedance Electrodes
The gold microelectrode biosensors in each well of ACEA’s electronic microtiter plates (E-Plates®) cover 70-80% of the surface area (depending if a view area is present). Rather than the simplified electrode pair depicted in Figure 1, the electrodes in each well of an E-Plate are linked into “strands” that form an interdigitating array (Figure 2). This arrangement enables populations of cells to be monitored simultaneously and thereby provides exquisite sensitivity to: the number of cells attached to the plate, the size/morphology of the cells, and the cell-substrate attachment quality.

Figure Left: Impedance electrodes on ACEA’s E-Plates. (A) Simplified schematic of the interdigitated electrodes used in each well of an E-Plate. Electrodes are not drawn to scale (only a few are shown, and they have been enlarged for clarity). Though cells can also be visualized on the gold electrode surfaces, the electrode-free region in the middle of the well facilitates microscopic imaging (brightfield, fluorescence, etc.). (B) Photograph of a single well in a 96-well E-Plate. (C) Zoomed in brightfield image of shadowed electrodes and unstained human cells. (D) Gold electrodes and crystal violet stained human cells, as viewed in a compound microscope.


Real-Time Impedance Traces Explained
The impedance of electron flow caused by adherent cells is reported using a unitless parameter called Cell Index (CI), where CI = (impedance at time point n – impedance in the absence of cells)/nominal impedance value. Figure 3 provides a generic example of a real-time impedance trace throughout the course of setting up and running an apoptosis experiment. For the first few hours after cells have been added to a well there is a rapid increase in impedance. This is caused by cells falling out of suspension, depositing onto the electrodes, and forming focal adhesions. If the initial number of added cells is low and there is empty space on the well bottom cells will proliferate, causing a gradual yet steady increase in CI. When cells reach confluence the CI value plateaus, reflecting the fact that the electrode surface area that is accessible to bulk media is no longer changing. The addition of an apoptosis inducer at this point causes a decrease in CI back down to zero. This is the result of cells rounding and then detaching from the well bottom. While this generic example involves drug addition when cells are confluent, impedance-based assays are extremely flexible and can also evaluate the rate and extent of initial cell adhesion to the electrodes, or the rate and extent of cell proliferation.


Figure Right: Generic real-time impedance trace for setting up and running an apoptosis assay. Each phase of the impedance trace, and the cellular behavior it arises from, is explained in the text.
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Correlating Impedance with Cellular Phenomena
RTCA provides a quantitative readout of cell number, proliferation rate, cell size/shape, and cell-substrate attachment quality. Because these physical properties are the product of thousands of different genes/proteins, RTCA can provide an extremely wide field of view on cell health and behavior. Everything from endothelial barrier function and chemotaxis to filopodia dynamics and immune cell-mediated cytolysis have successfully been analyzed on xCELLigence instruments. Despite the breadth of their reach, xCELLigence assays are still capable of interrogating very specific biochemical and cellular phenomena. Appropriate use of controls and/or orthogonal techniques make it possible to correlate the features of an impedance trace with specific cellular/molecular phenomena. To learn more about how this is done, and to witness the sensitivity and versatility of the xCELLigence RTCA technology, peruse the many specific applications that are highlighted here.

Figure Left: Examples of real-time impedance traces obtained using E-Plates and xCELLigence RTCA instruments. (A) Real-time monitoring of A549 cell adhesion to E-Plate wells that had been pre-coated with different concentrations of collagen IV. Note the correlation between impedance values (Cell Index) and the number of adherent cells visible in the microscope. (B) Real-time impedance traces for HeLa cells exposed to different concentrations of the GPCR agonist dopamine. The black arrow indicates the time of dopamine addition. (C) Real-time impedance traces for NK 92 cell-mediated cytolysis of MCF7 breast cancer cells. (D) Real-time impedance traces for A549 cells exposed to drugs displaying a variety of mechanisms of action.
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Cell invasion and migration plate

The cell invasion and migration plate (CIM-Plate 16) is a 16-well electronically integrated Boyden chamber, composed of upper and lower chambers that snap together (Figure 2). Pressure-sensitive silicone O-rings are present in the lower chamber to ensure a tight seal between the upper and lower chambers for each well (Figure 2C). A PET microporous membrane serves as the base of the upper chamber, allowing cells to translocate towards chemoattractant in the lower chamber (Figure 2B). The bottom side of the membrane is coated with gold biosensors (Figure 2B) that have an ability to detect the reduced electric current when cells adhere to their surface. This “impedance” signal enables a quantitative kinetic measurement of cell movement from the upper chamber to the lower chamber.

CIM-Plate overview. (A) CIM-Plate components. (B) A fully assembled CIM-Plate in detail. The expanded view illustrates the upper and lower chambers of a single well. Cells can migrate through the bottom membrane of the upper chamber and gold electrodes on the underside of this membrane detect the presence of adherent cells. (C) Gold biosensors are coated in the bottom surface of the upper chamber, composed of a PET microporous membrane. For a simple migration assay (not illustrated here), the cells being monitored would be plated directly onto the membrane. For an invasion assay (shown here), cells are plated on top of either the basement membrane matrix or a monolayer of cells.





Cancer Immunotherapy
Immune cell-mediated tumor cell killing can involve the components of both the innate and adaptive immune systems, including natural killer (NK) cells, cytotoxic T cells (MHC-dependent), antibodies secreted by B lymphocytes, engineered antibodies such as bispecific antibodies and bispecific T cell engagers (BiTEs), and genetically engineered T cells targeting specific tumor antigens (e.g., CAR-T, MHC-independent). The xCELLigence Real-Time Cell Analysis (RTCA) instrument monitors cell killing in real time. Simply add target and immune effector cells to the patented microplates (E-Plates), load the instrument, and start reading.
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Virology & Infectious Diseases
Study pathogen fitness and behavior in real-time by using xCELLigence Real-Time Cell Analysis (RTCA) instruments. Continuously monitor viral infections and bacterial biofilms in an automated, non-invasive, and label-free manner.
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Cell Invasion & Migration
Cell invasion and migration is critical to many facets of biology, including processes such as wound healing and the intravasation/extravasation of cancer cells during metastasis. A major hurdle to studying migration and invasion is the lack of techniques that are quantitative, reproducible, and efficient. Agilent's cell invasion and migration platform (CIM-Plate used with the xCELLigence RTCA DP system) contains biosensor integrated Boyden chambers that provide real-time, label-free continuous monitoring of cell migration/invasion with minimal reqired setup.
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Cytotoxicity Overview
xCELLigence real time cell analysis (RTCA) uses biosensors on the bottom of E-Plate wells to continuously monitior the number of cells present, their size/morphology, and how tightly they are interacting with the plate surface. Cytotoxic responses nearly always involve biochemical changes that directly, or indirectly, affect one or more of the these parameters. Consequently, xCELLigence is able to monitor cytotoxic responses resulting from an exceptionally wide range of molecular targets (Figure 1).
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Stem Cell Differentiation
xCELLigence Real-Time Cell Analysis captures the process of differentiating stem cells into somatic cells. The kinetics of changes in real time and provide quantitative assessment of cell morphology, membrane potential, metabolic activity, and responsiveness to certain signals.
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Cell Adhesion
xCELLigence Real-Time Cell Analysis (RTCA) instrument continuously monitor cell adhesion and spreading without any manipulation of cells. Study interactions between extracellular matrix (ECM) proteins and cell surface integrins in an automated, non-invasive, and label-free manner.
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Analyzer Application Adhesion Apoptosis Cell Characterization
Cytotoxity Immune Cell Killing Proliferation
Receptor Signaling Stem Cells Virus Cytopathic Effects
  Cell Invasion & Migration
Depth 22.5 cm
Height 22.5 cm
Operating Environment Relative Humidity 5-98 %
Operating Environment Temperature 20-40 °C
Sampling Format 3 x 16 well plates
Width 24 cm