The real-time, label-free monitoring of cellular behavior, including adhesion, proliferation, migration, and response to external stimuli, provides valuable insights into various biological processes and drug effects. In cellular biology, an impedance-based assay can be used to measure those changes and effects in cells. To measure impedance, small electrical currents are delivered to electrodes embedded in the cell culture substrate. Initially, when no cells are present, the electrical current flows easily, resulting in low impedance. However, upon introducing cells onto the substrate, they obstruct these electrical currents, leading to an increase in impedance.

This technique enables the creation of cell-specific profiles, aiding in the observation of various proliferation and cell behavior patterns. Impedance is also sensitive to subtle changes in cell conformation, such as those caused by receptor-mediated signaling. If a perturbation causes cells to die or detach, the impedance decreases.

The AtlaZ device operates by assessing changes in the complex impedance of a cell monolayer, e.g. triggered by receptor stimulation, effector cells such as CAR-T cells or toxic compounds. The system provides quantitative live-cell analysis by analysing the Cell Signal (Impedance IZI in Ohm) of adherent cells grown on 96-well plates with embedded planar gold-film electrodes.

AtlaZ uses Electrical Impedance Spectroscopy (EIS) to record a full spectrum of cell signals, thus providing a unique richness of information from cells. Depending on the data acquisition frequency, the system detects predominantly the resistive part of cell-cell and cell-matrix contacts at lower frequencies or predominantly capacitive currents across the cell membranes at higher frequencies as an indicator for electrode coverage. The latter is the basis for cell adhesion or migration assays. Thus, impedance data provide insights into various cell phenotypes, such as cell morphology changes as a result of signaling, proliferation, lateral migration or cytotoxicity in real-time and over prolonged periods of time.

The optimal recording frequency varies depending on the cell type and is determined empirically. Typically, it falls between 1 kHz and 50 kHz for most target cells as adhered to AtlaZ NSP-Z sensor plate. To identify the ideal frequency, researchers compare the impedance magnitude (|Z|) of a cell-covered electrode to that of a cell-free electrode. By plotting the ratio of these impedances across frequencies, a curve is generated, with the peak indicating the "sweet spot", the most sensitive frequency. This frequency offers the broadest range of relative change in impedance, making it most sensitive for detecting alterations in cell layer properties.