Capacitance-based assay for real-time monitoring of endocytosis and cell viability

Abstract

Label-free cell-based assays have emerged as a promising means for high-throughput screening. Most label-free sensors are based on impedance measurements that reflect the passive electrical properties of cells. Here we introduce a capacitance-based assay that measures the dielectric constant (capacitance) of biological cells, and demonstrate the feasibility of analyzing endocytosis and screening chemotherapeutic agents with this assay. Endocytosis induces a change in the zeta potential, leading to a change in the dielectric constant which enables real-time endocytosis monitoring using the capacitance sensor. Additionally, since the dielectric constant is proportional to cell radius and cell volume, cell viability can be estimated from the change in capacitance. Therefore, the capacitance sensor array can also be used for cytotoxicity testing for large-scale chemotherapeutic screening.

Real-Time Discrimination between Proliferation and Neuronal and Astroglial Differentiation of Human Neural Stem Cells

“…Under proliferation conditions in PM, the capacitance increased steadily due to increases in cell size and number (Supplementary Fig. S4) and became nearly constant after ~4.5 days, as previously reported14151617. When the cells grew under differentiation conditions, the capacitance also increased, but the rate of increase was much slower than that of the cells grown under proliferation conditions (Supplementary Figs.…”

“…Cells attach and spread on the surface of the sensing electrode and passively block the current, and thus the electrode impedance is affected by the shape, adhesion, and/or mobility of adherent cells1213. However, compared to the electrode impedance, the capacitance (or the dielectric constant) of cells provides more direct information on cellular activities14151617; the fate potential of NSCs was previously reported to be more closely related to cell membrane capacitance than to conductance18. On this study, we have developed a capacitance sensor to monitor the differentiation of hNSCs.…”

Real-time estimation of paracellular permeability of cerebral endothelial cells by capacitance sensor array

“…1 ). In our system, cells were plated between gold electrodes and the change in dielectric constant (ε) is measured to estimate the capacitance ( C ) with an equation C = ε A / d , where A is the electrode area and d is the distance between the two electrodes 12 13 14 15 . To increase paracellular permeability of cerebral endothelial cells, we treated endothelial cells in monolayer with VEGF (20 ng/mL), which is known to increase cerebral vascular permeability, 16 17 after 24 hours of stabilization.…”

“…With interdigitated electrodes, capacitance values were obtained from cells between electrodes in a relationship of C = ε A / d without additional manual electrodes in conventional ECIS system. Interestingly, dielectric spectroscopy is a useful tool to monitor cellular events such as cell death, cell differentiation, and endocytosis 10 12 13 14 15 . In line with these studies, we showed that capacitance measurement could also be utilized in monitoring paracellular permeability of cerebral endothelial cell monolayer.…”

“…The capacitance (or dielectric constant) could be also a potential candidate to estimate the changes in the integrity of cerebral microvasculature. This method is a useful way to obtain real-time electrical properties such as cell membrane capacitance and cytoplasm conductivity 10 Upon application of AC electrical fields, cells demonstrate specific dielectric responses according to interfacial polarization patterns 11 Interestingly, recent studies have demonstrated that this technique can be utilized to observe various cellular functions including cell viability/death, endocytosis, and differentiation 10 12 13 14 15 In the similar manner, we speculated that we could differentiate the status of paracellular permeability of cerebral microvascular endothelial cell monolayer with the capacitance sensor array.…”