Real-time characterization of uptake kinetics of glioblastoma vs. astrocytes in 2D cell culture using microelectrode array.

Extracellular measurement of uptake/release kinetics and associated concentration dependencies provides mechanistic insight into the underlying biochemical processes. Due to the recognized importance of preserving the natural diffusion processes within the local microenvironment, measurement approaches which provide uptake rate and local surface concentration of adherent cells in static media are needed. This paper reports a microelectrode array device and a methodology to measure uptake kinetics as a function of cell surface concentration in adherent 2D cell cultures in static fluids. The microelectrode array simultaneously measures local concentrations at five positions near the cell surface in order to map the time-dependent concentration profile which in turn enables determination of surface concentrations and uptake rates, via extrapolation to the cell plane. Hydrogen peroxide uptake by human astrocytes (normal) and glioblastoma multiforme (GBM43, cancer) was quantified for initial concentrations of 20 to 500 µM over time intervals of 4000 s. For both cell types, the overall uptake rate versus surface concentration relationships exhibited non-linear kinetics, well-described by a combination of linear and Michaelis-Menten mechanisms and in agreement with the literature. The GBM43 cells showed a higher uptake rate over the full range of concentrations, primarily due to a larger linear component. Diffusion-reaction models using the non-linear parameters and standard first-order relationships are compared. In comparison to results from typical volumetric measurements, the ability to extract both uptake rate and surface concentration in static media provides kinetic parameters that are better suited for developing reaction-diffusion models to adequately describe behavior in more complex culture/tissue geometries. The results also highlight the need for characterization of the uptake rate over a wider range of cell surface concentrations in order to evaluate the potential therapeutic role of hydrogen peroxide in cancerous cells.