Real time monitoring of the cell viability during treatment with tumor-targeted toxins and saponins using impedance measurement.

This work describes the application of an impedance-based measurement for the real time evaluation of targeted tumor therapies in cell culture (HeLa cells). We used a treatment procedure that is well established in cells and mice. Therein, tumor cells are treated with a combination of an epidermal growth factor-based targeted toxin named SE and particular plant glycosides called saponins. In the present study HeLa cells were seeded in different numbers onto interdigitated electrode structures integrated into the bottom of a 96 well plate. The cells were treated with SE in the presence and absence of the saponin SpnS-1 (isolated from Saponaria officinalis roots). The impedance was directly correlated with the viability of the cells. As expected from known end point measurements, a concentration dependent enhancement of toxicity was observed; however, with the impedance measurement we were for the first time able to trace the temporal changes of cell death during the combination treatment. This substantially added to the understanding of initial cellular mechanisms in the augmentation of the toxicity of targeted toxins by saponins and indicated the superiority of real time monitoring over end point assays. The method is less labor intensive and label-free with ease of monitoring the effects at each time point.