Abstract
Dielectrophoresis (DEP), the induced motion of cells in an inhomogeneous electric field, can be measured by studying the motion of the cells at different frequencies. This work uses a light absorption method to determine the DEP force and extract the dielectric properties of cell populations. Previously, light intensity changes in a 3D well electrode have been measured with a microscope and a single channel signal generator. This work sets out to enable real time measurement of cell populations by implementing a digital camera, lens and light source alongside a 20 channel signal generator in one machine, the DEP well instrument, to measure light intensity changes for 20 wells simultaneously. Optimisation of the optics is carried out through the evaluation of different cameras, lenses and light sources and measuring the light intensity changes of yeast populations in 4 wells that are energized with the same frequency, in order to ensure that the system is able to give consistent results. Finally, the application of the DEP well instrument for detection of drug cytotoxicity and rapid detection of apoptosis, both important in the development of new chemotherapeutic drugs, was studied. Both apoptosis and cytotoxicity of drugs can be characterized by changes in the membrane and cytoplasm properties of cells resulting in various distinct sub-populations within a sample. Rapid detection of apoptosis was examined by inducing HeLa cells with the well known chemotherapeutic agent staurosporine and comparing the results obtained with DEP and those obtained with the gold standard method of measuring apoptosis, Annexin V assay with flow cytometry. The ability of the DEP well instrument to test drug cytotoxicity on suspension and adherent cells was studied by inducing cells with the chemotherapeutic agent doxorubicin and measuring cell viability with DEP after different incubation times. The results were compared with the colorimetric assay 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) and trypan blue experimental results, as well as with previously published values.