Combined optical coherence phase microscopy and impedance sensing measurements of differentiating adipose derived stem cells

There is a growing interest in monitoring differentiating stem cells in 2D culture without the use of labelling agents. In this study we explore the feasibility of a multimodality method that combines impedance sensing (IS) and optical coherence phase microscopy (OCPM) to monitor the main biological events associated with adipose derived stem cells differentiation into different lineages. Adipose derived stem cells were cultured in Mesenpro RS medium on gold electrode arrays. The system (ECIS, Applied biophysics) is connected to a lock-in amplifier controlled by a computer, and the complex impedance is derived from the in phase and out of phase voltages. Multi-frequency measurements spanning from 500Hz to 100 kHz are recorded every 2 minutes. The Optical coherence phase microscope is build around a Thorlabs engine (930nm FWHM: 90nm) and connected to a custom build microscope probe. The IS and OCPM were successfully integrated. The electrode area (250um) was imaged with a lateral resolution of 1.5um during impedance measurements. Impedance sensing gave an average measurement of differentiation, as a change in impedance over the electrode area, whereas OCPM provides additional information on the cellular events occurring on top of the electrode. The information retrieved from OCPM will feed a mathematical model correlating cellular differentiation and impedance variation. In this study we have demonstrated the feasibility of integrating two non-invasive monitoring techniques that will be instrumental in designing stem cell based screening assays.