SINOPSIS

The existing methods for detection of neural activity during optogenetic stimulation are either mechanically intrusive or chemically invasive. Here, we report development of a label-free non-invasive optical readout method to monitor the changes in the cells resulting from optogenetic activation. Phase sensitive Fourier domain optical coherence tomography (PSFD-OCT) was deployed to detect the activation of Channelrhodpsin-2 sensitized cells under the stimulation of blue light. A monolayer of transfected human embryonic kidney cells (HEK 293) in a cell culture dish was activated using a fiber-coupled laser diode that was modulated by a square wave (frequency 30Hz with 50% duty cycle). Using the PSFD-OCT system, we demonstrate measurement of the optical path length change in the cell monolayer because of light-induced activation.