The field of optogenetics is a relatively young discipline in the research field of biology investigating possibilities to remotely control genetically modified cells with visible light. This is achieved by the reversible control of isolated signalling components. Optogenetic proteins have the property to change their conformation and affinity upon illumination with light of a specific wavelength. This process is referred to as photoswitching. Genetic fusion of optogenetic proteins to signalling components allows for the reversible optical control of virtually any signalling pathway. Originating from the field of neurobiology, fluorescence microscopy is the most commonly used analytical method for optogenetic research. Using a confocal fluorescence microscope, small areas of e.g. neuronal membrane can be optically activated to observe synaptic transmission.

An equally powerful method is flow cytometry. Yet, it has hardly been used for optogenetic research. This can be explained by the lack of suitable illumination devices. Currently, the only commercially available procedure is to hold flashlight devices near the reaction tube. Using flashlight devices, the illumination of cell populations is non-homogeneous and not reproducible within or between experiments. The procedure of holding flashlights to the tube while adding stimuli to the cell sample as well as changing the wavelength are tedious, time consuming and prone to error. This also limits the number of wavelengths for one experiment. Opto Biolabs has developed a product, which allows users to analyse optogenetic experiments in a flow cytometer for the first time. The proof of concept for this technology could experimentally be shown at the University of Freiburg.

The aim of the proposed project OptoCS is to develop an illumination device which enables the combination of fluorescence-activated cell sorting (FACS) with optogenetics. It will bridge the gap between basic research and therapeutic applications. Cell sorting is a standard method in individualised immuno-cancer therapy, but not yet feasible for the sorting of optogenetic cell samples. We believe that optogenetic cell sorting will be pivotal for the development of optogenetic therapies. Furthermore, OptoCS will test the functionality of optogenetic cell sorting using established optogenetic tools generated at the University of Freiburg and EMBL as well as in scientific collaborations. Here, different illumination protocols for different optogenetic tools and cell types will be gathered and integrated as standardised illumination protocols into the software of the developed illumination device. This will greatly enhance the exchange and standardisation of optogenetic experimental procedures.