Integrated opto-fluidic device for high-power living cell exposure and detection

Genome editing comprises the most promising work in 21st century genetics, with molecular surgery as its practical horizon. For a successful clinical application of molecular surgery, e.g. to treat cancer, safe and efficient editing is crucial. Light-induced molecular surgery is the perfect tool for its excellent control over wavelength, power, and exposure time. Light is also an excellent tool for the detection of (living) cells. These modalities are ideal for opto-fluidics: combining integrated photonics and microfluidics in a chip. In this work, we used the TriPleX® waveguide platform, comprised of silicon nitride and silicon oxide, to control high power (>1W) visible light. Living cells are inserted into a 100 micrometer wide microfluidic channel after which they are focused into a 25 micrometer wide section in its center using side-, back- and lift sheath flows. The cells can be readily recovered at the microfluidic channel's output with >90% survival rate. Chemically deactivated CRISPR/Cas9 molecules are activated by the laser light for safe molecular surgery. In parallel, it is possible to detect living cells flowing in the microfluidic channel. Measuring light absorption by the analyte makes it possible to detect each individual cell passing by the laser light, and to microscopically verify that >97% of the cells are correctly centered in the microfluidic channel. This device represents a first step to a fully integrated on-chip flow cytometer. Early results demonstrate its efficacy in cell detection and controllable exposure, paving the way to safe molecular surgery.