Microfluidic tool for rapid functional characterization of CRISPR complexes

RNA guided nucleases are regarded as the future genome editing technologies. As such, they need to meet strong safety margins. Two major challenges in incorporating CRISPR technologies into the clinical world are off-target activity and editing efficiency. The common way to tackle such issues is to measure the binding and cleavage kinetics of the CRISPR enzyme. This can be challenging since, for example, DNA is not released from the CAS9 protein post cleavage. Here a promising new microfluidic approach to characterizing Enzymatic Interaction and Function of CRISPR complexes on a microfluidic platform (EnzyMIF) is presented. The method can rapidly detect the k_d, k_off, k_m and k_cat for various RNA guided nucleases. In this work, two single guide RNAs with significantly different in-cell cleavage efficiency, RAG2 and RAG1, are used as proof-of-concept. The EnzyMIF assay results provide biochemical characterization of these guide RNAs that can explain the difference in cleavage using both wild type (WT) CAS9 and HiFi CAS9. Notably, it is shown that EnzyMIF characterization correlates with cell culture genomic editing efficiency results. It is suggested that EnzyMIF can predict the quality of cleavage rapidly and quantitatively.