Engineering guidelines for CRISPR diagnostics

Abstract

This Feature Article reviews engineering guidelines for the design of CRISPR assays, including experimentally validated theoretical models and recommendations for experimental research practice and reporting. First, the state of the art of CRISPR kinetics studies is reviewed. Then presented is a summary of the existence and persistence of widespread gross errors in reports of kinetic rate constants of CRISPR-Cas enzymes, as well as the fact that many CRISPR studies provide insufficient data to check for consistency or assess calibration. Proper experimental procedures including signal calibration are critical to the assessment, design, and future development of CRISPR kinetics assays and CRISPR diagnostics. This review then presents guidelines for the calibration of fluorescence-based CRISPR assays. Fluorescence is the most common detection modality, and incorrect calibration is implicated in high-profile, gross errors in the field. Also presented is a review of enzymatic kinetic rates and reporter molecule degradation as the major factor limiting CRISPR assay sensitivity. Lastly, progress in, and criticism of, microfluidic applications of CRISPR assays is summarized.