This kit uses sandwich ELISA to determine the concentration of Cas9 in the test sample. The capture Cas9 monoclonal antibody is pre-coated on a 96-well plate. Cas9 standard or test sample is added to the pre-coated plate and will specifically bind to the capture antibody. The biotinylated detection antibody is then added to bind the immune complex, followed by the addition of streptavidin HRP conjugate to form the antibody-antigen-detection antibody-HRP complex. Extra detection antibody and HRP conjugate will be washed off. The addition of TMB results in color changes and the amplitude of the color change is proportional to the amount of Cas9 that specifically binds to the plate. The reaction is stopped with the addition of stop solution and the absorbance is measured at 450nm. The sample Cas9 concentration is calculated from the Cas9 standards titration curve.