The CHO cell line has been widely used for the production of therapeutic proteins. In a typical cell line development workflow, CHO cells are transfected with an IgG expressing vector. A single CHO cell is obtained by limited dilution cloning. A high titer clone is selected using ELISA. Limiting dilution is unreliable and many wells are either empty or have multiple cells. This process of selecting high titer clones is extremely inefficient and costly.