Traditional Single Cell Isolation Techniques for Cell Line Development

Chinese hamster ovary (CHO) cells are widely used in therapeutic antibody production. Generating a clonal cell population is key to making stable cell lines for therapeutic antibody production. A typical cell line development workflow begins with transfection of CHO cells with an immunoglobulin (IgG)-expressing vector of choice. Single, viable CHO cells that have been transfected are then isolated for clonal expansion; high titer clones are screened for stability and productivity. The next step is to expand these high antibody-producing CHO cell lines for large scale antibody production.

A critical step in the cell line development workflow involves the isolation of single, viable cells. Fluorescence-Activated Cell Sorting (FACS) or limiting dilution have traditionally been used to achieve single cell clones although each method has inherent drawbacks. FACS instruments require specialized training, have significant set-up time, and, crucially, require replacement of fluidics lines to ensure no sample-sample cross-contamination occurs. Additionally, FACS utilizes high pressure (up to 70 PSI) which can induce stress and reduce cell viability, especially for difficult to express proteins.

While gentler than FACS sorting, limiting dilution is labor intensive, time consuming, and inefficiently produces single cell clones. These drawbacks highlight the need for more automated, high-throughput solutions.