Following transfection, single cells need to be isolated from transfected pools. Traditionally, this crucial step has been performed by limiting dilution. Based on early regulatory guidelines released by the U.S. Food and Drug Administration (FDA) and others, the production cell line of recombinant products is to be derived from a single cell in order to minimize population heterogeneity as well as facilitate isolation and subsequent selection of high-producing clones.

After single-cell cloning, clones exceeding a certain confluency threshold are selected for suspension culture in order to expand cell numbers. Traditional workflows for cell culture happen under static conditions, taking up several weeks of work before viable clones are transferred to shaken deep well or 24-well plates. After additional cultivation, selected clones are then transferred to larger volumes and finally to shake flasks or mini bioreactors. Hence, during the first weeks after cloning, cells are cultured under static conditions, which do not match the culture environment the cells experience in later stages of the process and during production. Our innovative microbioreactor platform, the S.NEST™, was developed to enable suspension culture early in the CLD process. With the S.NEST platform, cells are kept in a more suitable environment thanks to the circulating flow of medium, thus maintaining homogenous levels of nutrients and dissolved oxygen.