Primary cell challenges

While use of primary cells in the drug discovery process has clear advantages, their use presents challenges that have slowed their broader implementation in assays of other types. Typically, special requirements of assays that cannot be adequately addressed by transformed cells have served as the driving force behind the use of primary cells in assays. Among other considerations, in most instances primary cells are more expensive to acquire and use than comparable cell lines. 

The first challenge to the use of primary cells is identifying a primary cell type that is more relevant to the disease or condition under study than existing cell lines. This requires a thorough understanding of the disease and the tissues involved. Not all diseases can be adequately modeled at the cellular level and for those that can be primary cells are not always available in sufficient quantities. 

To begin, enzyme products can be inside the cell (intracellular), loosely associated with the cell, or secreted (extracellular). Each of these products requires a different approach on how to purify the enzyme. The majority of presently commercialized detergent enzymes is of the extracellular variety and can be recovered directly from the fermentation broth. Thus, the primary recovery challenge involves removing the cells from the broth, aptly called cell separation. Three different techniques are commonly used to achieve this goal filtration, microfiltration, and centrifugation. 

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