Small molecule, biotherapeutic, and vaccine development activities frequently require the expression of a variety of proteins ranging from simple recombinant proteins to more complex antibodies, antibody-like molecules, and virus-like particles (VLPs). Stable cell lines have been the standard for protein production for over two decades; however, their creation is a costly, time consuming, and labor-intensive process and may not be possible for all applications. In response, researchers have looked to transient gene expression (TGE) as a means of more rapid, cost-effective protein production, particularly during early development and preclinical stages (1). While TGE generally offers a means of more rapidly expressing proteins, not all transient expression methods meet the requirements for larger scale, gram-level protein production needed throughout the development pipeline.
Transient transfection technologies have evolved from simple chemical carriers such as DEAE-dextran, calcium phosphate, and PEI into sophisticated, highly engineered methodologies such as lipid-based reagents, viral-mediated delivery, and electroporation. These newer transfection methods generally provide enhanced performance and broader applicability when compared to earlier methods, allowing for transfection of mammalian cells, a more difficult subset of cells to transfect, but of high interest during biotherapeutic and vaccine development. Key factors to consider when choosing a transient, protein production system range from cell viability, transfection efficiency, and reproducibility to more practical considerations including ease of use, system flexibility, and resource requirements, as well as the overall cost- effectiveness of the system.
Chemical carriers, while affordable, are prone to high levels of variability and lower expression levels even when using optimized protocols. In contrast, lipid-mediated transfection, virus delivery, and electroporation are more reproducible but differ significantly in scalability, time requirements, and cost. Second generation lipid-based technologies have relatively high transfection efficiencies and the ability to transfect a range of cells, but require re-optimization during scale-up and can become cost prohibitive. Viral delivery methods are scalable and can achieve high levels of transfection efficiency, however, the creation of viral vectors and production of viral stocks require a high level of user knowledge, are labor and time intensive, have limited cell type flexibility, and can impact yield due to purification challenges. MaxCyte’s proprietary flow electroporation technology is a universal transient transfection platform that provides a practical solution to the time, labor, and cost challenges of stable cell lines while overcoming the limitations associated with other transient transfection methods.