Mammalian cells have become the predominant expression system for the production of biopharmaceuticals due to their capabilities in posttranslational modifications. In recent years, the efficacy of these production processes has increased significantly through technical improvements. However, the state of the art in the development of producer cell lines includes many manual steps and is as such very time and cost consuming. In this study we developed a process combination of Raman micro-spectroscopy, laser-induced forward transfer (LIFT) and surface-enhanced Raman spectroscopy (SERS) as an automated machine system for the identification, separation and characterization of single cell-clones for biopharmaceutical production. Raman spectra showed clear differences between individual antibody-producing and non-producing chinese hamster ovary (CHO) cells after their stable transfection with a plasmid coding for an immunoglobulin G (IgG) antibody. Spectra of producing CHO cells exhibited Raman signals characteristic for human IgG. Individual producing CHO cells were successfully separated and transferred into a multiwell plate via LIFT. Besides, changes in concentration of human IgG in solution were detected via SERS. SERS spectra showed the same peak patterns but differed in their peak intensity. Overall, our results show that identification of individual antibody-producing CHO cells via Raman micro-spectroscopy, cell separation via LIFT and determination of changes in concentrations of overexpressed protein via SERS are suitable and versatile tools for assembling a fully automated system for biopharmaceuticals manufacturing.
Keywords: Raman micro-spectroscopy; automated single cell cloning; cell screening; laser-induced forward transfer; surface-enhanced Raman spectroscopy.
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