Engineered Protein Nanosheets for the Scale up of Mesenchymal Stem Cell Culture on Bioemulsions

The rapid progress in cell therapies and stem cell technologies requires the development of novel bioprocessing and biomanufacturing pipelines able to cope with the scale up of cell manufacturing. In this respect, microdroplet technologies have already revolutionised the field of biotechnologies, but remain ill-suited to the culture of adherent cells. In this report, we describe the engineering of albumins with cell adhesive peptides for the stabilisation of microdroplets enabling the scale up of mesenchymal stem cell (MSC) expansion. We characterise the modified albumins prior to study their self-assembly at liquid-liquid interfaces via interfacial shear rheology, and mechanical strengthening through the formation of crosslinked nanosheets. The biofunctionalisation of these protein nanosheets is then characterised by fluorescence microscopy. In turn, the ability of the resulting bioactive microdroplets to promote rapid cell adhesion and expansion is examined and the extensive deposition of matrix associated with such cultures is characterised. The culture of MSCs is then scaled up 100 fold, first at the surface of fluorinated oil emulsions, then on plant-based emulsions stabilised by engineered protein nanosheets and the phenotype of resulting cells is characterised. The microdroplet culture system presented displays attractive advantages over existing technologies, in terms of simplicity of processing, compatibility with regulatory expectations and costs of production, and offers exciting opportunities for translation to cell manufacturing, for cell therapies and cultivated meat applications.