Strong Elastic Protein Nanosheets Enable the Culture and Differentiation of Induced Pluripotent Stem Cells on Microdroplets

Advances in stem cell technologies, revolutionising regenerative therapies and advanced in vitro testing, require novel cell manufacturing pipelines able to cope with scale up and parallelisation. Microdroplet technologies, which have transformed single cell sequencing and other cell-based assays, are attractive in this context, but the inherent soft mechanics of liquid-liquid interfaces is typically thought to be incompatible with the expansion of induced pluripotent stem cells (iPSCs), and their differentiation. In this work, we report the design of protein nanosheets stabilising liquid-liquid interfaces and enabling the adhesion, expansion and retention of stemness by iPSCs. We use microdroplet microfluidic chips to control the formulation of droplets with defined dimensions and size distributions and demonstrate that these sustain high expansion rates, with excellent retention of stem cell marker expression. We further demonstrate that iPSCs cultured in such conditions retain the capacity to differentiate into cardiomyocytes and demonstrate such process on droplets. This work provides clear evidence that local nanoscale mechanics, associated with interfacial viscoelasticity, provides strong cues able to regulate and maintain pluripotency, as well as to support commitment in defined differentiation conditions. Microdroplet technologies appear as attractive candidates to transform cell manufacturing pipelines, bypassing significant hurdles paused by solid substrates and microcarriers.