Impact of the multiscale viscoelasticity of quasi-2D self-assembled protein networks on stem cell expansion at liquid interfaces

Although not typically thought to sustain cell adhesion and expansion, liquid substrates have recently been shown to support such phenotypes, providing protein nanosheets could be assembled at corresponding liquidliquid interfaces. However, the precise mechanical properties required from such quasi-2D nanoassemblies and how these correlate with molecular structure and nanoscale architecture has remained unclear. In this report, we screen a broad range of surfactants, proteins, oils and cell types and correlate interfacial mechanical properties with stem cell expansion. Correlations suggest an impact of interfacial viscoelasticity on the regulation of such behaviour. We combine interfacial rheology and magnetic tweezer-based interfacial microrheology to characterise the viscoelastic profile of protein nanosheets assembled at liquid-liquid interfaces. Based on neutron reflectometry and transmission electron microscopy data, we propose that the amorphous nanoarchitecture of quasi-2D protein nanosheets controls their multi-scale viscoelasticity which, in turn, correlates with cell expansion. This understanding paves the way for the rational design of protein nanosheets for microdroplet and bioemulsion-based stem cell manufacturing and screening platforms.

Automated summary

Although liquid substrates are not typically believed to support cell adhesion and expansion, recent studies have shown that they can do so by assembling protein nanosheets at liquid-liquid interfaces. However, the mechanical properties required for such quasi-2D nanoassemblies and their correlation with molecular structure and nanoscale architecture are still unclear. In this study, we screened various surfactants, proteins, oils, and cell types, and correlated the interfacial mechanical properties with stem cell expansion. The results suggest that interfacial viscoelasticity has an impact on regulating cell behavior. By using interfacial rheology and magnetic tweezer-based interfacial microrheology, we characterized the viscoelastic profile of protein nanosheets assembled at liquid-liquid interfaces. Based on neutron reflectometry and transmission electron microscopy data, we propose that the amorphous nanoarchitecture of quasi-2D protein nanosheets controls their multi-scale viscoelasticity, which correlates with cell expansion. This understanding provides insights for the rational design of protein nanosheets for stem cell manufacturing and screening platforms based on microdroplets and bioemulsions.