Intercellular Instructed-Assembly Mimics Protein Dynamics To Induce Cell Spheroids.

Cell-mediated remodeling of extracellular matrix (ECM) plays important roles for cell functions, but it is challenging to develop synthetic materials for mimicking such a dynamic aspect of proteins in ECM. Here we show that intercellular morphological transition of peptide assemblies mimic the unfolding of fibronectin, thus enabling formation of spheroids from a monolayer of cells. Specifically, the phosphopeptide self-assembles to form nanoparticles, which turns into nanofibers upon partial dephosphorylation catalyzed by enzymes (e.g., phosphatases) at intercellular space. Occurring between HS-5 cells, such an enzyme-instructed self-assembly enables a sheet of the HS-5 cells to form cell spheroids. Structure-activity investigation reveals that proteolytic stability, dephosphorylation, and biotin conjugation of the peptides are indispensable for forming the cell spheroids. Further mechanism study indicates that the intercellular assemblies interact with multiple ECM components (e.g., laminin, collagens III and IV) to drive the formation of the cell spheroids. As the first example of intercellular instructed-assembly from homotypic precursors, this work illustrates a new approach that uses cell-responsive peptide assemblies to mimic protein dynamics for control cell behaviors.