Abstract
Cell spheroids, including organoids, serve as a valuable bridge between in vitro systems and in vivo animal models, offering powerful tools for studying cell biology in a three-dimensional environment. However, existing methods for generating cell spheroids are time-consuming or difficult to scale up for large-scale production. Our recent study has revealed that transcytotic peptide assemblies, which transform from nanoparticles to nanofibers by enzymatic reactions, can create an intercellular fibrils/gel, accelerating cell spheroid formation from 2D cell culture or cell suspension. While this finding presents an alternative approach for generating cell spheroids, the specific structural features required for efficient cell spheroids formation remains unclear. Based on our observation that a phospho-tetrapeptide with a biphenyl cap at its N-terminus enables cell spheroid formation, we produced 10 variants of the original peptide. The variants explored modifications to the peptide backbone, length, electronic properties of the biphenyl capping group, and the type of phosphorylated amino acid residue. We then evaluated their ability for inducing cell spheroid formation. Our analysis revealed that, among the tested molecules, peptides with C-terminal phosphotyrosine, low critical micelle concentration, and dephosphorylation-guided nanoparticle to nanofiber morphological transition were the most effective in inducing the formation of cell spheroids. This work represents the first example to correlate thermodynamic properties (e.g., self-assembling ability) and kinetic behavior (e.g., enzymatic dephosphorylation) of peptides with the efficacy of controlling intercellular interaction, thus offering valuable insights for using enzymatic self-assembly to generate peptide assemblies for biological applications.