Liquid–liquid phase separation (LLPS) is an emerging and universal mechanism for intracellular organization, particularly, by forming membraneless organelles (MLOs) hosting intrinsically disordered proteins (IDPs) as scaffolds. Genetic engineering is generally applied to reconstruct IDPs harboring over 100 amino acid residues. Here, we report the first design of synthetic hybrids consisting of short oligopeptides of fewer than 10 residues as “stickers” and dextran as a “spacer” to recapitulate the characteristics of IDPs, as exemplified by the multivalent FUS protein. Hybrids undergo LLPS into micron-sized liquid droplets resembling LLPS in vitro and in living cells. Moreover, the droplets formed are capable of recruiting proteins and RNAs and providing a favorable environment for a biochemical reaction with highly enriched components, thereby mimicking the function of natural MLOs. This simple yet versatile model system can help elucidate the molecular interactions implicated in MLOs and pave ways to a new type of biomimetic materials.

Peptidic ‘nanomillipede’, consisting of worm-like nanoscale ‘body’ and cysteine-terminated ‘legs’, was synthesized, tuned (with ultrasound) and utilized to crosslink the vinyl sulfone-modified dextran to form hybrid hydrogels with soft-tissue mimicking tuneable mechanical strength, self-healing property, and tuneable shear-thinning property, thereby indicating their potential use in tissue engineering and drug delivery.