Surface Localized Coacervation Controlled by Bioactive Nanoarchitectonic Polyelectrolyte Multilayers.

Liquid-liquid phase separation (LLPS) of biomolecules is increasingly studied in bulk conditions mainly because of its expected implication in the emergence of life. However, in living systems, the LLPS occurs also at interfaces through a precise spatiotemporal localization-induction way. Based on enzymatically active nanoarchitectured polyelectrolyte multilayer (PEM) films, a tunable stimuli-responsive surface controlling coacervation processes specifically at the solid-liquid interface is developed. Urease, embedded in multilayers, is used as a trigger to increase locally the pH near the surface in the presence of urea. The deprotonation of a short peptide synthon FFssFF occurs in close vicinity of the surface and induces the formation of FFssFF coacervate droplets at, and in, the vicinity of the surface. The variation of i) the number of enzyme layers in the PEM film, the concentration of ii) urea, or iii) coacervator impacts the kinetic, the size, and the surface density of the droplets which can result in a quasi-full covering of the surface. Based on optical and fluorescence microscopy images using a fluorescently labelled FFssFFK-Bodipy coacervator, a mechanism of the droplet's formation is established explaining the spatial localization and the control of the coacervation process.