Nanoparticle-Based Membranes on Coacervates: From Interfacial Assembly to Biomimetic Applications

Coacervates formed by liquid-liquid phase separation have become important cell-like models for building protocells and simulating intracellular microenvironments. However, the dynamic instability and functional constraints of their membraneless structures have significantly limited the applications of these systems in mimicking complex cell life. One effective method to stabilize, control, and potentially alter their functions is to cover the coacervates with membranes constructed from nanoparticles. Here, we first introduce the formation mechanisms and fundamental physicochemical properties of coacervates. Subsequently, taking the main driving forces of membrane formation (interfacial energy-driven self-assembly, assembly dominated by electrostatic interactions, and synergistic multi-mechanism assembly) as the logical framework, we classify and discuss a selection of exemplary studies. We highlight that the nanoparticle-based membranes significantly improve the structural integrity and the selective molecular permeability of coacervates. These properties enable the realization of biomimetic functions, such as simulating cell metabolism, phagocytosis, motility and signal transduction. Last but not least, we discuss the current limitations in the design and regulation of nanoparticle-coated coacervate microdroplets and propose possible future development directions. This review aims to promote further research and application of coacervates in the fields of synthetic biology and biomimetic materials by outlining the research progress of nanoparticle-based membrane-coated coacervates.