pH-Driven Compartmentalization in Coacervate Protocells Enables Programmable Microreactors

Bottom-up construction of artificial cells is pivotal for investigating the functional and structural evolution of protocell systems. Here, a streamlined methodology is reported for constructing a protocell model that exhibits pH-adaptive responsiveness and functions as an efficient microreactor for cascade biochemical reactions. These protocells are engineered through liquid-liquid phase separation (LLPS) of poly(diallyldimethylammonium chloride) (PDDA) and adenosine triphosphate (ATP), yielding coacervate microdroplets that serve as nucleation sites for spontaneous self-assembly of phospholipid semipermeable membranes. By tuning the pH environment of the membranized protocells, the hydrolytic property of ATP under acidic conditions modulates the surface charge density of coacervates, triggering elevated surface potential and altered interfacial tension, which ultimately induce secondary phase separation inside the protocells to yield dynamically reconfigurable microcompartments. Notably, introduction of small-molecule substrates triggers enzymatic reactions within the molecularly crowded lumen of the protocells, which in turn drives pH-mediated micro-compartmentalization, enabling the coupling of biocatalysis with structural dynamics. This protocell model, characterized by programmable dynamic micro-compartmentalization, offers distinct advantages for applications in cellular mimicry, synthetic protobiology, and the development of artificial biomolecular microreactors.