Biomimetic cell structures: Probing Induced pH-Feedback Loops and pH Self-Monitoring in Cytosol Using Binary Enzyme-loaded Polymersomes in Proteinosome

Structures and functions of eukaryotic cells with an outer permeable membrane, motility, a cytoskeleton, biomolecules diffusion, and functional organelles can be imitated by a multi-compartmentalized and large-sized protocell containing various synthetic organelles. Herein, two kinds of artificial organelles with stimuli-trigged regulation ability, glucose oxidase-(GOx)-loaded pH-responsive polymersomes A (GOx-Psomes A) and urease-loaded pH-responsive polymersomes B (Urease-Psomes B) for probing biomimetic pH homeostasis, and a pH-sensor (Dextran-FITC) are encapsulated into proteinosomes by Pickering emulsion method. Thus, the polymersomes-in-proteinosome system is realized. Alternating input-regulation of fuels (glucose or urea) outside the protocell penetrates the membrane of proteinosomes and enters into GOx-Psomes A and Urease-Psomes B to produce chemical\biological signals (gluconic acid or ammonia) resulting in pH-feedback loops (pH jump and pH drop). This will counteract the catalytic “switch on” or “switch off” of enzyme-loaded Psomes A and B owing to their different pH-responsive membranes. Thus, the Dextran-FITC promotes a controlled cytosolic spatial organization and the detection of slight pH fluctuations in the lumen of protocells. Overall, this approach shows heterogeneous polymersome-in-proteinosome architectures with sophisticated features such as induced input-regulated pH changes mediated by negative/positive feedback in loops and cytosolic pH self-monitoring, requirements strictly needed in an advanced protocell design.