Abstract:
Controlled design of giant unilamellar vesicles under defined conditions has vast applications in the field of membrane and synthetic biology. Here, we bio-engineer bacterial-membrane mimicking models of controlled size under defined salt conditions over a range of pH. A complex bacterial lipid extract is used for construction of physiologically relevant Gram-negative membrane mimicking vesicles whereas a ternary mixture of charged lipids (DOPG, cardiolipin and lysyl-PG) is used for building Gram-positive bacterial-membrane vesicles. Furthermore, we construct stable multi-compartment biomimicking vesicles using the gel-assisted swelling method. Importantly, we validate the bio-application of the bacterial vesicle models by quantifying diffusion of chemically synthetic amphoteric antibiotics. The transport rate is pH-responsive and depends on the lipid composition, based on which a permeation model is proposed. The permeability properties of antimicrobial peptides reveal pH dependent pore-forming activity in the model vesicles. Finally, we demonstrate the functionality of the vesicles by quantifying the uptake of membrane-impermeable molecules facilitated by embedded pore-forming proteins. We suggest that the bacterial vesicle models developed here can be used to understand fundamental biological processes like the peptide assembly mechanism or bacterial cell division and will have a multitude of applications in the bottom-up assembly of a protocell.
