Separating Extreme pH Gradients Using Amphiphilic Copolymer Membranes.

Polymeric vesicles, also called polymersomes, are highly efficient biomimetic systems. They can generate compartmentalized volumes at the nanoscale supported by synthetic amphiphilic membranes that closely mimic their biological counterparts. Membrane permeability and the ability to separate extreme pH gradients is a crucial condition a successful biomimetic system must meet. We show that polymersomes formed by non-ionic polybutadiene-b-polyethylene oxide (PBd-b-PEO) amphiphilic block copolymers engineer robust and stable membranes that are able to sustain pH gradients of 10 for a minimum of eight days. The cells' endo-lysomal compartments separate gradients between three and one, while we generated a pH gradient of threefold as great. This feature clearly is of great importance for applications as nanoreactors and drug-delivery systems where separating different aqueous volumes at the nanoscale level is an essential requirement.