A layer-by-layer self-assembly approach to developing an aquaporin-embedded mixed matrix membrane

Aquaporin (AQP) is a water channel protein in biological membranes that possesses exceptional water selectivity and permeability. The AQP-embedded biomimetic membrane can be potentially used in water purification and pharmaceutical separation. A practical and stable design of AQP-embedded mixed matrix membrane has been revealed in this work using the multilayer polyelectrolyte adsorption method. By encapsulating AQP-incorporated vesicles with positively charged poly-l-lysine molecules, the vesicles could be adsorbed onto polyanion films. AFM and FESEM studies showed that the amount of adsorbed vesicles was proportional to the percentage of charged lipids that was present in the liposomes. The AQP embedded layer-by-layer (LbL) membrane demonstrated a water permeability of 6 L m^-2 h^-1 bar^-1 and MgCl₂ rejection greater than 95%. In comparison with the control LbL membrane without embedding any liposomes, the newly designed mixed matrix membrane improved the water permeability by 60% because of the presence of AQPs. The AQPZ-incorporated membrane was also tested for glutathione separation at various pH levels. The rejection rate of glutathione was greater than 93% at pH values ranging from 4 to 9. Since the LbL approach provides the AQP embedded biomimetic membrane with satisfactory stability and separation performance, it makes the large scale fabrication of AQPZ-incorporated membranes feasible and practical.