Characterization of aquaporin Z-incorporated proteoliposomes with QCM-D

Aquaporins have high water permeability and selectivity, which make them attractive to use in membrane applications for water purification and desalination. Due to their hydrophobic nature, they have to be embedded in cell membrane-like structures such as liposomes to form proteoliposomes. In this study, the effects of aquaporin Z (AqpZ) addition on liposome characteristics and behavior were investigated by evaluating the adsorption of proteoliposomes onto gold as reference substrate, polysulfone (PS) and polyacrylonitrile (PAN) spin-coated sensor surface as common nanofiltration membrane material by quartz crystal microbalance with dissipation. AqpZ incorporation into liposomes did not significantly change mean liposome diameter and surface charge, but the water permeability was increased up to almost sixfold. The results of viscoelastic modeling showed a stiffer membrane structure for the lipid bilayer of proteoliposomes compared to that of liposomes. Although liposomes and proteoliposomes were found to be adsorbed successfully on negatively charged PS and neutral PAN surfaces, the interaction strength and adsorption rate were found to be different for polymers with different surface properties, indicating the importance of the polymer for the stabilization of proteoliposomes. Findings of this study offer valuable information about the incorporation of proteoliposomes in membrane structures for the fabrication of nanofiltration membranes.