Planar biomimetic aquaporin-incorporated triblock copolymer membranes on porous alumina supports for nanofiltration

The aim of the present study was to investigate and demonstrate the preparation and characterization of planar biomimetic water-channel protein Aquaporin Z (AqpZ)-incorporated polymer membranes on different porous alumina substrates by vesicle spreading. AqpZ-incorporated polymer vesicles were prepared from disulfide-functionalized poly(2-methyloxazoline)-block-poly(dimethylsiloxane)-block-poly(2-methyloxazoline) (disulfide-functionalized PMOXA 20 -PDMS 75 -PMOXA 20 ) tri-block copolymer which was previously proven to be able to maintain protein activity after the incorporation as found in lipid vesicles. AqpZ-incorporated vesicle permeability was evaluated using stopped-flow spectroscopy. The permeability of AqpZ-vesicles measured by stopped-flow spectroscopy was 4680 μm/s at room temperature when the molar ratio of AqpZ/polymer used to prepare the vesicles was 1/50. The result demonstrates that AqpZ could maintain its performance after inserting into polymer vesicles. In addition, the vesicles were designed with disulfide functional end groups to enhance vesicle spreading on gold-coated solid substrates by covalent interactions between polymer membranes and substrates. The morphology of polymer membranes on different types of porous alumina substrates was elucidated by using atomic force microscopy (AFM) and field-emission scanning electron microscopy (FESEM). AqpZ-incorporated polymer vesicles were demonstrated to be able to form planar AqpZ-incorporated polymer membranes on the porous alumina substrates. Preliminary studies of membrane's permeability showed that AqpZ were still in the active form on the planar membranes and the resultant membranes may be useful tools for nanofiltration process for water reuse.