Design And Fabrication Of The Aquaporin Incorporated Phospholipid Composite Membranes

Seawater desalination is one of the effective ways to solve the shortage of waterresources, while the membrane separation technology is the most efficient andeconomical way to realize seawater desalination. The design of high performancemembrane is the foundation and core of membrane technology. We currently reach aconsensus that preparing new composite membrane can reduce energy consumptioneffectively and achieve efficient and convenient water purification technology. It isalso the direction of future development in membrane material research field. Theaquaporin, which has extremely strong water permeability and single-choicepermeability, is an ideal channel of water molecules. Formed through wrapping waterchannel proteins in the membrane of the bilayer and spreading in nanofiltrationmembrane, the new type of bionic composite membrane is able to overcome thetraditional polymer composite membrane’s "trade-off effect". The essay presents themethod of preparing for the bionic composite phospholipid membranes withaquaporin, which unites vesicle fusion with covalent bond combination. Furthermore,the membrane’s structure and performance are also characterized and tested.This essay uses many methods, such as atomic force microscope (AFM)characterization, confocal laser scanning microscope (CLSM) characterization,attenuated total internal reflectance fourier transform Infrared spectroscopy(ATR-FTIR) characterization and so on, to check the effect of many factors onmaking preparation for double-layer phosholipid membranes by using vesicle fusion,mainly including deposition time, deposition temperature, vesicle concentration andmonoolein (MO) content. Through characterizing contact angle, water flux and saltrejection, we also evaluate the performance of phospholipid complex membranesmade by the way of vesicle fusion.(1) Through the characterization toward appearance of AFM and CLSM, the fourphospholipids including DPPC, MO/DPPC, DOPC, MO/DOPC can all form phospholipid bilayer membranes on the membrane surface of NTR-7450and NF-270by the means of vesicle fusion. The perfect condition for the membrane formation isspreading out for2h under25℃, with the vesicle density at0.05mg/ml and theaddition of MO mol ratio at0.5. At room temperature, the phospholipid bilayermembrane formed by DOPC has better quality than that formed by DPPC. AddingMO can lower the temperature of mutual transformation of DPPC system andimprove the quality of the membrane that it forms at room temperature. Whereasadding MO to DOPC system will lower the quality of the membrane that it formed;adding excess MO will have bad influence on the membranes of DOPC and DPPC.The surface of NTR-7450membrane is less rough, which makes it more conducive tothe formation of high-quality phospholipid bilayer membrane than NF-270.Meanwhile, the phospholipid bilayer membranes formed on NTR-7450have keptbetter mobility, which is conductive to maintain the activity of aquaporin.(2) For composite membrane phospholipids containing water channel proteinmade through vesicle fusion method, water flux and salt rejection of the phospholipidcomposite membrane will also be enlarged with the increase of the content of AQP1;but the aquaporin itself has negative charges, which hinder the introduction ofsubsequent protein. Meanwhile, the quantity of aquaporin that each vesicle carries islimited, so the change of flux and the quantity of protein is not a linear relation.High-quality phospholipid bilayer is conductive to the exertion of aquaporin’sfunction.This study also used dopamine (DOPA) to change the polysulfone (PS)membrane ultrafiltration membrane and NF-270, to obtain DOPA composite layercontaining carboxyl groups, to generate the amide bond with1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) through the catalyticreaction with1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC) and sulfoneN-hydroxysuccinimide (S-NHS), thus to prepare composite membrane phospholipidswith the combination of covalent bond, and carry on the inspection of scanningelectron microscope (SEM) characterization, ATR-FTIR characterization, contactangle, water flux and salt rejection. Through researches, it is found that the DOPE bilayer phospholipid membrane formed on the modification base greatly increases thehydrophilicity of the membrane. In the ATR-FTIR test, it is established that DOPAlayer and DOPE phospholipid bilayer indeed conduct amidation reaction throughobserving carbonyl group at1640cm-1and character peak of P-O-C at1068cm-1,which illustrate that the preparation of composite phospholipid membrane withcovalent bond combination is successful. Proper porogen content is a vital influencingfactor for the preparation of infiltrative supporting seat of phospholipid biomimiccomlex membranes. After introducing AQP1, the flux and salt rejection ofphospholipid biomimic composite membranes consisted of covalent bondcombination spontaneously increase. It proves that the introduction of AQP1to theconposite membrane is successful, and that the hypothesis concerning the preparationof biomimic composite membranes consisted of covalent bond combination isachievable.