Preparation、characterization And Modification Of PSF Membrane And Its Application On Membrane Type Oxygenator

Artificial lung, also called membrane oxygenator or gas exchange device, is used routinely in cardiopulmonary bypass during open-heart surgey to support life when patient’s lung is failured or traumed. Membrane oxygeantor is designed to take over or supplemet the respiratory function of the natural lung, which is to oxygenate the blood and delivery carbon dioxide produced during the metabolism process. Artificial lung is the most important medical device to treat acute respiratory failure disease and to provide bridge for lung transplant; it also plays a key role in cardiovascular and heart valve replacement operation. Generally, at the core of the artificial lung is polymeric membrane material that separate blood from oxygen. In this paper, polysulfone (PSF) is selected as basement membrane for oxygenator, firstly, the most efficient basement membrane is prepared by optimizated experimental condition; secondly, polyethylene glycol (PEG) and heparin sodium molecule are grafted onto the surface of PSF membrane by chemical modification and low temperature plasma technology to improve biocompatibility of basement membrane; besides, the results of two modification methods are compared to show their adavantages and disadvantages.1. Preparation and optimization of PSF basement membraneIn this study, we investigated concentration of PSF casting solution and pre-volation time of pristine membrane on the effect of PSF membrane performance. To evaluate the efficency of PSF membrane, gas permeation, critical water permeability pressure, mechanical strength, also gas-liquid transport through PSF membrane were all tested. It was demonstrated through experiments of membranes preparation that with increasing PSF concentration of casting solution, permeation flux of O2 and CO2 decreased, while critical water permeability pressure (CWPPM) and mechanical strength of membrane increased. Moreover, prolonging pre-volatilization time of wet membrane had a disadvantage on gas permeation but had little effect on CWPPM. Accordingly, the optimal PSF concentration of casting solution and pre-volatilization time of wet membranes is 15% and 5s, respectively. Besides, application experimental results of gas-liquid transport through PSF membrane oxygenator indicated that when the flow rate of simulation liquid reached 1.5L/min, permeation flux of O2 and CO2 were 8.5ml/min and 364.5ml/min, respectively, which showed that PSF membrane are capatibility of transporting oxygen and carbon dioxide.2. Grafting PEG and heparin sodium on the surface of PSF membrane by chemical modification methodIn the chapter, chlorinated PSF (CMPSF), hydrophilic PSF membrane (PSF-PEG, PSF-PEG-Hep) were prepared from polysulfone membranes covalently conjugated with PEG and heparin sodium to improve biocompatibility of PSF membrane. The immobilized amount of PEG on PSF membranes was controlled by the amount of PEG in the reaction solution and the reaction time. The PSF-PEG membranes were found to be the most proper when weight ratio of PEG and CMPSF is 2 and reaction is 24 hour. By comparison of biocompatibility of graftion different PEG molecule weight on the PSF membrane surface, it was found that PSF-PEG1w-Hep membrane gave the lowest bovine serum albumin adsorption, the smallest blood platelet adhesion and the least thrombus. Besides, application experimental results of gas-liquid transport through PSF -PEGlw-Hep membrane oxygenator indicated that when the flow rate of pig blood reached 1.5L/min, permeation flux of O2 and CO2 were 110ml/min and 102ml/min, respectively, which could achieve the gas exchange transmission capacity of membrane oxygenator.3. Grafting PEG-1w and heparin sodium on the surface of PSF membrane by low temperature plasma modification technologyIn the chapter, we tried to graft PEG-1w onto the surface of PSF membrane and fllowed immbolization of heparin molecule by low temperature plasma technology. Physicial properties, chemical characters and biocompatibility of modified membrane were tested. The results showed that, compared with chemical modification method, plasma modificated PSF membrane maintained much more good performance of PSF basement membrane, especially its CWPPW. Moreover, amout of immbolizated heparin sodium on plasma modificated membrane was more than that of chemical modificated membrane, for plasma treatment could activate much more active free radical on PSF membrane surface. Therefore, plasma irration method enhanced biocompatibility of membrane comparing chemical modification method. Furthmore, PSF-PEGlw-Hep membrane showed better biocompatibility than PSF-Hep membrane, which depicted space resistance of long chain PEG molecule was beneficent for heparin molecule to improve its anticoagulant property.However, these two modification methods had their own merits and defaults. Chemical modification method could immobilize molecule permently through it modificated the basic structure of PSF membrane; plasma modification technology is simple and convenient for operation, maintaining the performance of PSF membrane, but the molecule immbolized by the method is easy to be immsered into blood.