Study On Grafting Multi-Fluoro Molecules Onto The Surface Of Poly-4-Methyl-1-Pentene Hollow Fiber Membranes For Artificial Lungs

Artificial lung,also known as extracorporeal membrane oxygenator,or extracorporeal gas exchange device,is commonly used as backup for respiratory system in conditions of open heart surgery and respiratory failure.In application patients'venous blood is bumped through vessels in the main chamber,where gas exchanges happens.The CO2 in the blood was expelled and the O2 was embraced,after which the blood was transferred back to patients' bodies.From 20th century the military conflicts became more common worldwide,which resulted in the growing number of wounds in urgent need for transfusion therapy.In the meantime the patients getting trouble in respiratory system and blood circulation system kept increasing.It is predicted that the need for transfused blood will rise over 10%,which has great gap with the lack in blood supply.Therefore the substitutes for natural blood are gradually developed,which are called artificial blood.The artificial blood includes two main types:the hemoglobin-based oxygen carriers and the perfluorocarbon-based oxygen carriers.The later type mainly utilize the considerable dissolving capacity for oxygen of perfluorocarbon.Our group has a study history of polymer materials used for artificial lungs.In our former research we developed several novel membrane materials for artificial lungs based on polysulfone(PSF)and poly-4-methyl-1-pentene(PMP).According to the macromolecules we grafted onto the membrane surface such as heparin and MPC,the gas channels were blocked,therefor caused loss in gas permeability.In this article we prepared PMP hollow fiber membrane(HFM)applying thermal induced phase separation(TIPS),after which we grafted heptafluorobutyric acid,2,2,3,3,4,4,4-heptafluoro-1-butanol and 1H,1H,2H-perfluoro-1-hexene onto the membrane surface using low temperature plasma treatment(LTPT).Modified membranes performed better in gas permeability and blood compatibility compared with pristine membranes.1.Study on grafting multi-fluoro components onto the surface of PMP HFMsIn this part PMP HFMs were prepared using thermal induced phase separation method,during which water was used as cooling agent.Mixture of dibutyl phthalate and dioctyl phthalate was used as polymer solvent,in ratio of 1:1.Temperature was determined from 230? to 210? during the procedure of melt extrusion.The dry spinning distance was controlled as 1 cm and the temperature of water as cooling agent was determined as 25±5?.The prepared HFMs has an outer diameter of 1190 ?m,inner diameter of 850 ?m,porosity of 64.6%.In this part we firstly conducted grafting heptafluorobutyric acid,2,2,3,3,4,4,4-heptafluoro-1-butanol onto the membrane surface using liquid grafting method,and grafting 2,2,3,3,4,4,4-heptafluoro-1-butanol,1H,1H,2H-perfluoro-1-hexene using gas grafting method.The operating parameters were optimized using contact angle as evaluating parameter.The optimized parameters are as followed:plasma treatment time of 20 min,treatment power of 120 w,Ar gas flow of 30 SCCM;in gas grafting treatment period,gas flow of 2 L/min,treating time of 40 min;in liquid grafting period,soak time of 16 h.The multi-fluoro molecules heptafluorobutyric acid,2,2,3,3,4,4,4-heptafluoro-1-butanol,1H,1H,2H-perfluoro-1-hexene were named as MF1,MF2,MF3,and modified membranes grafted with them were named as PMP-MF1,PMP-MF2,PMP-MF3 respectively in this article.The success of grafting were then verified by IR and XPS spectrum.2.Gas absorption,gas permeation experiments and Gaussian simulationIn this part the experiment of heptafluorobutyric acid,2,2,3,3,4,4,4-heptafluoro-l-butanol,1H,1 H,2H-perfluoro-1-hexene,perfluorotributylamine,perfluorooctane absorbing CO2 and O2 were conducted.The Henry's constants of the components to O2 were determined as 28.84×103 kPa,30.91×103 kPa,42.45×103 kPa,27.74×103 kPa,34.59×103 kPa.The Henry's constants of the components to CO2 were found as 10.59×103 kPa,12.43×103 kPa,42.81×103 kPa,15.96×103 kPa,12.01×103 kPa,The Henry's constants of perfluorooctane and perfluorooctane bromide to CO2 were 5.12×103 kPa and 4.75×103 kPa and the Henry's constants of perfluorooctane and perfluorooctane bromide to O2 were 19.5×103 kPa and 21.6×103 kPa,according to published articles.The interaction force between multi-fluoro components and CO2,O2 molecules were calculated using Gaussian09w,and all shown a qualitatively trend of MF1>MF2>MF3,which verified the experiment result.After that The CO2 and O2 gas permeability experiments of modified membranes were conducted.For PMP-MF1,PMP-MF2,PMP-MF3,the CO2 permeability results were 4.35 ml·(cm2·min·bar)-1,4.52 ml·(cm2·min·bar)-1 and 4.29 ml·(cm2·min·bar)-1,the O2 permeability results were 14.01 ml·(cm2·min·bar)-1,13.91 ml·(cm2·min·bar)-1 and 14.99 ml·(cm2·min·bar)-1.The gas permeability of the membrane grew after plasma treatment,based on what the permeability has been further raised to 25%compared with virgin membranes,due to the considerable capacity of multi-fluoro components absorbing O2,which were grafted onto the surface membrane.Gaussian simulation were also conducted by altering the structure of the molecules,in which the structure altered molecules were named as MF1+,MF2*,MF3+ to investigate the interaction force between grafting group and gas molecules.Results shown that the force with O2 ordered by MF3*>MF1*?MF2*,and the force with CO2 didn't differ a lot,which roughly verified the experiment results.3.Study of hemocompatibility of modified membranesIn this part the platelet adhesion experiments,protein adsorption experiments,APTT/PT tests of modified membranes were conducted.The platelets adhesion results of PMP-MF1,PMP-MF2,PMP-N93 were 1.33×107/cm2,1.29×107/cm2 and 1.25×107/cm2,decreased a lot compared to 4.12×107/cm2 of pristine membrane.The BSA adsorption results of three modified membranes were 15.2 ?g/cm2,16.9 ?g/cm2 and 14.1 ?g/cm2,reduced a lot compared to 32.3 ?g/cm2 of Virgin membrane.The FBG adsorption results of modified membranes were 21.9 ?g/cm2,23.4?g/cm2 and 20.8?g/cm2,decreased a lot compared to 55.9 ?g/cm2 of pristine membrane,In APTT test the results shown as 31.5 s,30.8 s and 36.4 s,better than 15.7 s of pristine membrane.In PT test the results shown as 13.2 s,13.2 s and 11.2 s,also got better compared to 9.5 s of virgin membrane.The results told that the hemocompatibility of the PMP HFMs were significantly improved in modified membranes.