The Preparation And Mechanism Study Of Bio-based PLA Membrane For Hemodialysis

As kind of bio-based material, poly (lactic acid)(PLA) presents outstanding biocompatibilityand controlled degradation. It can also be made into porous separation membrane because of itsfavorable film-forming property. In this study, the PLA is applied to prepare ultrafiltrationmembrane through non-solvent induced phase inversion method. Studies involve the influence ofkind of solvents, kind of additives and molecular of additives on micro-structure and permeationperformance of PLA flat membrane, the influence of bore liquid content, spinning solutionextruded velocity, air gap and coagulating bath content on the micro-structure, inner diameter andwall thickness, the change of biocompatibility of PLA membranes before and after combingheparin on surface.SEM, FITR, Water flux instrument etc. are used to determine the cellular structure,transmittance of different molecular solute and biocompatibility of membranes prepared bydifferent condition. Results are as follows:(1) Asymmetric membrane with compact surface and finger-like cross section can be made ifsolvent with strong polarity like N-Methyl-2-pyrrolidone (NMP) is applied. Both polyethyleneglycol (PEG) and polyvinylpyrrolidone (PVP) can be pore-making, but the effect of latter one ismore significant, which enlarge the surface pore scale from10nm to40nm. Inner-connective pores,with better mechanical property and permeation performance comparing to finger-like pore, will beobtained if polyethylene oxide (PEO) with molecular100KDa is used as porogen. Meanwhile therelative mass fraction of PLA and PEO will affect the ratio of inner-connective structure.(2) There is a spongy compact layer in the middle of PLA hollow fiber when PEG is used asadditives, which can reduce the water flux. However, the spongy compact layer can be eliminatedby adjusting spinning solution extruded velocity and bore liquid flowing velocity. Different fromthe PLA flat membrane preparing, the inner-connective pores cannot always be obtained bydry-wet spinning method, even under the quite same solution composition. The improvement of airgap and NMP concentration in coagulating bath content is both beneficial to eliminate thefinger-like pores and effective on the membrane diameter and surface porosity. (3) Heparin can be successfully immobilized to surface of PLA membrane based on theself-polymerization and adhesive property of dopamine, and chemical reaction betweenpolydopamine and heparin. PLA membranes which are heparinzed show better blood compatibility,including fewer platelet adhesion, longer plasma recalcification time and decreased hemolysisratio.