Preparation Of New Affinity Membrane And Its Bilirubin Adsorption

Bilirubin is an endogenous toxin,and it can cause multiple organ failure in severe cases if excessive bilirubin accumulates in the body.The development of new bilirubin adsorbents is the key to use hemoperfusion in clinical treatment.As a type of new adsorption and separation materials,affinity membrane can be used to adsorb and separate some components from blood specifically by blending or chemical modification to graft ligands for specific adsorption.In this paper,Chitosan（CS）with a good biocompatibility was used as the base membrane material,and the inorganic nanomaterial graphene（GR）was blended into it to prepare a CS/GR blend membrane for bilirubin adsorption and separation.On the other hand,Cibacron blue F3GA（CBA）as ligand was immobilized onto cellulose acetate/polyethylenimine membrane（CA/PEI membrane）to prepare a dye-modified affinity membrane（CA/PEI-CBA membrane）for bilirubin adsorption.（1）The molecular model of CS and GR were constructed in Materials Studio and the interactions between CS/GR and bilirubin molecules were simulated under the NPT ensemble with the Sorption module.The results showed that the density of the system increased by 35%and the cell length decreased by 12%with the extension of the simulation time,both of which demonstrated the structural changes after blending.The average loading capacity of bilirubin increased with the simulation steps reached 30.9,which was 2.4 times and 14 times higher than CS or GR,respectively.（2）The CS/GR blend membrane was prepared by blending GR in CS-acetic acid solution to form a gelatinous substance,and scraped onto the PTFE,dissolving in sodium hydroxide solution by phase inversion method.XRD results showed a characteristic diffraction peak of graphene added at 2θ=26.5°,and XPS results showed that the characteristic peak of graphene appeared in the C1s peak spectrum.Both of these results prove the introduction of graphene.The CS/GR blend membranes with different mass fractions of GR were prepared.When the mass fraction of GR in the CS/GR solution was 2.0 wt%,i.e.CS/GR-2.0 membrane,it had a strong infrared absorption peak of acetamide group around 1750 cm^-1,and its bilirubin adsorption capacity was the highest.The effects of adsorption conditions on the bilirubin adsorption capacity of CS/GR blend membrane were also investigated.The best adsorption conditions of CS/GR blend membrane was 120 min at 37℃,and the saturated adsorption capacity was170.8 mg·g^-1.The adsorption process fits with Freundlich isothermal adsorption model,and the adsorption kinetics conforms to the second-order adsorption kinetics model.（3）The CA/PEI-CBA membrane was prepared through the main steps include dyeing,fixing and cleaning,the characterization was carried out by ATR-FTIR,XPS and SEM,etc.The ATR-FTIR and XPS results of CA/PEI-CBA membrane indicated the success of CBA molecules’immobilization.The effects of reaction temperature,reaction time and CBA concentration on both bilirubin adsorption capacity and weight loss of the dye-modified membrane were investigated and optimized by orthogonal and unilateral experiments.The bilirubin adsorption capacity of dye-modified membrane increased with both reaction time and the CBA concentration.However,with the increase of reaction temperature,the weight loss of the dye-modified membrane increased and the membrane matrix structure was destroyed due to hydrolysis.Under the conditions that reaction temperature was 30℃,CBA concentration was 5 mg·m L^-1,and reaction time was 4 h,the manufactured dye-modified membrane maintained a perfect porous structure,which was conducive to the full contact between bilirubin and CBA molecules,and showed good adsorption performance.The effects of reaction conditions on the bilirubin adsorption capacity were investigated by static adsorption experiments.The adsorption process fits with Freundlich isothermal adsorption model,and the adsorption kinetics conforms to the second-order adsorption kinetics model.