Study On Cellulose/Graphene Oxide Composite Microsphere For Bilirubin Adsorption

Bilirubin is an endogenous toxin in human body,which is produced by heme metabolism in red blood cells.When liver function is damaged,the accumulation of free bilirubin in blood will lead to hyperbilirubinemia through blood circulation,causing jaundice,and even brain and nervous system diseases.Hemoperfusion is often used to remove excess bilirubin in clinic,and safe and efficient bilirubin adsorbent is the key.At present,the adsorption efficiency of bilirubin adsorbent in clinical application is low,and it is difficult to eliminate the interference of carrier albumin on bilirubin adsorption process.Therefore,the preparation of a safe,efficient and specific bilirubin adsorbent has important research significance.In this study,microcrystalline cellulose（MCC）with good biocompatibility and graphene oxide（GO）with rich oxygen functional groups on the surface and high adsorption to bilirubin were selected as raw materials to prepare MCC/GO composite microspheres with porous structure,and efficient adsorption of bilirubin was achieved through hydrogen bonding,π-π interaction and hydrophobic effect.The affinity ligands D-glucuronic acid and L-lysine that selectively adsorb bilirubin in albumin solution can functionally modify the MCC/GO composite microspheres,and two functionalized MCC/GO composite microspheres were prepared.Thereby realizing the efficient and specific adsorption of bilirubin by the adsorbent.The main research contents of this paper are as follows:（1）Preparation and study of MCC/GO composite microspheres.The alkali/urea system was used as the solvent to realize the dissolution of MCC and the dispersion of GO.Epichlorohydrin（ECH）was introduced to crosslink MCC.MCC/GO composite microspheres were prepared by dropping method,solution exchange regeneration and freeze-drying.The structure and properties of composite microspheres with different GO addition were studied.The results showed that the addition of GO effectively promoted the pore formation of microspheres.When the amount of GO was 10%,the microspheres had a three-dimensional macroporous structure with internal and external penetration.At this time,the porosity of microspheres was 73.2%,which was conducive to the effective mass transfer and adsorption in the process of bilirubin adsorption.（2）Study on the adsorption properties of MCC/GO composite microspheres for bilirubin.The effects of different GO addition amount,initial bilirubin concentration,temperature,ionic strength,pH value,BSA concentration and other factors on bilirubin adsorption were explored.The adsorption mechanism was explored through the fitting of kinetic model and isothermal adsorption model,and the reusability of microspheres was explored through cyclic test.The results showed that the addition of GO could effectively improve the adsorption capacity of microspheres for bilirubin.When the addition of GO was 10%,the maximum adsorption capacity and removal rate were 100.0 mg/g and 53.2% respectively.The adsorption process of bilirubin on microspheres accorded with pseudo-secondary kinetic model and Freundlich isothermal adsorption model.With the concentration of BSA increasing to 200 mg/L,the adsorption capacity of bilirubin decreased to80.5 mg/g,and the adsorption capacity of BSA was 46.7 mg/g.（3）Preparation of functionalized MCC/GO composite microspheres and their adsorption properties for bilirubin.With D-glucuronic acid and L-lysine as ligands,respectively,loading on the MCC/GO composite microspheres was achieved by a ring-opening reaction with epoxidized cellulose,two kinds of functional composite microspheres were obtained.The effects of functional modification on the structure,properties and bilirubin adsorption properties of the microspheres were studied.The results showed that the adsorption performance of the modified functional microspheres for bilirubin was significantly improved,and the adsorption process accorded with the pseudo-secondary kinetic model.The adsorption capacities of D-glucuronic acid functionalized microspheres and L-Lysine functionalized microspheres for bilirubin were 134.6 mg/g and 120.6mg/g respectively.In BSA solution,they still were 108.5 mg/g and 120.6 mg/g respectively.And the adsorption capacity of BSA decreased to 7.0 mg/g and 8.6 mg/g respectively.Compared to other adsorbents,it better realized the efficient and specific adsorption of bilirubin.In conclusion,cellulose/graphene oxide（MCC/GO）composite microspheres were prepared in this study,and affinity ligands were introduced for functional modification,which effectively improved the adsorption of bilirubin,especially the specific adsorption capacity.This study will provide some reference for the follow-up study of bilirubin materials.