Preparation And Application On Proteins Separation Of Cellulose Acetate-based Nanofibrous Membrane

In the recent past,the rapid growth in the field of biotechnology and bioscience has led to an increase in the worldwide demand for efficient,large-scale protein purification processes.Cellulose acetate as the start material,the structure and diameter distribution of nanofibrous membrane is improved by single solvent and binary system;Cellulose nano-fiber/Cellulose triacetate nanofibrous composite membrane,Cellulose diacetate nitrate nanofiber and Hydroxyapatite/Cellulose triacetate nanofiber composite membrane were prepared by solvent-exchange method,chemical modification and coaxial electrospinning,respectively.The prepared nanofibrous membranes were applied to separating Bovine serum albumin,Trypsine and Egg albumin.Firstly,cellulose acetate still has some drawbacks of processing technology such as lack of solvent systems,large fiber size and wide fiber diameter distribution.In order to optimize the structrue of fibre substrates,smooth and uniform nanofibers could be obtained from a solution of cellulose acetate in the single solvent and binary systems.Among these single solvents,only trifluoroacetic acid?TFA?can directly prepare cellulose diacetate?CDA?and cellulose triacetate?CTA?nanofibrous membranes.However,TFA cannot optimize the fiber diameter and distribution of CDA and CTA membranes by changing solvent composition.Continuous and uniform CDA nanofibers and nanofibrous membranes with average fiber diameter down to194 nm were electrospun in binary system such as acetone/dimethylacetamide?DMAc?.In a new binary system,DMSO had been used as co-solvent to lower the viscosity,increase the conductivity,and to lower the surface tension of CTA solution.Besides,the chloroform,which has a comparatively high vapor pressure,rapidly evaporates while the entangle-ments of the polymer chains prevent the jet from breaking up.DMSO/chloroform co-solvent system produced long and smooth CTA nanofibers with lowest mean diameters of about 194 nm,exceed 50%fiber diameters is between 100 and 300 nm.Secondly,cellulose nanofibers?CNFs?have large amounts of carboxylate groups,which could serve as adsorption sites for proteins and enzymes.On the other hand,CNFs also enable form a stable nanofiber suspension in DMSO.Firstly,TEMPO-oxidized Bamboo CNFs?4nm⁸nm?was transfer from water to DMSO by solvent-exchange method.CNFs/CTA nanofibrous composite membranes weresuccessfully prepared by uniaxial electrospinning.Smooth and uniform composite nanofibers with mean diameters of about 430±120 nm could be obtained from a solution of CNFs/CTA in the DMSO/chloroform,exceed 70%fiber diameters are between 300 and 600 nm.CNFs/CTA nanofibrous composite membrane has the abilities to adsorb BSA,Trypsine and Egg albumin.After five adsorption-desorption cycle tests,the 80%adsorbed proteins can be eluted from CNFs/CTA nanofibrous membranes.Thirdly,the objective of this research is to improve the proteins adsorption abilities of cellulose diacetate?CDA?.Cellulose diacetate nitrate?CDNA?was synthesized by nitration of cellulose diacetate?CDA?,using HNO₃/CH₂Cl₂ as nitration agent.Five solvents,that is,acetone,dimethylacetamide?DMAc?,dimethyl sulfoxide?DMSO?,chloroform,and acetic acid were used to generate co-solvents for electrospinning CDNA nanofibrous membranes.Long uniform CDNA nanofibers were electrospun from a 15 wt%CDNA solution in DMSO/chloroform?2/1,v/v?,exceed 70%fiber diameters is between 100 and 250 nm.CDNA nanofibrous membrane has the abilities to adsorb BSA,Trypsine and Egg albumin.The membrane showed reusability after regeneration with elution buffer.In order to increase the number of adsorption sites of the surface of cellulose triacetate?CTA?nanofibers,three kinds of hydroxyapatite?HAp?/CTA nanofibrous composite membranes were prepared by physical blending,single and coaxial electrospinning.The results showed that coaxial electrospinning process obviously reduces the extent of agglomeration?clusters of HAp nanoparticles held together by weak forces?.The HAp nanoparticles were successfully incorporated on the surface of CTA fibers.It is conceivable that the well-dispersed HAp particles can improve the number of protein binding sites on the surface of CTA?core?-HAp?sheath?nanofibers.The morphologies of CTA?core?-HAp?sheath?nanofibers are quite uniform,and no bead formation.Fiber diameters are mostly around 220 nm,with no fibers'diameters higher than 350 nm.CNFs/CTA nanofibrous composite membrane has different abilities to adsorb BSA,Trypsine and Egg albumin,but the difference was not significant.After five adsorption-desorption cycle tests,the 70%adsorbed proteins can be eluted from CTA?core?-HAp?sheath?membranes.