Preparation Of Modified Cellulose Nanofibrous Membrane For Lysozyme Adsorption

In recent years, proteins with high purity are urgently required in variety of areas, involving bio-pharmaceutical, immunodiagnostics, immunotherapy and scientific research. Highly purification process is the key step for the production of proteins since it directly determines the purity and productive efficiency of protein products. Conventional methods such as gel chromatograph, centrifugation, precipitation and electrophoresis have been used to selectively adsorb and separate the target protein molecules in purification process. They generally suffer from the disadvantages of relatively complex operation, high cost, low target protein purity. So it is the key difficult problem to prepare the material which is suitable for mass production and has high adsorption performance in the process of protein purification.Nowadays, chromatography resins are the mostly used materials for protein separation and purification, while they generally have the problem of relatively slow adsorption kinetics, high operation pressure drops and long operation time due to the slow mass transfer rate of proteins in the materials since most of the adsorption ligands are distributed in the interior of these porous resin beads materials, caused their disability to meet well with the demand of the large scale and high speed industrial protein productions. Alternatively, fibrous membranes adsorption materials with large pore sizes could effectively decrease the using pressure-drops, but their small surface areas and low ligands distribution density caused by their relatively large fiber diameter seriously restrict their application in the industrial productions.Nanofiber membrane is a highly desirable scaffold for immobilization of ligands and capturing proteins owing to its large surface area to volume ratio, high tortuous porous structure and robust mechanical strength. The unique surface and interface effect of nanofiber membrane endows it good ability of modification. Cellulose has been widely applied in protein adsorption field due to its rich hydroxyl content which make it easy to be modified. At the same time, cellulose has advantages of rich source and low price. Cellulose nanofiber membrane possesses uniform mesh structure that large molecules can freely pass, so the membrane has outstanding and promising protein adsorption performance.We greatly increased the amount of active hydroxyl on the fiber surface and then got superhydrophilic cellulose nanofiber membranes together with good mechanical strength via the precise control of deacetylation process. Furthermore, they modified the obtained membranes by taking the bifunctional carboxyl coupling agent as the modification materials, then negative carboxyls were in situ grafted on the surface of nanofibers, which endowed the materials with effective protein adsorption and purification performance. The resultant materials exhibited a high lysozyme adsorption capacity of 160 mg/g, fast equilibrium within 12 h, and excellent reusability. Otherwise, the saturation dynamic adsorption capacity of the membranes under the drive of gravity reached up to 118 mg/g, which has a significant improvement compared with commercial regenerated cellulose materials. In addition, these materials also showed excellent durability and reusability performance owing to the strong chemical crosslinking structure between fibers formed in modification process and stable chemical properties of cellulose. This kind of protein adsorption nanofibrous membranes are expected to be widely used in various fields, containing pharmaceuticals, foodstuffs and cosmetics.