Kaifeng Du

Preparation and characterization of novel macroporous cellulose beads regenerated from ionic liquid for fast chromatography.

Macroporous cellulose beads (MCB) used as anion exchangers were successfully prepared from cellulose solution in ionic liquid by double emulsification followed by cross-linking and modification with diethylaminoethyl. The pore structure and properties of the MCB were investigated and the results were compared with homogeneous cellulose beads (HCB). The MCB in size of about 71 microm is characterized by two sets of pores, i.e., diffusion pores (10-20 nm) and macropores (800-2000 nm), determined by mercury porosimeter. In addition, the bed permeability and effective porosity for BSA of MCB-packed column are 58% and 25% higher than those of HCB-packed column, respectively. The adsorption properties of MCB were evaluated, and compared with HCB and commercial absorbent (Sepharose 6 Fast Flow, CSFF). It is found that the pore diffusivity of BSA in MCB is over 7.9 times higher than HCB, and 6.7 times higher than CSFF, respectively. While the equilibrium adsorption capacity (q(m)) of BSA on MCB is obviously lower than that on HCB and CSFF, the dynamic binding capacity (DBC) on MCB at 10% breakthrough reaches 47.7 mg/mL, higher than HCB (40.3mg/mL) and CSFF (46.2mg/mL) at flow rate of 360 cm/h. In addition, the MCB-packed column showed better column efficiency over the HCB packed one. Therefore, we demonstrated that the MCB possessed more advantages than other ones, like HCB and CSFF, and was expected as an ideal material for fast chromatography.

Fabrication of superporous agarose beads for protein adsorption: effect of CaCO3 granules content.

Agarose gels were fabricated by water-in-oil emulsification with the addition of CaCO(3) granules at 8-16 wt%. Thus agarose beads of different superporosities were produced after dissolving the solid porogen. The superporous agarose (SA) and homogeneous agarose gels were double cross-linked and modified with diethylaminoethyl chloride to produce anion exchangers. We have proposed to use a superporous replica (porous titania microspheres) to examine the superporous structure and pore size distribution of the soft gel. The replica was prepared with the agarose gel entrapping CaCO(3) granules by a sol-gel-templating method. It was found that the superpores created by CaCO(3) granules were uniformly distributed and ranged from 0.95 microm to 1.33 microm. The physical properties of the gels were significantly affected by the porogen content. Importantly, by increasing the solid porogen to 12 wt%, the bed permeability and effective porosity increased about 48% and 33%, respectively. Further increase in the porogen to 16 wt% led to a decrease of the mechanical strength. With increasing superpores in the beads, the dynamic adsorption capacity of the packed columns increased obviously at 305-916 cm/h. Besides, the column efficiency changed less with increasing flow velocity up to 1200 cm/h. It was concluded that the use of 12 wt% CaCO(3) granules in agarose solution was beneficial for the fabrication of the SA gel with good mechanical stability and promising performance for protein chromatography.

Fabrication and characterization of aligned macroporous monolith for high-performance protein chromatography.

In the present study, a freeze casting method combined with particle accumulation was applied to fabricate the aligned macroporous monolith for high-performance protein chromatography. For the preparation, the reactive colloids were first prepared by using glycidyl methacrylate and ethylene glycol dimethacrylate as monomers. Subsequently, these colloids accumulated regularly and polymerized into the aligned macroporous monolith. The aligned porous structure of the monolith was characterized by SEM, mercury intrusion, and flow hydrodynamics. The results revealed that the generated monolith was possessed of aligned macropores in size of about 10 μm and high column permeability. Finally, after being modified with sulfonated groups, the monolith was evaluated for its chromatographic performance. It demonstrated that the aligned macropores endowed the monolith with excellent adsorption capacity and high column efficiency.

Peptide immobilized monolith containing tentacle-type functionalized polymer chains for high-capacity binding of immunoglobulin G

A peptide immobilized tentacle-type monolith is developed here for high-performance IgG purification. In this work, the glucose-anchored GMA molecules serve as monomers to be grafted into the tentacle-type chains on highly porous monolith by a series of chemical reactions. While maintaining high column permeability, the tentacle grafting endows the monolith with lots of reactive handles to anchor more peptides. With that, the grafted monolith shows high peptide density of about 155μmolmL(-1), up to approximately 4.7 times higher over the ungrafted one (33μmolmL(-1)). As a result, the static adsorbing capacity and dynamic adsorption capacity at 50% breakthrough point reach 101.8 and 83.3mgmL(-1) for IgG adsorption, respectively. Regeneration, recycle and reuse of grafted monolith are highly successful for 25 runs without obvious capacity loss. By taking these advantages of high capacity and excellent structure stability, the affinity grafted monolith is evaluated by using cleared human blood supernatant. And the result shows the peptide immobilized tentacle type monolith displays excellent specificity and high effectiveness for IgG purification.

Ionic liquid-regenerated macroporous cellulose monolith: Fabrication, characterization and its protein chromatography

Macroporous cellulose monolith as chromatographic support was successfully fabricated from an ionic liquid dissolved cellulose solution by an emulsification method and followed by the cross-linking reaction and DEAE modification. With the physical characterization, the cellulose monolith featured by both the interconnected macropores in range of 0.5-2.5μm and the diffusion pores centered at about 10nm. Given the bimodal pore system, the monolith possessed the specific surface area of 36.4m2g-1 and the column permeability of about 7.45×10-14m2. After the DEAE modification, the anion cellulose monolith was evaluated for its chromatography performances. It demonstrated that the static and dynamic adsorption capacity of BSA reached about 66.7mgmL-1 and 43.9mgmL-1 at 10% breakthrough point, respectively. The results were comparable to other chromatographic adsorbent. In addition, the proteins mixture with different pI was well separated at high flow velocity (611.0cmh-1) and high protein recovery (over 97%), proving the macroporous cellulose monolith had excellent separation performance. In this way, the prepared cellulose monolith with bimodal pores system is expected for the potential application in high-speed chromatography.