Rapid Separation of Human Hemoglobin on a Large Scale From Non-clarified Bacterial Cell Homogenates Using Molecularly Imprinted Composite Cryogels

Mass production of cation-exchange cryogels and their chromatographic adsorption performance for bioseparation

The preparation of cryogels with enhanced protein adsorption capabilities holds significant promise in bioseparation. The challenge of industrializing cryogels lies in achieving efficient large-scale production while maintaining controllable performance characteristics. In this work, 200 of poly (hydroxyethyl methacrylate) (pHEMA) monolithic cryogels were mass-produced per batch by cryo-polymerization. Subsequently, 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPSA) was employed as the functional monomer and the cation-exchange pHEMA-AMPSA cryogel discs were successfully prepared by monolith slicing and then stirring graft polymerization. The stable performance of pHEMA cryogel monoliths produced in each batch and the grafting efficacies of pHEMA-AMPSA cryogel discs across different grafting batches were demonstrated to be consistent. An average maximum static adsorption capacity of lysozyme was achieved as 86.5 mg·(mL cryogel discs)-1, which was higher than those cryogels reported in references. Furthermore, pHEMA-AMPSA cryogel discs were compressed into columns to create cryogel disc-packed beds under different compression ratios, and the effects of compression ratio and loading volume on the chromatographic performance of lysozyme were studied. The dynamic adsorption capacity of lysozyme in cryogel disc-packed bed at a compression ratio of 40 % was five times that of the uncompressed state based on an equivalent volume basis of cryogel discs, reaching 13.1 mg·(mL cryogel bed)-1 when loading 1 mg mL-1 lysozyme with a total volume of 355.8 mL. This work offers a simple approach to mass-producing ion-exchange materials with reliable performance and high adsorption capacity for bioseparation industry applications.

Molecularly Imprinted Polymers with Shape-Memorable Imprint Cavities for Efficient Separation of Hemoglobin from Blood

Efficient separation and purification of hemoglobin from blood and other complicated biological fluids still remains a big challenge. Molecularly imprinted polymers (MIPs) of hemoglobin are potential choices; however, they suffer from severe problems including difficult template removal and low imprinting efficiency like other protein-imprinted polymers. Herein, a novel MIP of bovine hemoglobin (BHb) was designed in which a peptide crosslinker (PC), instead of the commonly used crosslinkers, was used. The PC, a random copolymer of lysine and alanine, adopts an α-helical conformation at pH 10 but transits to a random coil conformation at pH 5. The introduction of alanine residues lowers the pH range at which the PC undergoes helix-coil transition. The imprint cavities in the polymers are shape-memorable due to the reversible and precise helix-coil transition of the peptide segments in the polymers. They can be enlarged by lowering pH from 10 to 5, thus allowing complete removal of the template protein under mild conditions. When the pH is adjusted back to 10, their original size and shape will be recovered. Therefore, the MIP binds the template protein BHb with high affinity. Compared with the MIP crosslinked with the commonly used crosslinker, the imprinting efficiency of the PC-crosslinked MIP is significantly improved. In addition, both the maximum adsorption capacity (641.9 mg/g) and imprinting factor (7.2) are much higher than the BHb MIPs reported previously. The new BHb MIP also exhibits high selectivity toward BHb and good reusability. Thanks to the high adsorption capacity and high selectivity of the MIP, when it was applied to extract BHb from bovine blood, BHb in the blood sample was extracted almost completely, and high purity product was obtained.

Interaction of haemin with albumin-based macroporous cryogel: Adsorption isotherm and fluorescence quenching studies

Albumin-based cryogels for capturing haemin were synthesised by crosslinking different biomolecules, bovine serum albumin (BSA) and ovalbumin (OVA). The impact of the protein and coupling agent concentrations on cryogel’s mechanical properties, swelling ratios and polymerisation yields, as well as autoclaving as a post-treatment on the cryogel, were studied. We found that BSA (50 mg/ml) and the crosslinker (N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride, 46 mg/ml) formed a cryogel with optimum physical characteristics at a comparatively low protein concentration. The cryogel’s mechanical stability was increased using a double-layer cryogel approach by crosslinking the BSA proteins at subzero temperature inside an acrylamide and hydroxyethyl methacrylate premade cryogels. Batch binding and kinetic adsorption isotherms of haemin on the cryogels were assessed to evaluate their binding capacity toward the porphyrin molecule. The results showed that single-layer cryogels (BSA and OVA) had a higher capacity (∼0.68 mg/ml gel) and higher reaction rate constant towards haemin adsorption than double-layer gels. In contrast, the double-layer cryogels had higher mechanical strength than single-layer gels. The experimental results suggested that the cryogels followed the Freundlich model and the pseudo-second-order isotherm for batch adsorption and kinetics, respectively. The interaction between haemin and the gels was studied by fluorescence quenching. We found between 1.1 and 1.6 binding sites for different cryogels.