Coating of nanoparticles on cryogel surface and subsequent double-modification for enhanced ion-exchange capacity of protein

• Nanoparticles (NPs)-coated cryogel provided larger specific surface area.
• Cryogel ion-exchanger was fabricated by NPs-coating and double modifications.
• Protein capacity was 4.2 times increased by the coating and double modifications.
• Column efficiency and capacity decreased only slightly from 0.6 to 12 cm/min.

A novel composite cryogel monolith was developed by coating poly(glycidyl methacrylate) nanoparticles (NPs) onto the pore wall surface of poly(acrylamide) cryogel. The NPs-coated column was double-modified with poly(ethylenimine) (PEI) and diethylaminoethyl in sequence. Scanning electron microscopy revealed the dense coating of the NPs on the cryogel surface, but the NPs-coating did not result in distinct changes of the column porosity and permeability. The rough pore wall surface and extended polymer chains offered more binding sites, so the dynamic binding capacity of the composite cryogel bed for bovine serum albumin reached 11.7 mg/mL bed volume at a flow rate of 6 cm/min, which was 4.2 times higher than that of the cryogel bed modified with PEI without coating NPs (2.8 mg/mL). The binding capacity as well as column efficiency decreased only slightly with increasing flow rate from 0.6 to 12 cm/min. The results indicated that the strategy of NPs-coating incorporating with double ion-exchanger modifications is promising for enhancing cryogel capacities, and the novel material would be useful for high-speed protein chromatography.