Composite Cryogel Embedded With SiO₂ Nanoparticles By Grafting Polymerization In Pores

Continuous cryogels have interconnected supermacropores with pore size of several to hundreds of microns. Ion-exchange cryogel monolithic chromatography is a new method for separation and purification of bioproducts, which is provided with high selectivity and applied to capture and separate target biomolecules directly from unclarified feedstocks or crude cell homogenates at high flow velocities. It permits the solid particulates in the culture fluids to pass through freely without blockage. This method has potential applications in bioseparation areas.A supermacroporous composite cryogel is introduced by embedded with different mass ratios of SiO₂ nanometer-size particles to acrylamide （AAm） monomer （0.01-0.08:1）. These composite cryogels were prepared by the radical cryogenic copolymerization of AAm, N,N-methylene-bis-acrylamide （MBAAm）, and the dispersed SiO₂ nanoparticles under the freezing-temperature variation conditions in glass columns. Values of the height equivalent to theoretical plate （HETP） of the cryogel beds at different liquid flow rates were obtained by measuring residence time distributions （RTDs） using tracer pulse-response method. The appropriate condition is as following: The cryogel prepared by using 0.02 mass ratios of SiO₂ nanoparticles to acrylamide monomer has best performance.We prepared cation-exchange cryogels by grafting of 2-acrylamido -2-methyl-1-propanesulfonic acid （AMPSA） onto polyacrylamide-based cryogel embedded with 0.02 mass ratios of SiO₂ nanoparticles by in-situ graft polymerization using potassium diperiodatocuprate （Cu（III） solution） as initiator. Chromatographic process of lysozyme in the composite cryogel after grafted with AMPSA was carried out to reveal the protein breakthrough and elution characteristics. The superficial velocity in that process can reach 15 cm/min, indicating the improvement of the mechanical strength due to the embedded nanoparticles.The effects of grafting conditions on the properties of an anion-exchange composite cryogel by grafting of N, N-Diethylaminoethyl methacrylate （DEAEMA） onto the composite cryogel matrix were investigated experimentally. The grafting conditions considered here included the concentrations of monomers and graft reaction time. The protein binding capacity increased with the decrease of the concentration of DEAEMA and the graft time in a wide range under the present conditions. The maximum binding capacity of lysozyme reached 2.13 mg/mL cryogel in these grafted cryogels with DEAEMA of 1 M and at the graft time of 1 h.