Preparation And Properties Of Polymethacrylate Cryogel

Cryogel belongs to a kind of macroporous polymer material which has unique advantages,such as sponge-like structure,pores interconnecting,high selectivity,short diffusion path,low pressure drop,good biocompatibility,less time for adsorption and elution,et al.Moreover,it has been widely used in separating and purifing biomacromolecules.In the research,the poly（2-hydroxyethyl methacrylate-co-glycidyl methacrylate）（p（HEMA-GMA））cryogel was prepared by free-radical copolymerization at-16℃ using hydroxyethyl methacrylate（HEMA）as a structural monomer,glycidyl methacrylate（GMA）as a functional monomer,and N,N’-methylenebisacrylamide（MBAAm）as a crosslinker,ammonium persulfate（APS）as a initiator,and N,N,N′,N′-tetramethylene diamine（TEMED）as a accelerator.The effects of monomer concentration,molar ratio of monomer to crosslinker,freezing final temperature and cooling rate on its properties were also investigated.The scanning electron microscopy（SEM）showed that the prepared cryogel had interconnected pores size of 70-100μm.The result of swelling characteristics of water in the p（HEMA-GMA）cryogel showed that the swelling process of water in the cryogel conformed to the Fickian diffusion,and the swelling equilibrium can be basically achieved in the first 5 s.In addition,the iminodiacetic acid（IDA）functional group was grafted to p（HEMA-GMA）cryogel by the reaction of amine with epoxy groups,and then Cu²⁺,Ca²⁺,Fe³⁺ions were chelated onto the cryogel.Various factors affecting adsorption,such as the type of metal ions,protein type and concentration,and adsorption time,were also studied.Simultaneously,comparison of adsorption capacity of immobilized Cu²⁺,Ca²⁺,Fe³⁺affinity cryogels,we can see that the isotherm adsorption process of porcine pancreatic lipase（PPL）and bovine serum albumin（BSA）onto p（HEMA-GMA）cryogel was coincident with Langmuir model.And the p（HEMA）-Cu²⁺（0.5M）cryogel was the biggest.The effect of temperature on the adsorption of different proteins was different,the maximum PPL adsorption on the p（HEMA）-Cu²⁺（0.5M）cryogel was 150.14 mg/g at higher temperature（35℃）,the maximum BSA adsorption on the p（HEMA）-Cu²⁺（0.5M）cryogel was 154.11 mg/g at lower temperature（25℃）.The adsorption kinetic was described as the pseudo-second-order model,and the adsorption time of PPL and BSA onto the immobilized metal affinity cryogels at 25℃ and 35℃ getting to the equilibrium was about 12 h.The calculated Gibbs free energy（?G）of adsorption indicated that the adsorption process was spontaneous.Using p（HEMA-GMA）cryogel column as matrix,different concentrations of Na₂CO₃ and IDA were respectively circulated into the matrix by peristaltic pump,and the cryogel column was washed successively with 0.1 M acetic acid solution and distilled water,and then 0.5 M Cu²⁺was chelated.The p（HEMA）-Cu²⁺（0.5M）cryogel column was finally washed with a large amount of distilled water to remove free copper ions.By investigating the performance parameters of p（HEMA-GMA）and p（HEMA）-Cu²⁺（0.5M）cryogel columns,the height equivalent of theoretical plate（HETP）of p（HEMA）-Cu²⁺（0.5M）cryogel column was found that lower than p（HEMA-GMA）,which indicating that the addition of metal ions had a certain degree of influence on the pore distribution,pore size and roughness of the pore wall.The adsorption rate of proteins on the p（HEMA）-Cu²⁺（0.5M）cryogel bed was obviously affected by pH and ionic strength,and the injection flow rate did not affect the adsorption of protein on the cryogels.When the pH was 4.5,the adsorption rate of BSA and PPL on the p（HEMA）-Cu²⁺（0.5M）cryogel beds reached the maximum,which were52.29%and 45.65%,respectively;when the salt concentration was 0,the adsorption rate of BSA on the p（HEMA-GMA）and p（HEMA）-Cu²⁺（0.5M）cryogel beds reached9% and 22.3%,respectively.In summary,the adsorption capacity of cryogel for BSA can be greatly improved by modifying.Furthermore,through adjusting the pH and ionic strength,and the immobilized metal affinity cryogel can reach the maximum adsorption amount of BSA under the optimum conditions.When the NaCl solution reached 1 M,the BSA on the p（HEMA）-Cu²⁺（0.5M）cryogel bed could be effectively eluted.