PEI Grafting Epoxy-Functional Magnetic Microspheres And Its Application

Magnetic polymer microspheres with low cost,large specific surface area,small particle size,good stability and superparamagnetic,and can be rapidly separated under the action of an external magnetic field.It is widely used in immobilized enzymes,biomedicine,cell separation and other fields.In this paper,we studied the preparation,functional modification and application of poly?vinyl acetate??PVAC?magnetic microspheres.The main contents include the following parts.First,polyvinyl acetate magnetic microspheres were successfully prepared by suspension polymerization using oleic acid modified Fe₃O₄ as magnetic particle and vinyl acetate?VAC?as monomer.Under the optical microscope,the particle size distribution is between 20-40?m,and the monodisperse and spherical degree are better.After that,the magnetic microspheres were esterified to carry hydroxyl groups on the surface,then the epoxy chloropropane was modified to the hydroxyl group on the surface of the magnetic microsphere,and the epoxy group was introduced.The surface epoxy content of the magnetic microspheres was 718.1?mol/g.Subsequently,different molecular weight polyethylene imines?PEI 600,PEI 1800,PEI 70000?grafted onto the surface of magnetic microspheres,and prepare three kinds of magnetic microspheres to graft polyethyleneimine,PVAC-PEI600,PVAC-PEI1800 and PVAC-PEI70000 magnetic microspheres.The surface amino content of three kinds of magnetic microspheres measured by acid-base titration were 382.1,476.7 and195.4?mol/g microspheres respectively.The IR spectra showed that the magnetic microspheres have been successfully grafted with polyethyleneimine.Second,three kinds of PEI grafted magnetic microspheres were used as carriers to physically adsorb bovine serum albumin?BSA?.The effects of PEI with different molecular weights on protein adsorption were investigated,and compared with those of non grafted PEI magnetic microspheres for BSA adsorption.The results show that the magnetic microspheres after grafting PEI is obviously increased adsorption of BSA.The adsorption capacity of four magnetic microspheres for PVAC-PEI600,PVAC-PEI1800,PVAC-PEI70000 and PVAC was 87.8,74.5,52.0 and 46.0 mg/g,respectively.The effect of various factors on the adsorption of BSA in the adsorption process was further investigated in the experiment.The results showed that increasing the ionic strength would reduce the adsorption capacity of BSA,and the initial BSA concentration,temperature and pH have a significant effect on the magnetic microsphere adsorption BSA.When the concentration of BSA is 2.5 mg/mL,pH is7.0,and the temperature is 35?,the PVAC magnetic microspheres and PVAC-PEI600magnetic microspheres reached the maximum adsorption of BSA,and the maximum adsorption capacity were 46.0 and 88.1 mg/g.Third,PVAC-PEI600 magnetic microspheres were used to chelate with the transition metal ion Cu²⁺to prepare the PVAC-PEI600@Cu magnetic microspheres.The content of Cu²⁺was 360?mol/g.PVAC-PEI600@Cu magnetic microspheres were used as the carrier to adsorb bovine serum albumin?BSA?and compared with PVAC-PEI600 magnetic microspheres for the physical adsorption of BSA.The results showed that PVAC-PEI600@Cu magnetic microsphere had a higher adsorption capacity of BSA compared with PVAC-PEI600 magnetic microspheres,and the adsorption capacity of two magnetic microspheres to BSA were 99.7 and 82.0 mg/g,respectively.Fourth,using two magnetic microspheres of PVAC-PEI600 and PVAC-PEI600@Cu as the carrier and using glutaraldehyde as the crosslinker,the immobilized BSA was studied by crosslinking method.The results showed that cross-linking encapsulation method immobilized BSA is more stable than physical adsorption BSA.Furthermore,the conditions such as glutaraldehyde concentration,crosslinking time,crosslinking temperature and crosslinking pH on the immobilized BSA were investigated.The results showed that when the concentration of glutaraldehyde was 0.24‰,the crosslinking time was 90 min and crosslinking temperature was 30?,crosslinking pH was 7.0,the immobilization of PVAC-PEI600@Cu on magnetic microspheres and PVAC-PEI600 magnetic microspheres were the best.