摘要
本文通过共沉淀法制得了Fe_3O_4磁性纳米颗粒,进而用一定量的油酸对Fe_3O_4纳米颗粒表面进行改性,得到了亲油性的磁流体。分别采用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)、透射电子显微镜(TEM)、振动样品磁力计(VSM)分析了改性Fe_3O_4纳米颗粒的结构、粒径及粒径分布、形态和磁性能。所得结果表明:改性后Fe_3O_4纳米颗粒表面带有油酸,粒径分布在10-15nm之间,呈超顺磁性。
以十二烷基硫酸钠(SDS)为乳化剂,二乙烯基苯(DVB)作为交联剂,在亲油性磁流体存在的条件下,采用细乳液聚合法分别使单体甲基丙烯酸甲酯(MMA)与甲基丙烯酸缩水甘油酯(GMA)、苯乙烯(St)与2-丙烯酰胺基-2-甲基丙磺酸(AMPS)聚合,制得了PMMA-co-PGMA和PSt-co-PAMPS磁性复合微球,并进一步对PMMA-co-PGMA磁性微球进行表面改性,制得了表面带氨基的PMMA-co-PGMA-NH2磁性复合微球,由线性电位滴定法测得微球表面氨基含量为431μmol/g。并用FTIR、TEM、热失重(TG)和VSM对两种磁性复合微球的结构、形态和尺寸、磁含量以及磁性能进行了表征,结果显示PSt-co-PAMPS和PMMA-co-PGMA磁性复合微球的粒径分布均匀,平均粒径均为170nm,PMMA-co-PGMA复合微球的磁含量可以控制在20%-50%之间。
利用疏水和静电作用,制得的PSt-co-PAMPS磁性微球可以物理吸附蛋白质;经过戊二醛修饰后,PMMA-co-PGMA-NH2磁性微球表面带上醛基,可共价连接蛋白质。将两种微球应用在牛血清蛋白(BSA)的吸附中,结果证明,比起PSt-co-PAMPS微球的物理吸附,采用化学吸附的PMMA-co-PGMA-CHO微球有更大的吸附量,能更快的达到吸附平衡,并且对BSA的结构影响更小,在蛋白吸附中更有优势。进而研究了PMMA-co-PGMA-CHO磁性复合微球固定化木瓜蛋白酶。相比自由酶,制得的固定化酶有更好的温度和pH适应性,而且能保存较长时间。
Fe_3O_4 nanoparticles were synthesized by precipitation method. The surfaces of Fe_3O_4 nanoparticles were modified by oleic acid to obtain hydrophobic magnetic fluid. The properties of the hydrophybic Fe_3O_4 nanoparticles, such as structures, diameter and diameter distribution, morphologies and magnetic properties were characterized by Fourier transformation infrared (FTIR), X-ray diffraction(XRD), transmission electron microscopy (TEM) and Viberating sample magnetism (VSM) separately. The results showed that the nanoparticles with oleic acid on their surface were superparamagetism, and the diameter was between 10-15nm.
Poly(methyl methacrylate)-co-poly(glycidyl methacrylate) (PMMA-co-PGMA) and polystyrene-co-poly(2-acrylanmido-2-methyl propanesulfonic acid) (PSt-co-PAMPS) magnetic composite microspheres were obtained by miniemulsion polymerization using sodium lauryl sulfate (SDS) as emulsfier and divinylbenzene (DVB) as crosslinker in the presence of magnetic fluid. The epoxy groups were modified to form amino groups on the surfaces of magnetic composite microspheres. The amount of amino groups was 431μmol/g, which was quantitatively determined by linear potentiometric titration method. The structures, morphologies, diameter and diameter distribution, magnetic properties and magnetism contents of the microspheres were characterized by FTIR, TEM, VSM and TG respectivly. The PSt-co-PAMPS and PMMA-co-PGMA were both uniform sized and the mean sizes of the microspheres were 170nm. The magnetism contents of PMMA-co-PGMA microspheres were controlled in the range of 20%-50%. Both of them were superparamagetism.
PMMA-co-PGMA-NH2 microspheres could immobilizatize bovine serum albumin (BSA) by covalent adsorption after modified by glutaraldehyde (GA). However, PSt-co-PAMPS microspheres could immobilizatize BSA by physical adsorption. The immobilization behavior of microspheres was compared. The amount of immobilized BSA on PMMA-co-PGMA-CHO microspheres was more than that on PSt-co-PAMPS microspheres and PMMA-co-PGMA-CHO microspheres need less time to reach immobilization equilibrium. It means that covalent interaction had an advantage on BSA immobilization.
As the PMMA-co-PGMA-CHO microspheres were preferable in respect of protein immobilization. They were chosen as carrier of the papain. The reaction condition for immobilization of enzyme was optimized and the difference of immobilized enzyme and free enzyme was investigated.
引文
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