刷状结构的阳离子性接枝微粒QPDMAEMA/SiO2对牛血清白蛋白的吸附特性

以微米级硅胶微粒为基质, 通过接枝聚合和大分子反应, 制备了具有刷状结构的阳离子性接枝微粒, 深入研究了其对牛血清白蛋白(BSA)的强吸附能力、吸附机理和吸附热力学. 首先使含叔胺基团的单体甲基丙烯酸二甲基氨基乙酯(DMAEMA)在硅胶微粒表面发生接枝聚合, 制得接枝微粒PDMAEMA/SiO₂, 然后以氯乙胺为试剂, 使接枝大分子PDMAEMA链中的叔胺基团发生季铵化反应, 获得了具有刷状结构的阳离子聚电解质的功能接枝微粒QPDMAEMA/SiO₂. 测定了微粒QPDMAEMA/SiO₂的zeta 电位, 实施了对BSA的等温吸附实验, 考察了介质pH值、离子强度及温度对吸附作用的影响, 研究了吸附热力学. 研究结果表明, 功能接枝微粒QPDMAEMA/SiO₂ 比接枝微粒PDMAEMA/SiO₂ 具有更高的zeta 电位, 在静电相互作用驱动下, 微粒QPDMAEMA/SiO₂对BSA具有很强的吸附能力. 吸附容量随介质pH值的增大呈现先增大后减小的变化趋势,当pH值等于BSA的等电点(pI=4.7)时, 具有最高的吸附容量(高达112 mg·g^-1). 以等电点为界, 离子强度对吸附容量会产生完全相反的影响作用: 当介质pH值小于BSA的等电点时, 电解质浓度增大, 吸附容量增高; 当介质pH值等于BSA的等电点时, 吸附容量几乎不随电解质的浓度发生变化. 吸附过程熵值减小而且放出热量,是一个焓驱动的吸附过程.

Adsorption Characteristics of Bovine Serum Albumin on Cationic Grafted Particles QPDMAEMA/SiO2 with Brush Structure

Cationic grafted particles with a brush structure were prepared with micron-sized silica gel particles as a matrix via graft-polymerization and macromolecular reaction. The adsorption ability, adsorption mechanism, and adsorption thermodynamics of bovine serum albumin (BSA) on the particles were investigated in depth. The tertiary amine group-containing monomer (dimethylaminoethyl methacrylate, DMAEMA) was first allowed to polymerize on the surfaces of silica gel particles by initiating the ―NH₂/S₂O_82- surface system, resulting in grafted PDMAEMA/SiO₂ particles. Subsequently, the tertiary amine groups in the chains of the grafted PDMAEMA macromolecules were quaternized with chlorethamin reagent to obtain the functional grafted QPDMAEMA/SiO₂ particles, on which the cationic polyelectrolyte QPDMAEMA macromolecules were grafted. The zeta potential of the QPDMAEMA/SiO₂ particles was determined to estimate their surface electrical property. Isothermal adsorption experiments were carried out to investigate the effects of several main factors, including the pH value of the medium, ion strength, and temperature, on the adsorption performance of QPDMAEMA/SiO₂ particles. Finally, the adsorption thermodynamics were investigated. The results showed that the functional grafted QPDMAEMA/SiO₂ particles had much higher zeta potential than PDMAEMA/SiO₂. BSA would be very strongly adsorbed on QPDMAEMA/SiO₂ particles through electrostatic interactions. The adsorption capacity first increased and then decreased with increasing pH value, and it had a maximum value of 112 mg·g^-1 when the pH value of the medium was equal to the isoelectric point of BSA (pI=4.7). On both sides of the isoelectric point, the effect of ion strength on the adsorption capacity was opposite. When the pH value of the medium was lower than the isoelectric point of BSA (i.e., pH<4.7), the adsorption capacity increased with increasing concentrations of electrolyte (NaCl). When the pH value of the medium was equal to the isoelectric point of BSA (i.e., pH=4.7), the adsorption capacity was almost unchanged with ion strength. The adsorption process was exothermic and during this process the entropy tended to decrease. Furthermore, this adsorption process was driven by enthalpy.