Preparation of molecularly imprinted polymer microspheres and their adsorption performance for 5α-cholestane
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摘要: 采用沉淀聚合法,以胆固醇、去氧胆酸、β-谷固醇为虚拟模板,丙烯酸(AA)为功能单体,偶氮二异丁腈(AIBN)为引发剂,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,制备甾烷类分子印迹聚合物(MIPs)和空白分子印迹聚合物(NIP)。采用扫描电子显微镜(SEM)、X射线光谱(XRD)、傅里叶变换红外光谱(FT-IR)和比表面积(BET)表征聚合物形貌和结构,并考察其对甾烷类物质的吸附性能。分析结果表明,甾烷类分子印迹聚合物尺寸均一、分散性好,是表面密布孔穴的球形纳米颗粒。吸附性能研究结果表明,MIPs对5α-胆甾烷的吸附能力明显强于NIP,且三种MIPs相比,去氧胆酸、β-谷固醇分子印迹聚合物对5α-胆甾烷的吸附强于胆固醇分子印迹聚合物。通过吸附动力学研究发现,MIPs对5α-胆甾烷的吸附过程符合准二级动力学模型,主要受化学吸附控制;MIPs和NIP的等温吸附符合Langmuir等温吸附模型和Scatchard模型,表明MIPs对5α-胆甾烷具有特异选择性吸附能力,且吸附过程属于单分子层吸附,最大吸附量为0.735 mg/g。表明胆固醇、去氧胆酸、β-谷固醇三种虚拟分子印迹聚合物均对5α-胆甾烷具有较高的分子识别能力及选择性。Abstract: Steroidal molecularly imprinted polymers (MIPs) and non-imprinted polymer (NIP) were prepared by precipitation polymerization method using cholesterol, deoxycholic acid, and β-sitosterol as the virtual templates, acrylic acid (AA) as the functional monomer, azobisisobutyronitrile (AIBN) as the initiator, and ethylene glycol dimethacrylate (EGDMA) as the cross-linking agent. The morphology and structure of the polymers were characterized using scanning electron microscopy (SEM), X-ray spectroscopy (XRD), Fourier-transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) specific surface area analysis. The adsorption performance for steroidal substances was also investigated. The results showed that the steroidal MIPs were uniformly-sized and well-dispersed spherical nanoparticles with porous surface. Adsorption performance results showed that MIPs had significantly stronger adsorption capacities for 5α-cholestane compared to NIP. Among the three MIPs, deoxycholic acid and β-sitosterol MIPs demonstrated stronger adsorption capacities for 5α-cholestane than that of cholesterol. The adsorption kinetics studies showed that the adsorption process of MIPs for 5α-cholestane was in accordance with the pseudo-second-order kinetic model, which was mainly controlled by chemisorption. The isothermal adsorption of both MIPs and NIP conformed to the Langmuir isothermal adsorption model and the Scatchard model, indicating that MIPs exhibited specific selective adsorption for 5α-cholestane and that the adsorption process was monolayer adsorption, with a maximum adsorption capacity of 0.735 mg/g. The study suggests that MIPs prepared with cholesterol, deoxycholic acid, and β-sitosterol as virtual templates have high molecular recognition and selectivity for 5α-cholestane.
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表 1 实验试剂
Table 1. Experimental reagents
表 2 实验仪器
Table 2. Experimental apparatus
实验仪器 型号 生产厂家 紫外可见光度计 UV-2600 谱质分析检测技术(上海)有限公司 电热恒温干燥箱 XMA-2000 泰科施普(北京)技术有限公司 恒温培养振荡器 HNY-100β 天津市欧诺仪器仪表有限公司 超声波清洗器 KQ5200 E 昆山市超声仪器有限公司 傅里叶红外光谱仪 Bruker Alpha 泰科施普(北京)技术有限公司 场发射扫描电子显微镜 Merlin Compact 德国蔡司 GC-MS HP Agilent 6890/5737 美国安捷伦科技有限公司 表 3 MIPs和NIP的比表面积、孔径及孔体积
Table 3. BET specific surface area, pore size and pore volume of MIPs and NIP
性能 MIP1 MIP2 MIP3 NIP 比表面积/(m2/g) 4.612 3.422 2.649 2.408 平均孔径/nm 11.008 6.014 5.704 5.714 总孔体积/(cm3/g) 0.013 0.005 0.004 0.003 表 4 MIPs和NIP的吸附量、印迹因子及分配系数
Table 4. Adsorption capacity, imprinting factors, and partition coefficients of MIPs and NIP
分子印迹聚合物 模板分子类型 Q/(mg/g) IF KD/(g/mL) MIP1 胆固醇 0.602 2 2.278 5 0.155 7 MIP2 去氧胆酸 0.718 3 2.717 7 0.191 0 MIP3 β-谷固醇 0.734 7 2.779 8 0.208 1 NIP 0.264 3 0.056 5 表 5 MIPs和NIP的准一级和准二级动力学参数
Table 5. Pseudo-first-order and pseudo-second-order kinetics parameters of MIPs and NIP
分子印迹聚合物 方程 R2 K Qf/(mg/g) MIP1 准一级动力学方程 0.892 0.104 0.617 准二级动力学方程 0.999 0.301 0.645 MIP2 准一级动力学方程 0.933 0.157 0.697 准二级动力学方程 0.998 0.366 0.689 MIP3 准一级动力学方程 0.967 0.169 0.707 准二级动力学方程 0.999 0.426 0.717 NIP 准一级动力学方程 0.303 0.269 0.339 准二级动力学方程 0.998 0.588 0.358 表 6 MIPs和NIP的Scatchard、Freundlich、Langmuir模型方程
Table 6. Scatchard, Freundlich, and Langmuir models for MIPs and NIP
模型 参数 MIP1 MIP2 MIP3 NIP Freundlich等温模型 R2 0.831 0.822 0.864 0.938 nF 2.309 2.558 2.859 3.233 Kf 0.256 0.334 0.378 0.152 Langmuir等温模型 R2 0.922 0.930 0.929 0.986 Qm/(mg/g) 0.840 0.941 0.933 0.338 KL/(L/mg) 0.368 0.475 0.605 0.709 Scatchard等温模型 R2 MI 0.712 0.999 0.998 0.972 MII 0.967 0.926 0.953 Ks/(L/mg) MI 29.851 5.858 11.616 1.483 MII 0.347 0.074 0.272 Qm/(mg/g) MI 5.054 1.957 2.918 0.343 MII 0.636 0.750 0.744 表 7 MIPs和NIP关于Langmuir方程的RL值
Table 7. RL values of MIPs and NIP in Langmuir equations
C0/(mg/L) RL MIP1 MIP2 MIP3 NIP 1 0.731 0.623 0.678 0.585 3 0.475 0.355 0.413 0.319 5 0.352 0.249 0.297 0.219 7 0.279 0.191 0.231 0.168 9 0.232 0.155 0.189 0.135 11 0.198 0.131 0.161 0.114 -
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