【作者】 史西志；

【导师】 林志新； 张大兵；

【作者基本信息】 上海交通大学 ， 生物化学与分子生物学， 2007， 博士

【摘要】 样品前处理技术一直是食品和饲料中违禁药物残留检测研究的重点和难点,发展简单、高效的样品前处理技术,对违禁药物残留进行选择性富集、纯化,提高检测灵敏度,已成为当前国内外食品安全检测技术的重要发展方向之一。固相萃取(Solid-phase extraction,SPE)和免疫亲和色谱(Immunoaffinity chromatography,IAC)是目前使用最广泛的常规样品前处理技术。然而,前者目标物与吸附剂之间的作用力是非特异性的,限制了其进一步的发展;后者所用填料为抗体,其制备过程繁琐、价格昂贵,需要在低温下保存,这些不利因素严重阻碍了IAC的广泛应用。基于分子印迹聚合物的分子印迹固相萃取(Molecularly imprinted solid phase extraction,MISPE)技术,具有高特异性与高选择性、制备简单、稳定性好和可重复使用等优点,已成为近年来分子印迹技术最具应用前景的一个领域。本文对分子印迹聚合物(Molecularly imprinted polymers,MIPs)的基本原理、研究及应用现状等进行了较为全面的综述,对存在的问题和发展趋势进行了分析和展望。在此基础上,主要针对利血平、氯霉素和氨苄青霉素等食品中主要违禁药物,研制其MIPs纳米结构材料,并在食品安全检测中应用,在以下几个方面取得重要研究结果:1.采用本体聚合法以甲基丙烯酸(MAA)为功能单体合成了利血平特异的MIPs。平衡结合实验结果表明功能单体与模板比例为4:1时合成的MIPs具有最好的印迹效果。进一步通过色谱实验对其选择性能和色谱行为进行评价,发现与对照聚合物(Non-imprinted polymers,NIPs)相比,MIPs对利血平具有更好的选择性能和色谱行为;通过紫外光谱、核磁共振波谱、比表面积分析和色谱等方法,系统研究了模板分子利血平与功能单体之间的自组装过程,证明了利血平-NH-基团中氢质子与功能单体在预聚合溶液中具有较强的相互作用,而且利血平分子中叔胺结构周围的质子也表现出了显著的位移变化,表明叔胺结构在印迹和识别过程中也具有重要的作用;在此基础上,通过对分子印迹固相萃取条件的优化,建立了饲料中利血平快速、准确的提取和检测方法,对饲料中三个浓度水平(0.50,1.00和5.00μg/g)的回收率都超过80%。2.采用水相悬浮聚合法制备了氯霉素特异的分子印迹聚合物微球(Molecularly imprinted polymer microspheres,MIPMs),克服了采用经典本体聚合法获得MIPs后,需经研碎、过筛等处理,才能得到所需粒径的分子印迹聚合物颗粒,而且通常存在得率低、颗粒形状不规则、分散性差和研磨过程中易导致MIPs的分子识别与选择性下降等缺点。结果表明,以甲基丙烯酸N,N-二乙基氨基乙酯(DEAEM)为功能单体,模板分子与功能单体比例为1:4时合成的MIPMs对氯霉素具有较好的特异选择性。通过MISPE比较了MIPMs对氯霉素、甲砜霉素和氟甲砜霉素的特异选择性,结果表明MIPMs对氯霉素表现出最高的特异性(53.1%)。同时通过高效液相色谱实验对MISPE对实际样品的富集和纯化效果进行了研究。结果表明,当牛奶和虾样品中氯霉素浓度为5μg/kg时,其回收率分别为92.7%和84.9%,RSD分别为2.7%和3.4%,样品中的氯霉素获得了显著的分离、纯化效果。进一步将氯霉素MISPE与HPLC-MS/MS相结合,对蜂蜜中氯霉素残留进行定量分析,检测限可达0.1μg/kg,符合目前国家标准中检测限量要求(0.3μg/kg)。3.通过悬浮聚合法,获得了氨苄青霉素特异的MIPMs。结果表明,采用DEAEM作为功能单体,模板分子与功能单体比例为1:8时合成的氨苄青霉素MIPMs具有最好的印迹效果。进一步通过色谱实验对氨苄青霉素及其结构类似物青霉素V、苯唑西林和阿莫西林在MIPMs中的色谱行为和印迹效果进行研究,结果表明,MIPMs对氨苄青霉素具有最好的印迹效果,其印迹因子分别为3.75、3.21、3.08和2.83。紫外光谱分析表明氨苄青霉素与DEAEM在水性溶液中具有较强的选择性相互作用。据此对固相萃取条件进行优化,结果表明采用3 mL 5%乙腈(pH,7.0)作为淋洗液,5 mL甲醇作为洗脱液,该MIPMs能有效的净化和选择性吸附蜂蜜样品中的氨苄青霉素。本论文首次制备出利血平分子印迹聚合物、氯霉素和氨苄青霉素分子印迹聚合物微球,并成功应用于食品和饲料中违禁药物的分离与纯化;同时对相关印迹和识别机理进行了全面、系统的研究,进而建立了快速、灵敏、准确检测食品和饲料中主要违禁药物的新方法。这些研究不仅为分子印迹聚合物在固相萃取方面的实际应用提供了理论指导,也为其它违禁药物分子印迹聚合物的相关基础和应用研究提供了有价值的参考。更多还原

【Abstract】 Nowadays, the abused drugs in foods and feeds have been strictly banned, and the Maximum Residue Limits (MRLs) were legislated. Hence, new technologies for enrichment and purification of drug residues have aroused increasingly interests in future studies. The solid phase extraction (SPE) and immunoaffinity chromatography (IAC) are now widely used. However, generic sorbents for SPE usually lack selectivity, and are easily subject to interference by non-target substances with similar characteristics. Although IAC is capable of differentially adsorbing target analytes, it still has some disadvantages such as lacking stability and high costs of antibody preparation. The molecularly imprinted solid phase extraction (MISPE) possesses the similar selectivity with the immunoaffinity and better stability and simplicity than it. Hence, MISPE has become the one of the most important applications of MIPs and displayed higher selectivity than conventional SPE with respect to the binding of target analytes from complex matrices.In this study, the developments and applications of MISPE were comprehensively introduced. The molecularly imprinted polymers for reserpine, chloramphenicol and ampicillin were all prepared by non-covalent methods, respectively. Furthermore, the characteristics of these polymers were discussed, and the application of polymers in solid phase extraction was investigated.1. The specific molecularly imprinted polymers (MIPs) of reserpine (RES) using methacrylic acid (MAA) as the functional monomer and its derived MISPE cartridges for purification and enrichment in feeds were developed and characterised in this study. Evaluation of the various polymers by binding assays indicated that the optimum ratio of functional monomer to template was 4:1. Furthermore, the selectivity and enrichment capacity of the MIPs were assessed by the chromatographic method, which demonstrated that the MIPs can be used as alternative separation materials for RES isolation in feed samples at three spiked levels of 0.50, 1.00 and 5.00μg/g, with the recoveries above 80%. Combination of BET analysis, NMR and UV-vis spectroscopy for investigation on the imprinting and recognition properties revealed that the strong specific interactions between the functional monomer and RES in the prepolymerization solutions or the aqueous solutions were probably responsible for RES recognition. These data showed that the developed MISPE can be a valuable tool for the clean-up and enrichment of RES from the feeds.2. The majority of MIPs were synthesised by bulk polymerization, with the process of obtaining the appropriate polymeric particles which requires grinding and time-consuming sieving with low yield. This leads to inconvenience and makes the method not feasible for manufacturing uses. Furthermore, the shapes and sizes of the particles are usually irregular, resulting in high pressure and decrease of selectivity. Hence, to increase the feasibility for MIPMs production and applicability in aqueous samples, we prepared the novel MIPMs against CAP for MISPE analysis by aqueous suspension polymerization, with water as the suspension medium to mimic the natural condition of CAP during the course of polymerization for improving the specificity, and to avoid complicated post-treatment procedures after polymerization. The optimum ratio of functional monomer to template for the specific rebinding of CAP was 4:1. The resulting MIPMs for CAP had the ability to specifically adsorb CAP, and the MISPE based on the MIPMs was shown to be applicable for clean-up and preconcentration of trace CAP in milk and shrimp samples with high recoveries of 92.7% and 84.9%, respectively. A fast accurate and selective analytical method using the MISPE for extraction of CAP in combination with HPLC-MS/MS for analysis has been developed, and the detection limit for CAP in honey residue was 0.1μg/kg.3. In this study, the ampicillin (AMPI) molecularly imprinted polymer microspheres (MIPMs), used as the solid-phase extraction (SPE) sorbents, were first synthesized by aqueous suspension polymerization. Evaluation of the imprinted polymers by chromatographic analysis indicated that the optimum type and ratio of functional monomer to the template was DEAEM and 8:1, respectively. Under the optimal SPE conditions, the spiked AMPI in the honey samples was purified and enriched. The recoveries were all above 89% and the HPLC chromatogram of AMPI obtained before and after SPE treatment obviously showed that the matrix interferences could be almost removed by the washing step, thus achieving substantial improvement on sample preparation for further determination.In conclusion, the MIPs of RES and the MIPMs of CAP and AMPI were first synthesized, and were successively applied for preconcentration and clean-up for the major abused drugs in foods and feeds. Furthermore, the imprinting and recognition mechanism were comprehensively and systematically studied, which could provide a valuable reference for the related basic research and application in practical uses of MIPs against other abused drugs. Finally, the novel MISPE for purification and enrichment toward the corresponding drugs in foods and feeds were developed for determination, with satisfactory recoveries and improved sensitivity.更多还原