基于3D打印标样制备LA-ICP-MS原位分析富硒食品

The laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) hyphenate technique was applied in many fields with its prominent advantages such as: high spatial resolution, high sensitivity and sample throughput, multielement capability and direct analysis of solid sample. It is a modern and powerful analytical tool for the mapping of elemental distribution in samples. The "bottleneck" problem of the extreme lack of standard sample has hampered its application and development. Therefore, the concept of 3 dimension fast printing quasi-sample standard is presented. Printing materials is chosen and blended. Preparation for standard sample with overall matrix-matched is accelerated. The basic theories of fractionation effect、matrix effect、external calibration、 internal standard calibration and isotope dilution calibration for the determination of 3D printing standard by LA-ICP-MS were completely investigated. The imaging interesting elements in the cross-section、microsquare and entire selenium-enriched food were separately analysed. Those relative information about interesting element content、 isotope ratio and their metallomics between selenium-enriched food and non selenium-enriched food were epurated and analysed. The analytical performance for element fractional distribution from cross-section、microsquare to entire one were evaluated by multi-information amalgamation. A new standard detect method for in situ、real time、fast analysis of selenium-enriched food will be successfully developed. Scientific distinction for the natural selenium-enriched food or the mock one was resolved. Following, Selenium speciation analysis in Enshi selenium-enriched food will be deep studied. Reference criterion matter for the selenium speciation analysis will be added. The new choice for direct screening biological activies of selenium will be offered.

LA-ICP-MS技术以其高的空间分辨率、灵敏度、多元素同时检测、固体样品直接分析等优势，是样品中元素分布作图显像分析强有力的工具。得到了广泛应用，但阻碍其应用发展的“瓶颈”问题是标样的极度缺乏。项目提出三维(3D) 快速打印 “准样品”的标样设想, 选配打印材料，加速基体全面匹配的标样研制并对LA-ICP-MS测定中的分馏效应、基体效应、外标直接校准、内标校准及同位素稀释对比校准等相关基础理论系统研究。藉此，对富硒食品剖面微区到整体的元素成像作图分析，提炼分析富硒与非富硒食品中目标元素的含量及其同位素比值等金属组学信息，多信息融合评价富硒食品剖面及微区到整体元素分布形态的分析性能。最终成功建立富硒食品原位、实时、快速分析检测标准新方法，解决天然富硒食品真假的科学区分问题。深入开展恩施天然富硒食品中硒的化学形态分析研究，增添硒形态分析的参考标准品，为生物活性硒物种的直接筛选提供新选择。

标样缺乏是阻碍LA-ICP-MS应用发展的主要问题之一。项目“基于3D打印标样制备LA-ICP-MS原位分析富硒食品”提出3D打印标样的设想, 建立富硒食品原位、快速分析方法，解决天然富硒食品真假的科学区分问题。开展恩施天然富硒食品中硒的化学形态分析，为生物活性硒物种的筛选提供参考选择。. 采用甲基丙烯酸单体、低聚物和光引发剂混合树脂，优化硒标配方，3D打印制备出玉米、大豆等固体标样，增加了LA-ICP-MS分析的标样制备方法。打印的标样用于校准基本成线性，相关系数R >= 0.98。打印标样的精密度（RSD＜15%）尚需提高。. 市场上一般会使用硒酸钠添加掺假，对于玉米、大豆等天然富硒食品真假的区分，先用0.01摩尔的稀硝酸浸泡1.50-2.50克食品，搅拌清洗提取3-5分钟，提取液用ICP-MS测试，若检测出硒信号，外标法校准给出量值，不能判断为原始富硒食品，掺假嫌疑重大。若无硒信号检出，把对应食品颗粒纵向剖开，直接用激光剥蚀种皮、胚乳、胚等微区。若三个轮廓空间均无硒信号，则判断此种食品为非富硒食物；若出现种皮硒信号最低、胚乳居中、胚微区最高，且胚中剥蚀出的硒COUNTS高于1.0μg/g标样的信号强度，则判定为天然富硒食品。外标法校准硒含量，通过种皮、胚乳、胚在整颗粒中的质量比例，算出每粒食品中的硒含量。. 对野生超硒植物遏蓝菜中硒形态分析，得到分子量在30kD左右的蛋白，可能为一个磷酸核酮糖羧化酶硒蛋白，硒以硒代蛋氨酸进入到蛋白质中，具体键合结构序列待剖析证实。以毛细管扎针取鲜叶汁直接电喷雾进到高分辨LC-MS，正扫描其质谱图，分析一级和二级质谱图，推测出裂解过程，原位分析出硒代蛋氨酸(SeMet)。对比研究无土栽培的遏蓝菜叶片，分析出SeMet，与野生样分析结果一致，说明遏蓝菜富硒主要以SeMet形态富集。. 以壳聚糖Chitosan作壁材、SeMet为模型控制物，制备SeMet@CS复合纳米微球。载药量和包封率分别为0.54%和31.94%，体外缓释硒的性能良好，对人乳腺MCF-7癌细胞的生长抑制率随缓释时间延长而增加。避免了突释效应，实现硒剂量的缓释调控，作为硒化药物或强化剂可应用于医药、营养补品等行业。