Ganz Kyle R, Clime Liviu, Farber Jeffrey M, Corneau Nathalie, Veres Teodor, Dixon Brent R
Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada.
Life Sciences Division, National Research Council Canada, Boucherville, Quebec, Canada.
Appl Environ Microbiol. 2015 Jun 15;81(12):3925-33. doi: 10.1128/AEM.03868-14. Epub 2015 Apr 3.
The sensitivity and specificity of current Giardia cyst detection methods for foods are largely determined by the effectiveness of the elution, separation, and concentration methods used. The aim of these methods is to produce a final suspension with an adequate concentration of Giardia cysts for detection and a low concentration of interfering food debris. In the present study, a microfluidic device, which makes use of inertial separation, was designed and fabricated for the separation of Giardia cysts. A cyclical pumping platform and protocol was developed to concentrate 10-ml suspensions down to less than 1 ml. Tests involving Giardia duodenalis cysts and 1.90-μm microbeads in pure suspensions demonstrated the specificity of the microfluidic chip for cysts over smaller nonspecific particles. As the suspension cycled through the chip, a large number of beads were removed (70%) and the majority of the cysts were concentrated (82%). Subsequently, the microfluidic inertial separation chip was integrated into a method for the detection of G. duodenalis cysts from lettuce samples. The method greatly reduced the concentration of background debris in the final suspensions (10-fold reduction) in comparison to that obtained by a conventional method. The method also recovered an average of 68.4% of cysts from 25-g lettuce samples and had a limit of detection (LOD) of 38 cysts. While the recovery of cysts by inertial separation was slightly lower, and the LOD slightly higher, than with the conventional method, the sample analysis time was greatly reduced, as there were far fewer background food particles interfering with the detection of cysts by immunofluorescence microscopy.
当前用于食品中贾第鞭毛虫囊肿检测方法的灵敏度和特异性在很大程度上取决于所使用的洗脱、分离和浓缩方法的有效性。这些方法的目的是产生一种最终悬浮液，其中含有足够浓度的贾第鞭毛虫囊肿用于检测，且干扰性食物残渣的浓度较低。在本研究中，设计并制造了一种利用惯性分离的微流控装置用于分离贾第鞭毛虫囊肿。开发了一种循环泵送平台和方案，将10毫升悬浮液浓缩至不到1毫升。在纯悬浮液中对十二指肠贾第鞭毛虫囊肿和1.90微米微珠进行的测试证明了微流控芯片对囊肿相对于较小非特异性颗粒的特异性。当悬浮液循环通过芯片时，大量微珠被去除（70%），大多数囊肿被浓缩（82%）。随后，将微流控惯性分离芯片集成到一种从生菜样品中检测十二指肠贾第鞭毛虫囊肿的方法中。与传统方法相比，该方法大大降低了最终悬浮液中背景残渣的浓度（降低了10倍）。该方法还从25克生菜样品中平均回收了68.4%的囊肿，检测限（LOD）为38个囊肿。虽然通过惯性分离回收囊肿的效率略低于传统方法，检测限略高于传统方法，但由于干扰免疫荧光显微镜检测囊肿的背景食物颗粒少得多，样品分析时间大大缩短。
