Gunda Naga Siva Kumar, Dasgupta Saumyadeb, Mitra Sushanta K
Micro & Nano-scale Transport Laboratory, Lassonde School of Engineering, York University, Toronto, M3J 1P3, Ontario, Canada.
PLoS One. 2017 Sep 6;12(9):e0183234. doi: 10.1371/journal.pone.0183234. eCollection 2017.
We have developed a new litmus paper test (DipTest) for detecting Escherichia coli (E. coli) in water samples by performing enzymatic reactions directly on the porous paper substrate. The paper strip consists of a long narrow piece of cellulose blotting paper coated with chemoattractant (at bottom edge), wax hydrophobic barrier (at the top edge), and custom formulated chemical reagents (at reaction zone immediately below the wax hydrophobic barrier). When the paper strip is dipped in water, E. coli in the water sample is attracted toward the paper strip due to a chemotaxic mechanism followed by the ascent along the paper strip toward the reaction zone due to a capillary wicking mechanism, and finally the capillary motion is arrested at the top edge of the paper strip by the hydrophobic barrier. The E. coli concentrated at the reaction zone of the paper strip will react with custom formulated chemical reagents to produce a pinkish-red color. Such a color change on the paper strip when dipped into water samples indicates the presence of E. coli contamination in potable water. The performance of the DipTest device has been checked with different known concentrations of E. coli contaminated water samples using different dip and wait times. The DipTest device has also been tested with different interfering bacteria and chemical contaminants. It has been observed that the different interfering contaminants do not have any impact on the DipTest, and it can become a potential solution for screening water samples for E. coli contamination at the point of source.
我们开发了一种新的石蕊试纸测试法（浸试法），通过直接在多孔纸质底物上进行酶促反应来检测水样中的大肠杆菌。试纸条由一条狭长的纤维素吸水纸组成，在底部边缘涂有化学引诱剂，顶部边缘涂有蜡质疏水屏障，在蜡质疏水屏障正下方的反应区涂有定制配方的化学试剂。当试纸条浸入水中时，水样中的大肠杆菌由于趋化机制被吸引到试纸条上，随后由于毛细作用机制沿试纸条向上移动到反应区，最终毛细作用在试纸条顶部边缘被疏水屏障阻止。聚集在试纸条反应区的大肠杆菌会与定制配方的化学试剂发生反应，产生粉红色。将试纸条浸入水样中时出现的这种颜色变化表明饮用水中存在大肠杆菌污染。浸试法装置的性能已通过使用不同的浸入和等待时间，对不同已知浓度的大肠杆菌污染水样进行了检测。浸试法装置也已针对不同的干扰细菌和化学污染物进行了测试。据观察，不同的干扰污染物对浸试法没有任何影响，它有可能成为在水源处筛查水样中大肠杆菌污染的一种解决方案。
