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Bacteria are omnipresent. They can be found in food, water, living beings, and in the surrounding environment, being ubiquitous in Nature. Although many bacteria strains are nonpathogenic, several are hazardous to health, causing different health complications. Escherichia coli (E. coli) bacteria, existing in contaminated food and water, have been identified as the main cause of several health outbreaks. In order to prevent disease outbreaks, it is crucial a rapid and real-time detection of E. coli present in contaminated food and water, which is a prerequisite to the food industry. A novel methodology proposed in the present work demonstrates a basic microfluidics system composed of a glass double-chambered cell with an activated surface for E. coli detection. Anti-E. coli antibodies are immobilized on the glass surface through a complex functionalization procedure. During this process, dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP) is used to induce an homeotropic alignment of the nematic liquid crystal molecules. These functionalized glass surfaces in contact with analyte samples will allow the formation of immunocomplexes by the binding of E. coli bacteria to the anti-E. coli antibodies, if present. To detect the presence of E. coli bacteria, the immunosensor cell is then filled with a nematic liquid crystal. Using two crossed polarizers, in order to visualize the interaction of the incident light with the liquid crystal, it was possible to observe the results. Different methodologies to interpret the results, such as the quantification of the bacteria, are also discussed. Besides the food industry, these immunosensors can also be used in a large number of point-of-care health applications, even in regions without electrical energy and healthcare means.
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