Paper-based biosensor
[1] However, there are also limitations to these assays, and scientists are continually working to improve accuracy, sensitivity, and ability to test for multiple contaminants at the same time.
This causes the cells to lyse and release the β-galactosidase enzyme, which triggers the conversion of the substrate into a fluorescent product, indicative of the presence of the pathogen.
The device was found to be highly specific to E. coli, and was tested against the presence of Enterobacter cloacae, Aeromonas hydrophila, and Salmonella Typhimurium.
The bacterial cells will then move up the paper via capillary action, and once it reaches the reaction zone, it reacts with the reagents to produce a pink to red color.
These strips are a form of lateral flow assay, where the test line is composed of fluorescence antibody-labeled CdSe/ZnS quantum dots (Ab-QDs) as probes.
When no Salmonella is present, the Ab-QDs function as the donor, with graphene being the acceptor, and the fluorescence of the test line is quenched by this energy transfer.
[13] Per World Health Organization (WHO) standards, for water to be considered clean enough for drinking, bacteria should be undetectable in any 100 mL sample.
The primary contaminants of water are pathogens, such as the bacteria Campylobacter, Clostridium, Salmonella, Staphylococcous, Anabaena, Microcystis, worms such as Schistosoma mansoni, and Taenia saginata, protozoans such as Entamoeba histolytica and Giardia duodenalis, and viruses and fungi such as enteroviruses and microsporidia.
Outbreaks of waterborne diseases, such as cholera, have affected millions in the 19th and 20th centuries over the course of several pandemics, usually as a result of inadequate wastewater treatment systems and general sanitation.
[14] Cholera is just one example of waterborne disease, however, and more broadly, 780 million people worldwide still lack access to clean drinking water.
[15] They can also be time consuming, for example, microbiological assays necessitate growing and isolating the pathogen from the sample, which can take several days or even weeks, in addition to preparing media.
[1][3] In general, settings with limited resources could benefit from low-cost, easy to use, on-site, and rapid testing of water samples.
This introduces limitations regarding the handling of complex chemical compounds or managing multistep assays, depending on the biosensor in question.
