The study explaining that simple smartphone based method for detecting extremely low levels of norovirus; as norovirus the highly infectious microbe that causes about 20 million cases of food poisoning in the United States each year goes a long way. Just 10 particles of the virus can cause illness in humans. Advancing in rapid monitoring of human viruses in water are essential for protecting public health.
This rapid, low-cost water quality monitoring technology could be a transformational tool for reducing both local and global disease burdens. Devices to detect norovirus in small quantities do already exist, but they typically require a laboratory setting with an array of microscopes, lasers and spectrometers that can cost thousands of dollars.
To detect norovirus in the field, such as on cruise ships or in municipal water wells, the team decided to use much simpler materials; paper, in the form of microfluidic chips, and a smartphone. Paper substrate is very cheap and easy to store, and we can fabricate these chips easily. The fibrous structure of paper also allows liquid to flow spontaneously without using the pumping systems other chips, such as silicon chips, usually require
Smartphone based method
However, scientists usually detect contaminants on the chips by measuring the scattering and reflection of light in a sample; and paper’s porousness and opacity can cause background scattering that interferes with imaging and makes it difficult to detect very small concentrations of a virus. So, the group developed a new way to detect norovirus; by counting fluorescent beads rather than measuring light intensity.
The process starts with adding potentially contaminated water to one end of a paper microfluidic chip. To the other end, a tester adds tiny; fluorescent polystyrene beads (picture the little white balls inside of a bean bag – these are the same material, but much smaller). Each bead is attached to an antibody against norovirus. If norovirus is present, several of the antibodies attach to each virus particle, creating a little clump of fluorescent beads.
Contaminants on the chips
Norovirus particles are too small to be imaged by a smartphone microscope, and so are antibodies; But when you have two or three or more of these beads joined together; that indicates that the norovirus is there, causing the beads to aggregate. These clumps of beads are large enough for a smartphone microscope to detect and photograph.
Then, a smartphone app the researchers created counts; the number of illuminated pixels in the image to identify the number of aggregated beads, and subsequently; the number of norovirus particles in the sample. That’s another advantage of the paper chip; Through capillary action, the groups of beads spread out along the paper, making them easier to count.