Picturing bacteria on your phone

US scientists have developed a device that, when attached to a mobile phone, can detect small amounts of Escherichia coli in liquid samples. 

Outbreaks of E. coli poisoning still pose a threat to health, particularly in developing countries. As few as 10 E. coli bacteria can cause serious ill health, so accurate and efficient detection devices are required to identify contaminated food and water. Existing detection devices are often expensive, complex and require large equipment unsuitable for field use.   

There are over five billion mobile phones in the world and over 70% of these are in developing areas. Hongying Zhu and colleagues at the University of California, Los Angeles, developed a device able to take advantage of this abundant technology. Zhu commented that ’our cell phone based platform would be very useful to bring advanced technologies to remote and resource poor locations’ adding that the phone provides ’a ubiquitous platform for conducting advanced micro-analysis wherever cell phones work’. 

The device consists of glass capillary tubes with light emitting diode (LED) lights on either end. E. coli antibodies are fixed to the sides of the capillaries and trap any E. coli present in a liquid sample. Secondary antibodies and quantum dots are then added to the capillaries and these bind to the trapped E. coli, capturing the bacteria in a sandwich complex. The LED lights excite the quantum dots, causing them to emit fluorescent light. The light emission is captured by the phone camera as pictures of the capillaries are taken approximately once a second.   

The team tested the device using water samples and milk and were able to selectively detect low concentrations of E. coli, even in the presence of other bacteria species.    

Sunil Arya, an expert in bioanalytical devices at the University of South Florida, US, says that ’the usefulness of the device lies in its applicability to other pathogens of interest through the use of different antibodies to screen water and food samples in remote areas’.    

In the future, Zhu intends to develop the device so a single phone could be used to detect different bacteria.    

Harriet Brewerton