July 28, 2010

US researchers develop new chip application to detect E. coli

A series of "lab on a chip" applications in development at the University of Arizona can identify pathogens in minutes rather than days, using a simple device (which may be attached to a faucet) that can deliver results locally.

Detecting water and foodborne contaminants usually involves collecting a sample, sending it to a laboratory and waiting for it to be filtered, incubated, tested and identified under a microscope. If a critical infection is suspected for E. coli, for example, the pathogen may already have multiplied and spread before the report arrives days later.

The degree of accuracy is three orders of magnitude greater than for conventional real-time or rapid tests, according to reports, and the method can be used to test lower concentrations of pathogens.

Invented by chemical and electrical engineers in the late 1990s, the lab on a chip (LOC) concept is based on the integrated circuit, where encapsulated wires and circuits are integrated into a semi-conductor chip with electricity flowing through it.

The LOC is a small glass laboratory slide filled with nanoparticles that adhere to pathogens applied in a sample drop of water.

Researchers use micro and nanoparticles from 1,000 nanometres down to 10 nanometres to scatter light and strengthen sensitivity. Then combine them with antibodies to the target pathogens, leading to particle agglutination and changing the scattering signal.

The researchers have designed a test that can detect pathogens-E. coli and potentially Cryptosporidium-in drinking water networks, irrigation systems, or wastewater recycling facilities.

The prototype is finished but researchers are now devising different ways to attach the test to water systems, manipulate the nanoparticles and read and deliver the results by computer.