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Alpha-Screen (αScreen) Fast and Cheap Bacteria Detection

Monika Weber, Christopher Yerino, Hazael Montanaro, Kane Siu Lung Lo, and Mark Reed, Yale University, New Haven, CT

Every year, food-borne bacteria cause thousands of infections in humans and animals. Outbreaks of E.Coli and Salmonella commonly occur in meat, vegetables, and processed food products. The most recent and deadliest recorded E.Coli outbreak caused 39 deaths and over 3,500 reported cases of poisoning in May and June of this year in Germany. An effective method for disease detection and prevention is still missing, mostly due to long incubation times and a high operation cost associated with conventional methods.

altThe most widely used method for bacteria detection, the standard plate count, takes from 24 to 48 hours, due to the time needed for bacteria to grow detectable colonies. This time is too long for most applications in the food industry, especially when food products need to be delivered and sold fresh. Faster methods, including PCR or labeled detection and fluorescent imaging, are too expensive to be widely applied.

altαScreen is a MEMS (microelectromechanical system) rapid pathogen screener for food-borne illnesses. It has the potential to improve health standards at the consumer level by increasing sensitivity, keeping the cost down, and reducing testing time. This technology could allow screening of up to 100% of food produced in food processing plants before it is delivered to the consumer; thus, for the first time, eliminating the risk of infection. αScreen is portable and ready to use in any conditions. It is highly accurate, can detect as low as a single bacteria, is small, fast, and approximately 50 times less expensive than the established, currently used detection methods. αScreen can detect any chosen type of bacteria from whole blood or pre-defined fluid. The device size is less than 1 × 1 × .5", and the cost is as low as $1.00 per test.

αScreen operation is simple. The user injects a sample of blood into the inlet chamber. Further on, the device processes the sample automatically. Using dielectrophoresis, any present bacteria is separated from the large blood components, e.g. red and white blood cells. For bacterial detection, nanoribbon/nanowire field effect transistors are used, which are well explored, label-free nanosensors capable of detecting low concentrations of biomolecules, i.e. disease markers, to provide point-of-care diagnostics. In order to achieve selectivity and specificity of the detection and eliminate false-positive response, the sensors are functionalized with bacteriaspecific antibodies.

altIn the food industry, samples taken with a syringe directly from a piece of meat are tested for bacterial infections to determine if the meat is safe to be delivered to customers. Since the device can test any sample of blood, it is also possible to apply it to medical diagnosis and potentially detect diseases related to post-consumption of food in patients. If modified, αScreen also can be used for vegetable and crop examination. In this case, the vegetable would be washed in water or salt-containing solution, and the bacteria on the vegetable surface would be washed into this liquid. The liquid would then be examined.

αScreen is designed to integrate innovative bacteria separation and demonstrated state-of-the-art detection methods. The whole bacteria separation system has been modeled using the COMSOL Multiphysics software. Subcom ponents for detection have already been successfully prototyped and are currently under testing. The core part of αScreen is a silicon nanoribbon FET sensor fabricated using a CMOS-compatible process using optical photolithography and a microfluidic two-step separator for bacteria separation from the whole blood.

The ultimate goal is the detection of several hundred diseases. It has the potential to revolutionize diagnostics of bacterial diseases.

For more information, visit http://contest.techbriefs.com/component/content/article/1896.