Researchers from Cornell University have developed a miniaturised DNA-based biological testing system that fits on a silicon chip and can be customised to detect a wide variety of microorganisms.
The chip consists of two areas, the first of which captures DNA from the sample and purifies it. The second is a reaction chamber where a polymerase process chain reaction is performed to rapidly replicate the selected segment of DNA, which can then be tested.
‘Other people have developed real-time PCR on silicon chips, but nobody has really done the purification of the DNA sample on the same chip,’ says Nathan Cady, one of the researchers on the study. ‘As near as we can tell, we are one of the first groups to incorporate the purification step into the chip.’
Cady and his colleagues are currently working on incorporating a third step to the process that uses fluorescence technology where an added dye would glow green to indicate a positive sample.
The chip itself is 2 cm x 4 cm in size. Because PCR requires a precise series of specific temperatures at specific times, it fits into a tiny device (5 cm x 5 cm x 3 cm) that handles the cycling of the temperature. Once they have finally incorporated the fluorescence, Cady expects they will have a device roughly the size of a shoebox that will be capable of real-time automated detection of biological agents.
‘Part of the reason we put these functions on a chip is that it simplifies the process,’ says Cady. ‘You can hand this to someone in the field, someone who is not a trained lab technician, and they can do it.’
Another advantage of this system is that it has a very broad range in what organisms it can be used to detect. According to a statement from Cornell, that makes it very useful for a variety of purposes from monitoring food and water supplies to detecting agents of biological warfare.
‘We can detect pretty much any organism as long as we have the PCR primers for it,’ said Cady.