Miniaturised scanner zooms in on disease

Tag : Chemical Concentrates

A handheld nuclear magnetic resonance (NMR) scanner that candiagnose diseases and identify pathogens has been built byscientists in the US.
The revolutionary scanner is many times smaller than conventionalNMR spectroscopy machines, which require huge magnets to create thepowerful magnetic fields necessary to make them work.
Nuclear magnetic resonance spectroscopy works by lining up nucleiin a sample using a powerful magnetic field and then zapping themwith radio waves that cause them to wobble, or precess.
This precession induces currents in a nearby coil which can be usedto determine the chemical structure of the molecules that containthe nuclei. The same process is used in magnetic resonance imagingmachines to make non-invasive images of human bodies. The newdevice does not produce images, however. Weaker fields
In conventional NMR spectroscopy machines, powerful fields arenecessary to line up individual nuclei.
However, Ralph Weissleder at Harvard Medical School in Cambridge, Massachusetts, US, andcolleagues have found that magnetic nanoparticles generate a muchlarger signal than single nuclei, and can thus be detected usingthe weaker fields from small permanent magnets.
The trick that Weissleder and colleagues have perfected is to coatthese nanoparticles with molecules that bind to specificbiomolecules, or bacteria and viruses.
This binding process causes the nanoparticles to clump together,producing a measurable change in the signal they produce. In thisway, the team says it can identify a large variety of biologicaltargets.
The team has squeezed the electronics that detect and interpret thesignals onto a chip just 2 millimetres square (pdf format). Small and sensitive
What's more, the researchers have also designed a microfluidicsnetwork that shuttles the samples around and concentrates them involumes of just five millionths of a litre (5 microlitres)  some60 times less than conventional systems.
"The smaller the system, the better the sensitivity in terms ofabsolute amount of sample that can be detected," says Hakho Lee,lead author on the research.
The prototype device has eight tiny coils, each of which canmonitor nanoparticles sensitive to different biomolecules. Futuredevices could employ many more such coils.
The result is a prototype machine that is 800 times more sensitivethan standard NMR scanners used in many laboratories, saysWeissleder.
The team put the prototype through its paces, showing that it issensitive enough to detect just 10 bacteria in a given sample. Byloading each of the eight microcoils with different nanoparticles,the system could distinguish between simulated blood samplesrepresenting healthy individuals, those with cancer, and those withdiabetes, by looking for eight different biomarker molecules. Multiple applications
"The biggest advantage is that we don't need sample preparation orpurification steps," Lee says. The nanoparticles are simply addedto whatever samples are present. "This method could provide an easyand fast way to diagnose almost any kind of disease, such asbacterial infection or cancers in point-of-care settings  rightnext to the patient or in developing countries."
The device could also be used to test for water purity or evenapplied to gaseous samples, to search for airborne pathogens orpollutants.
Other researchers are impressed with the work. "If you came to mylab you would see that our spectrometers occupy whole rooms, and weare always struggling with sensitivity in NMR experiments," says Dusan Uhrin , an NMR spectroscopist at the University of Edinburgh.
"They have been able to improve the sensitivity such that they candetect just a few bacteria. It's quite remarkable that they candetect down to that limit," he says.
Weissleder has filed a patent for the design and started a companycalled T2 Biosystems to market the devices.
Journal reference: Nature Medicine (DOI: 10.1038/nm.1711)