By extending MRI to such fine resolution, the scientists have created a
microscope that, with further development, may be powerful enough to unravel the
structure and interactions of proteins, paving the way for advances in
personalized healthcare and targeted medicine.
"This technology stands to revolutionize the way we look at viruses, bacteria, proteins, and other biological elements," said IBM Fellow Mark Dean, vice president of strategy and operations for IBM Research.
The technique used is called magnetic resonance force microscopy (MRFM), which relies on detecting ultrasmall magnetic forces. In addition to its high resolution, the imaging technique has the further advantages that it is chemically specific, can "see" below surfaces and, unlike electron microscopy, is non-destructive to sensitive biological materials.
The IBM-led team has significantly boosted the sensitivity of MRFM and combined it with an advanced 3D image reconstruction technique, allowing them to pioneering use of MRI on nanometer-scale biological objects.
The technique was applied to a sample of tobacco mosaic virus and achieved resolution down to four nanometers. One nanometer (nm) is one billionth of a meter; a tobacco mosaic virus is 18 nm across.
"MRI is well known as a powerful tool for medical imaging, but its capability for microscopy has always been very limited," said Dan Rugar, manager of nanoscale studies, IBM Research.
"Our hope is that nano MRI will eventually allow us to directly image the internal structure of individual protein molecules and molecular complexes, which is key to understanding biological function."
The new device does not work like a conventional MRI scanner, which uses gradient and imaging coils. Instead, the researchers use MRFM to detect tiny magnetic forces as the sample sits on a microscopic cantilever – essentially a tiny sliver of silicon shaped like a diving board.
Laser interferometry tracks the motion of the cantilever, which vibrates slightly as magnetic spins in the hydrogen atoms of the sample interact with a nearby nanoscopic magnetic tip. The tip is scanned in three dimensions and the cantilever vibrations are analyzed to create a 3D image.
Click here to view a flickr album of photos taken using the new technique.
Photos with explanations can also be viewed at IBM NanoMRI of virus particles - 1 and IBM NanoMRI of virus particles - 2 and IBM Cantilever end with virus sample and IBM NanoMRI and IBM NanoMRI closeup and IBM MRFM setup.
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