Magnetic resonance imaging (MRI) is an increasingly popular non-invasive technique for diagnosis
and, importantly, does not use harmful radiation. Some tissues show a
natural contrast on MRI, but for some specific types of imaging,
patients are administered a MRI contrast agent to enhance the difference
between the target area and the rest of the body.
A research team led by CHEON Jinwoo at the Center for Nanomedicine,
within the Institute for Basic Science (IBS), developed the Nano MRI
Lamp: A new technology platform that tunes the magnetic resonance
imaging (MRI) signals "ON" only in the presence of the targeted disease.
Published in Nature Materials
, this study can overcome the limitations of existing MRI contrast agents.
‘The Nano MRI Lamp is a new technology platform that tunes the magnetic resonance imaging (MRI) signals "ON" only in the presence of the targeted disease.’
"Typical MRI contrast
agents, like gadolinium, are injected in an "ON" state and distributed
across the whole biological system with relatively large background
signal," explains Director Cheon. "We found a new principle to switch
the MRI contrast agent "ON" only in the location of the target." IBS
scientists discovered how to switch the signal ON/OFF by using the Nano
The Nano MRI Lamp technology consists of two magnetic materials: A
quencher (magnetic nanoparticle) and an enhancer (MRI contrast agent).
The switch is due to the distance between the two. When the two
materials are at a critical distance, farther than seven nanometers (nm),
the MRI signal is "ON", whereas when they are placed closer than seven nm,
the MRI signal is "OFF". The researchers named this phenomenon Magnetic
REsonance Tuning (MRET), which is analogous to the powerful optical
sensing technique called Fluorescence Resonance Energy Transfer (FRET).
The researchers tested the Nano MRI Lamp for cancer diagnosis. They
detected the presence of an enzyme that can induce tumor metastasis,
MMP-2 (matrix metalloproteinase-2) in mice with cancer. They connected
the two magnetic materials with a linker that is naturally cleaved by
MMP-2. Since the linker keeps the two materials close to each other, the
MRI signal was "OFF". However, in the presence of the cancer, the
linker is cleaved by MMP-2, which cause the two materials to be
separated and the MRI signal switched "ON". Therefore, the MRI signal
indicated the location of MMP-2, and the tumor. The scientists also
found that the brightness of the MRI signal correlates with the
concentration of MMP-2 in the cancerous tissue.
Most importantly, the Nano MRI Lamp remains switched off until it
meets a biomarker associated with a specific disease, allowing higher
sensitivity. "The current contrast agent is like using a flashlight
during a sunny day: Its effect is limited. Instead, this new technology
is like using a flash light at night and therefore more useful,"
Beyond cancer diagnosis, the Nano MRI Lamp can, in principle, be
applied to investigate a variety of biological events, such as
enzymolysis, pH variation, protein-protein interactions, etc. IBS
scientists expect that it would be useful for both in vitro and in vivo
"Although we still have a long way to go, we established the
principle and believe that the MRET and Nano MRI Lamp can serve as a
novel sensing principle to augment the exploration of a wide range of
biological systems," concludes Cheon. The research group is now working
on developing safer and smarter multitasking contrast agents, which can
simultaneously record and interpret multiple biological targets, and
eventually allow a better understanding of biological processes and
accurate diagnosis of diseases.