Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Medical imaging relaxes to brighten up

09.04.2002


Protein packaging may enhance MRI contrast.



Images of body tissues and organs could soon be brighter and sharper thanks to a technique developed by Italian chemists. They have made the chemical contrast agents used in magnetic resonance imaging (MRI) produce a stronger signal by trapping them in protein cages just 12 millionths of a millimetre (nanometres) or so widesup>1.

Such improvements increase the contrast of the images, so they should reveal more detailed information, enabling doctors to better discriminate between different tissue types. The researchers, Silvio Aime and co-workers at the University of Turin, hope to persuade their protein cages to latch onto particular cells, as this would help them to pinpoint diseased tissues.


One of the best MRI contrast agents is a molecule containing atoms of the element gadolinium. Injected into the bloodstream, the gadolinium compound accumulates in abnormal tissues such as scar tissue and tumours, so they become brighter in MRI scans. The agent is ultimately passed out of the body in urine.

Making gadolinium contrast agents brighter is a subtle business. Gadolinium enhances MRI contrast because it helps water molecules to relax. The MRI signal comes from water molecules that have been stimulated into an excited state by radio waves. The quicker the water molecules return to their normal state, the stronger the signal. Gadolinium assists in this process.

How well gadolinium does its job depends on the molecules around it. Proteins can amplify the relaxation induced by gadolinium because chemicals on their surface interact with water molecules. Aime’s team found they got better MRI contrast by keeping standard gadolinium contrast agents close to proteins.

Nature provided them with a ready-made protein cage in the form of ferritin, a shell of 24 protein molecules with a cavity about 7.5 nanometres across. Liver cells store iron inside ferritin, packing up to 4,500 iron atoms into its hollow interior.

The Italian team used a stripped-down version of ferritin known as apoferritin. They trapped the gadolinium contrast agent inside the cavity by first splitting the capsule open in acid and then reforming it in neutral solution containing the gadolinium compound. Each apoferritin compartment holds about ten of these gadolinium molecules.

Crucially, apoferritin’s walls are riddled with channels that are wide enough to let water in and out but too narrow to let gadolinium through. This exchange of water between the inside and the outside is essential for increasing its relaxation rate. Apoferritin seems to enhance gadolinium’s relaxation about 20-fold, the team reports.

They haven’t yet discovered how this translates into changes in MRI contrast, however. The clinical usefulness of the new approach will depend on many other factors, such as how efficiently apoferritin-bound gadolinium can be transported round the body, and how easily it can be cleared from the bloodstream.

References
  1. Aime, S., Frullano, L. & Crich, S.G. Compartmentalization of a gadolinium complex in the apoferritin cavity: a route to obtain high relaxivity contrast agents for mangetic resonance imaging. Angewandte Chemie International Edition, 41, 1017 - 1019, (2002).


PHILIP BALL | © Nature News Service

More articles from Health and Medicine:

nachricht Laser activated gold pyramids could deliver drugs, DNA into cells without harm
24.03.2017 | Harvard John A. Paulson School of Engineering and Applied Sciences

nachricht What does congenital Zika syndrome look like?
24.03.2017 | University of California - San Diego

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>