A group of scientists at Rice University has devised a way to use iron in MRI contrast agents that are less toxic than gadolinium – and work twice as well.
The process, described in a recent report published in ACS Nano, involves the insertion of ferrous molecules into nanoparticles known as nanomatryoshka particles. These particles consist of a microscopic sphere, surrounded by a shell (hence the reference to Russian nesting dolls). By manipulating the shape of the inner particle, scientists can modify the resonance frequency and how well it can absorb and respond to magnetic fields.
The nanomatryoshka particles used in the current research were engineered in the late 1990s by lead researcher Naomi J. Halas, head of Rice University’s Laboratory for Nanophotonics. These microscopic particles have layers of varying thickness, which are made up of conductive metal and silica.
Earlier research found that it was possible to embed a certain amount of gadolinium chelates into the silica layers. The Rice University team were able to embed four times the amount of iron into the layers, resulting in a 100 percent improvement in performance. An outer shell made from gold prevents the chelates from leaching out, a problem that often causes degradation of the signal that provides an image – and in the case of gadolinium, results in toxicity as these enter the bloodstream.
This news comes at a time when the issue of gadolinium toxicity has raised concerns in the medical community. In a press release, Halas said, “The possibility of eliminating gadolinium exposure and getting a two-fold improvement in T1 MRI contrast performance is going to intrigue radiologists. When they hear we’ve done this with iron I expect they will be very surprised.” T1 MRI scans, which typically use gadolinium-based contrast agents (GBCAs), produce brighter images than lower-definition T2 scans. Iron-based contrast agents have long been used for the latter, but until now, there have been few alternatives to GBCAs for the former.
Gadolinium-based contrast agents have been known to cause serious health problems in patients with kidney disease. However, for the past decade, these injuries have been appearing in patients who had normal kidney function at the time they underwent their MRI scans.
Certain types of GBCAs release small amounts of toxic gadolinium into the bloodstream, resulting in a condition known as Nephrogenic Systemic Fibrosis. Symptoms, which include severe pain in the extremities, headaches, and impaired cognitive function, can appear within minutes following an MRI. These injuries are now a cause of action in a growing number of lawsuits currently being filed against drug manufacturers who failed to warn patients and their doctors of the possible side effects of gadolinium.
In small amounts, iron is not only harmless, but it is also a necessary nutrient that plays a vital role in the production of red blood cells and the transfer of oxygen from the lungs to the tissues. It is also less expensive than gadolinium. Thanks to the work of Dr. Halas and her colleagues, radiologists will soon have a safer and more economical alternative to toxic GBCAs.