Research done by a group under Kenneth Watkin, a professor at the University of Illinois at Urbana-Champaign, revealed a novel way to package gadolinium molecules for use in medical imaging. In addition, it appears that the new form of an old contrast agent has some very interesting properties:
The tiny carriers Watkin and McDonald are proposing would, in effect, zero in on tumors in much the same way that smart bombs take aim at strategic targets.
Watkin’s transport system of choice are nanoparticles of gadolinium oxide…
In their work with gadolinium oxide nanoparticles, Watkin and McDonald started by breaking nanoparticles down into even smaller particles. Next, they successfully coated the particles with dextran, a naturally occurring carbohydrate.
The chemical coating – which Watkin compares to the thin, outer shell of an M&M candy – functions as a spacer, preventing the nanoparticle from undergoing a chemical reaction when it comes in contact with water. It also keeps the nanoparticles from clumping and behaving erratically.
“The M&M analogy is really a great one because it says you can put things on the outside and you can have something on the inside,” Watkin said. “And in the case of gadolinium oxide, it’s really a metallic ion.”
Watkin said gadolinium oxide is a superb imaging agent because of its superparamagnetic properties – “meaning that they work well within a magnetic resonance imaging machine.”
Its properties as an effective emitter of radiation sources also make it well-suited for use with a type of cancer therapy called neutron capture therapy.
“What it means,” Watkin said, “is that these little particles capture the neutrons and emit alpha and gamma rays, and that energy – sent out from an accelerator – is what can be used to kill cancer cells.
“In looking at this, we both said, ‘Holy … cow!’ These little gadolinium particles capture neutrons at four times a greater rate than boron, and yet boron is what is (currently) used for neutron capture. This means it (gadolinium oxide) is potentially a multimodal agent” …in other words, “a contrast agent that would work with a number of different medical imaging techniques.”
Among the most promising applications for using gadolinium oxide nanoparticles as a neutron capture therapy agent is in the treatment of brain tumors.
“Treating brain tumors – typically called glioblastomas – is very difficult,” Watkin said. “Irradiating them is really difficult because you alter all kinds of tissues in the brain. And getting little bubbles like this or other kinds of contrast agents into the brain is difficult because the holes that allow plasma and other substances to flow through the brain are very small – about 25 nanometers. With such a small opening, you’ve got to have something pretty tiny to get in there. So these little gadolinium oxide particles can be really useful.”