Contrast. It’s not just a setting on the TV – it’s also a critical part of how doctors practice medicine today. Looking inside the body to see what’s going on with x-rays is a 100-year old trick. Everyone knows that x-rays spot broken bones, swallowed toys, and that sometimes, like with a chest x-ray or a mammogram, they can spot cancer. But what happens when you want to see, in really fine detail, something like a blood vessel that may be partially blocked and needs to be fixed? The problem is contrast – most of the body is about the same density, and x-rays have a hard time spotting, say, a blood vessel threading through your liver.
What we do to spot them is make the blood denser – more like bone – by injecting solutions of dense pharmaceuticals called “contrast media”, right into the blood. These molecules float through the bloodstream and make the blood appear on x-rays, and CT scans, for a few minutes after injection. After that, the body removes them naturally. The challenge, though, is that doctors always want better contrast. Better contrast means better diagnosis, and better treatment. A team of chemists and biologists at GE Global Research are working on a way to do just that, using nanotechnology.
It turns out that lots of contrast means lots of atoms. One of the best ways to pack lots of atoms into a really small space is with nanoparticles. These tiny particles are less than one one-thousandth the size of a red blood cell, but each one still packs upwards of 50 contrast generating metal atoms. In contrast (ha!), a similar sized traditional contrast molecule would only carry three to six atoms. The real trick to the particles, though, isn’t just making them, but getting them to behave well enough to be used inside the body.
The team at Global Research is optimizing a handful of parameters to make these contrast particles work. They’ve set the size carefully – in this case making the particles small enough to be removed by the kidneys, but large enough to otherwise remain in the blood (and stay out of other parts of the body). They have also identified a coating to put on the particles, one that is water soluble, and doesn’t stick to other types of cells as it works its way through the blood. Currently, the team is working to ensure biocompatibility, carrying out experiments like mixing the particles with blood cells and observing their reaction. Once optimized, the particles can be pushed forward into the rigorous process of scaleup and clinical trials. To date, the team has had great results, and their work is the subject of a recently published technical document (Chem. Commun., 2010, 46, 8956-8958). We expect more great results from this team as we push the compounds for better and better performance and, in the end, better medicine.