A Single Nanoparticle Enables Two Medical Imaging Techniques

New capability could open up its use for a variety of diagnostic and therapeutic processes

2 min read
A Single Nanoparticle Enables Two Medical Imaging Techniques
Image: Christine Daniloff/MIT

Researchers at the Massachusetts Institute of Technology (MIT) have developed a nanoparticle that enables both magnetic resonance imaging (MRI) as well as fluorescent imaging in living animals.  The researchers believe that a single nanoparticle capable of performing these two functions should be able to help track specific molecules through the body, monitor a tumor’s environment, and determine whether drugs have reached their intended target.

In research published in the journal Nature Communications, the MIT team combined an MRI contrasting agent called nitroxide and a fluorescent molecule called Cy5.5 to produce a nanostructure called a branched bottlebrush polymer. The ratio of the two materials in the nanoparticle is 99 percent nitroxide and 1 percent Cy5.5.

This combination enables both MRIs and fluorescent imaging because of the interesting way these materials interact with each other. The nitroxides are reactive molecules in which a nitrogen atom is bound to an oxygen atom with one unpaired electron. Typically, the nitroxides suppress the Cy5.5’s fluorescence, except when the nitroxides are in the presence of molecule from which they can grab an electron, which, in the case of this study, was a vitamin C molecule. Once the free electrons in the nitroxides bind with the free electrons from another molecule, the MRI signal switches off and the Cy5.5 fluoresces.

In the study, which used mice as subjects, the researchers found that the nanoparticles headed towards the liver, where nanoparticles typically end up. It was there that the nanoparticles came in contact with vitamin C (which is produced by the mouse's liver), the MRI signals were turned off, and the Cy5.5 began to fluoresce. Vitamin C ultimately finds its way to a mouse’s brain, and so the researchers were able to detect fluorescence there. Meanwhile, in areas where the concentration of vitamin C was low, the MRI contrast proved to be strong.

The researchers continue to work on enhancing the signal differences that occur when the nanoparticles encounter a target molecule, such as vitamin C. They have also experimented with adding up to three different drugs to the nanostructure. The aim of having these drugs hitch a ride on the nanostructure is to give diagnosticians the ability to track whether they reach their intended target. A fair amount of research is currently being done in this area, wherein nanoparticles behave as both diagnostic tools and therapeutic devices—a capability that has led to the nanoparticles being dubbed “theranostic” nanoparticles.

“That’s the advantage of our platform—we can mix and match and add almost anything we want,” said Jeremiah Johnson, an assistant professor of chemistry at MIT and senior author of the study, in a press release.

The researchers also believe that this platform should allow detection of oxygen radicals inside a patient’s tumor—a biomarker that can indicate how aggressive the tumor is.

“We think we may be able to reveal information about the tumor environment with these kinds of probes, if we can get them there,” said Johnson. “Someday you might be able to inject this in a patient and obtain real-time biochemical information about disease sites and also healthy tissues, which is not always straightforward.”

The Conversation (0)

This CAD Program Can Design New Organisms

Genetic engineers have a powerful new tool to write and edit DNA code

11 min read
A photo showing machinery in a lab

Foundries such as the Edinburgh Genome Foundry assemble fragments of synthetic DNA and send them to labs for testing in cells.

Edinburgh Genome Foundry, University of Edinburgh

In the next decade, medical science may finally advance cures for some of the most complex diseases that plague humanity. Many diseases are caused by mutations in the human genome, which can either be inherited from our parents (such as in cystic fibrosis), or acquired during life, such as most types of cancer. For some of these conditions, medical researchers have identified the exact mutations that lead to disease; but in many more, they're still seeking answers. And without understanding the cause of a problem, it's pretty tough to find a cure.

We believe that a key enabling technology in this quest is a computer-aided design (CAD) program for genome editing, which our organization is launching this week at the Genome Project-write (GP-write) conference.

With this CAD program, medical researchers will be able to quickly design hundreds of different genomes with any combination of mutations and send the genetic code to a company that manufactures strings of DNA. Those fragments of synthesized DNA can then be sent to a foundry for assembly, and finally to a lab where the designed genomes can be tested in cells. Based on how the cells grow, researchers can use the CAD program to iterate with a new batch of redesigned genomes, sharing data for collaborative efforts. Enabling fast redesign of thousands of variants can only be achieved through automation; at that scale, researchers just might identify the combinations of mutations that are causing genetic diseases. This is the first critical R&D step toward finding cures.

Keep Reading ↓ Show less