Researchers have developed new nanoparticles that can be used for magnetic resonance imaging (MRI). This application could help medics to monitor a tumor’s environment and to assess if drugs have successfully reached their targets. In a new study, medical technologists based at MIT have shown how nanoparticles, carrying special sensors for fluorescence and MRI, can be used to follow the progression of vitamin C in mice.
The research findings indicated that where there is a high concentration of vitamin C, the particles show a strong fluorescent signal but little MRI contrast. Conversely, where there was not much vitamin C, a stronger MRI signal was visible and the fluorescence was very weak. The nanoparticles circulated for several hours in a mouse’s bloodstream. This was sufficient time to track the progress of the vitamin C and to obtain images.
For the next stage of the study, the researchers plan to use the nanoparticles to detect reactive oxygen species that tend to correlate with disease. This will be useful in helping to understand how a disease progresses.
Nanoparticles are particles between 1 and 100 nanometers in size (a nanometer is equal to one billionth of a metre.) Nanoparticle characterization is necessary to establish understanding and control of nanoparticle synthesis and applications, this is normally achieved by electron microscopy.
The nanoparticles form the new study were constructed from polymer chains. The chains carried either an organic MRI contrast agent, called a nitroxide, or a fluorescent molecule termed Cy5.5. The two types of particles are used together, at different ratios. This produces a single nanoparticle system.
Nitroxides are reactive molecules that contain a nitrogen atom bound to an oxygen atom with an unpaired electron. When the nitroxides encounter a molecule such as vitamin C they become inactive and Cy5.5 fluoresces.
The findings have been published in the journal Nature Communications. The paper is titled “Redox-responsive branched-bottlebrush polymers for in vivo MRI and fluorescence imaging.”
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