Scientists are at work on a new batch of gadolinium-free contrast agents that could be manipulated to target tumors, one day potentially making MRI cancer scans more accurate.

In a press release, researchers with the University of Pennsylvania say they're working on a way to use sugar-coated iron-oxide nanoparticles to pool around tumors, making them visible on MRI scans.

The scientists, Andrew Tsourkas and Samuel H. Crayton, published their work in the current issue of ACS Nano.

Iron-oxide nanoparticles have been used before as MRI contrast agents, although in the United States, many are now commercially unavailable.

The scientists said the substances are often coated with a sugar to allow them to safely pass through the body. In the experiment, though, the coating was tweaked to allow the nanoparticles to target tumors. To do this, the researchers coated them with glycol chitosan, a water-soluble polymer that is sensitive to acid.

This sensitivity to acids could help the particles congregate around malignant tumors: lactic acid often builds up around tumors, giving their neighborhoods a lower pH, meaning the nanoparticles would be active near the tumors and nowhere else in the body.

If successful, the agent could also be used for delivering cancer-fighting drugs, the researchers said.

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