UC San Diego researchers target tumors with tiny 'nanoworms'

“The iron oxide used in the nanoworms has a property of superparamagnetism, which makes them show up very brightly in MRI,” said Sailor. “The magnetism of the individual iron oxide segments, typically eight per nanoworm, combine to provide a much larger signal than can be observed if the segments are separated. This translates to a better ability to see smaller tumors, hopefully enabling physicians to make their diagnosis of cancer at earlier stages of development.”

In addition to the polymer coating, which is derived from the biopolymer dextran, the scientists coated their nanoworms with a tumor-specific targeting molecule, a peptide called F3, developed in the laboratory of Erkki Ruoslahti, a cell biologist and professor at the Burnham Institute for Medical Research at UC Santa Barbara. This peptide allows the nanoworms to target and home in on tumors.

“Because of its elongated shape, the nanoworm can carry many F3 molecules that can simultaneously bind to the tumor surface,” said Sailor. “And this cooperative effect significantly improves the ability of the nanoworm to attach to a tumor.”

The scientists were able to verify in their experiments that their nanoworms homed in on tumor sites by injecting them into the bloodstream of mice with tumors and following the aggregation of the nanoworms on the tumors. They found that the nanoworms, unlike the spherical nanoparticles of similar size that were shuttled out of the blood by the immune system, remained in the bloodstream for hours.

“This is an important property because the longer these nanoworms can stay in the bloodstream, the more chances they have to hit their targets, the tumors,” said Ji-Ho Park, a UC San Diego graduate student in materials science and engineering working in Sailor’s laboratory.

Park was the motivating force behind the discovery when he found by accident that the gummy worm aggregates of nanoparticles stayed for hours in the bloodstream despite their relatively large size.

While it’s not clear yet to the researchers why, Park notes that “the nanoworm’s flexibly moving, one dimensional structure may be one the reasons for its long life in the bloodstream.”

The researchers are now working on developing ways to attach drugs to the nanoworms and chemically treating their exteriors with specific chemical “zip codes,” that will allow them to be delivered to specific tumors, organs and other sites in the body.

“We are now using nanoworms to construct the next generation of smart tumor-targeting nanodevices,” said Ruoslahti. We hope that these devices will improve the diagnostic imaging of cancer and allow pinpoint targeting of treatments into cancerous tumors.”

Other researchers involved in the development were Michael Schwartz of UC San Diego, Geoffrey von Maltzahn of MIT, and Lianglin Zhang of UC Santa Barbara. The project was funded by grants from the National Cancer Institute of the National Institutes of Health.