 In the 1966 movie, Fantastic Voyage, scientists find a way to shrink a submarine to microscopic dimensions, then inject it into the bloodstream of a diplomat to remove a blood clot from his brain.
Forty years later, life is imitating art. This time, it’s not submarines, but microscopic “nanoworms” designed by chemists at UC San Diego. The nanoworms behave like tiny cruise missiles, evading the body’s immune defense system, as they home in and destroy tumors.
“Most nanoparticles are recognized by the body's protective mechanisms, which capture and remove them from the bloodstream within a few minutes,” says Michael Sailor, a chemistry and biochemistry professor who headed the team of scientists at UC San Diego, UC Santa Barbara and MIT. “The reason these worms work so well is due to a combination of their shape and to a polymer coating on their surfaces that allows the nanoworms to evade these natural elimination processes.”
The chemists, who recently detailed their discovery in the journal Advanced Materials, constructed their nanoworms from spherical iron oxide nanoparticles. These particles join together, like segments of an earthworm, to produce tiny, gummy worm-like structures about 30 nanometers long—or about 3 million times smaller than an actual earthworm. Their iron-oxide composition allows the nanoworms to show up brightly in diagnostic devices, specifically the MRI machines used to find tumors.
Researchers at UC Santa Barbara coated the nanoworms with a tumor-specific molecule, a peptide called F3 that allowed them to target tumors.
Bioengineers at MIT then verified that the nanoworms homed in on tumor sites by injecting them into the bloodstream of mice with tumors and followed the aggregation of the nanoworms on the sites. Unlike the spherical nanoparticles of similar size that were shuttled out of the blood by the immune system, nanoworms remained in the bloodstream for hours.
Sailor’s research team, which included Ji-Ho Park and Michael Schwartz, is 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.
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