Scientists have developed nanometer-sized 'cargo ships' that can sail throughout the body via the bloodstream without immediate detection from the body's immune radar system and ferry their cargo of anti-cancer drugs and markers into tumors that might otherwise go untreated or undetected. |
"We are now constructing 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."
The researchers loaded their ships with three payloads before injecting them in the mice. Two types of nanoparticles, superparamagnetic iron oxide and fluorescent quantum dots, were placed in the ship's cargo hold, along with the anti-cancer drug doxorubicin. The iron oxide nanoparticles allow the ships to show up in a Magnetic Resonance Imaging, or MRI, scan, while the quantum dots can be seen with another type of imaging tool, a fluorescence scanner.
"The fluorescence image provides higher resolution than MRI," said Sailor. "One can imagine a surgeon identifying the specific location of a tumor in the body before surgery with an MRI scan, then using fluorescence imaging to find and remove all parts of the tumor during the operation."
The team found to its surprise in its experiments that a single mother-ship can carry multiple iron oxide nanoparticles, which increases their brightness in the MRI image.
"The ability of these nanostructures to carry more than one superparamagnetic nanoparticle makes them easier to see by MRI, which should translate to earlier detection of smaller tumors," said Sailor. "The fact that the ships can carry very dissimilar payloads—a magnetic nanoparticle, a fluorescent quantum dot, and a small molecule drug—was a real surprise."
The researchers noted that the construction of so-called "hybrid nanosystems" that contain multiple different types of nanoparticles is being explored by several other research groups. While hybrids have been used for various laboratory applications outside of living systems, said Sailor, there are limited studies done in vivo, or within live organisms, particularly for cancer imaging and therapy.
"That's because of the poor stability and short circulation times within the blood generally observed for these more complicated nanostructures," he added. As a result, the latest study is unique in one important way.
"This study provides the first example of a single nanomaterial used for simultaneous drug delivery and multimode imaging of diseased tissue in a live animal," said Ji-Ho Park, a graduate student in Sailor's laboratory who was part of the team. Geoffrey von Maltzahn, a graduate student working in Bhatia's laboratory, was also involved in the project, which was financed by a grant from the National Cancer Institute of the National Institutes of Health.
The nano mother ships look individually like a chocolate-covered nut cluster, in which a biocompatible lipid forms the chocolate shell and magnetic nanoparticles, quantum dots and the drug doxorubicin are the nuts. They sail through the bloodstream in groups that, under the electron microscope, look like small, broken strands of pearls.
The researchers are now working on developing ways to chemically treat the exteriors of the nano ships with specific chemical "zip codes," that will allow them to be delivered to specific tumors, organs and other sites in the body. ###
Contact: Kim McDonald kimmcdonald@ucsd.edu 858-534-7572 University of California - San Diego
Tags: Nano or Nanotechnology and Nanotech
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