September 12, 2008: 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.
In a forthcoming issue of the Germany-based chemistry journal Angewandte Chemie, scientists at the U. of California/San Diego, UC/Santa Barbara, and MIT report that their nano cargo-ship system integrates therapeutic and diagnostic functions into a single device that avoids rapid removal by the body’s natural immune system.
“The idea involves encapsulating imaging agents and drugs into a protective ‘mother ship’ that evades the natural processes that normally would remove these payloads if they were unprotected,” said Michael Sailor, a professor of chemistry and biochemistry at UCSD who headed the team of chemists, biologists and engineers that turned the fanciful concept into reality.
These “mother ships,” 50nm in diameter, are equipped with an array of molecules on the surface that help target and penetrate tumor cells in the body. Sailor thinks they eventually could be the key to more effectively deliver toxic anti-cancer drugs to tumors in high concentrations without harming other parts of the body.
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 (MRI) scan, while the quantum dots can be seen with a fluorescence scanner which provides higher resolution.
UCSD graduate student Ji-Ho Park holds a vial containing the nanometer-sized cargo ships, composed of a magnetic nanoparticle, a fluorescent quantum dot and an anti-cancer drug molecule that will be left on the site of the tumor. (Source: Luo Gu, UCSD)
“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,” said Sailor, in a statement.
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,” he said. “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.”
A vial of anti-cancer nano ships glows red under a black light. The particles glow red because they contain fluorescent “quantum dot” nanoparticles. (Source: Luo Gu, UCSD)