First use of Metal Nanoparticles IDs Liver Cancer on X-ray

PROVIDENCE – July 8, 2011 – Using metal nanoparticles for the first time as an imaging agent researchers have developed a new technique to detect heptocellular carcinoma at a much earlier, treatable stage than is currently available, a new study suggests.

A new diagnostic technique can spot tumor-like masses as small as 5 millimeters in the liver. Gold nanoparticles with a polyelectrolyte coating can make smaller tumors more visiblethrough X-ray scatter imaging, enabling earlier diagnosis. (credit: Rose-Petruck Lab/Brown University)

Heptocellular carcinoma is the most common cancer of the liver striking more than half a million people worldwide each year. It is especially prevalent in sub-Saharan Africa and Southeast Asia. Because it is usually diagnosed only when tumors have grown to about 5 centimeters in size, most of those afflicted die within six months.  (Link to published site)

“What we’re doing is not a screening method,” said Rose-Petruck, professor of chemistry at Brown University in a prepared statement. “But in a routine exam, with people who have risk factors, such as certain types of hepatitis, we can use this technique to see a tumor that is just a few millimeters in diameter, which, in terms of size, is a factor of 10 smaller.”

The team took gold nanoparticles of 10 and 50 nanometers in diameter and ringed them with a pair of 1-nanometer polyelectrolyte coatings. The coating gave the nanoparticles a charge, which increased the chances the cancerous cells would take them up and engulf them. Once engulfed, the team used x-ray scatter imaging to detect the gold nanoparticles within the malignant cells. In lab tests, the nontoxic gold nanoparticles made up just 0.0006 percent of the cell’s volume, yet the nanoparticles had enough critical mass to be detected by the X-ray scatter imaging device.

It should be noted that the phase-contrast x-ray imaging technique used is fundamentally different from conventional x-ray radiography. The mechanism of image formation does not rely on differential absorption by tissues. Instead, x-ray beams undergo differential phase shifts in passing through an organ and subsequently interfere constructively or destructively at the x-ray camera or film. The result is tissues are distinguished by their different indices of refraction rather than their absorptive properties. This imaging method is more than a thousand times more sensitive to density variations of tissues than conventional absorption methods.

Rose-Petruck says the study demonstrated the ability to distinguish tumor cells even with miniscule numbers of nanoparticles taken up by cancer cells.

In collaboration with Dr. Jack Wands, director of the Liver Research Center at Rhode Island Hospital, Providence, RI, Rose-Petruck’s team are now planning an mouse model experiment that combines the nanoparticles with a monoclonal antibody to more specifically deliver the nanoparticles to tumors.

“We have developed a monoclonal antibody that targets a cell surface protein highly expressed onliver cancer cells,” Wands said. “We plan to couple the antibody to the gold nanoparticles in an attempt to detect the growth of early tumors in the liver by x-ray imaging.”

By Michael O’Leary, contributing writer, Health Imaging Hub