Long Island scientists on the trail of health risks in everyday products say pure gold nanoparticles in cosmetics, pharmaceuticals and other medical substances may accelerate aging, increase wrinkling and slow the wound-healing process.
The analysis, centered at Stony Brook University, grows out of a collaboration among diverse scientific enterprises -- human skin research, chemical engineering and materials science. The latter discipline, devoted to studying properties of matter, has zeroed in on nanoparticles as an active field of investigation.
Nanoparticles are infinitesimally -- almost unimaginably -- small flecks of matter, and are being used in a growing array of products.
Stony Brook scientists wanted to find out how they affected human cells.
"Since they have been considered inert and essentially harmless, it was assumed that pure gold nanoparticles would also be safe," said Tatsiana Mironava, a visiting professor of chemical and molecular engineering. "Evidence to the contrary is beginning to emerge."
The series of experiments conducted at Stony Brook appear in the current issue of the journal Nanotoxicology.
Miriam Rafailovich, who holds the title of distinguished professor of materials science, said the research was carried out in lab dishes, a so-called in vitro study of human cells.
"Gold nanoparticles are in cosmetics because they have such interesting colors. You can get yellows and browns, all the way down to blues and purples," said Rafailovich, who is also chief scientist of Stony Brook's Advanced Energy Center.
The tiny flecks, Rafailovich added, are also in pharmaceuticals and MRI contrast agents.
The agents are generally consumed or received intravenously before a scan. The compounds improve MRI images by temporarily altering the activity of atoms in the body's tissues.
When examining the effects of gold nanoparticles on human cells in the laboratory, Rafailovich and her collaborators found that certain fat-derived stromal cells -- a type of adult stem cell -- were not only easily and instantly penetrated, but the flecks accumulated with no pathway for elimination.
Dr. Marcia Simon, director of the university's Living Skin Bank, a facility that develops skin tissue for burn victims, said the particles disrupted multiple cell functions, such as movement, replication and collagen contraction -- processes essential to wound healing.
Most disturbing, the scientists said, was their discovery that the particles interfered with gene regulation and inhibited the ability of fat cells to mature and carry out critical functions. The gold also enhanced wrinkling.
Still, said Simon, who is expected within the coming months to announce the opening of a new artificial skin center at Stony Brook, the findings should be taken with a dose of caution.
As yet, there have been no studies in an animal model, which are now slated to soon occur to help explain the tissue findings.
"We were actually quite surprised to find that gold nanoparticles not only influenced adipose [fat] cells but also the rate at which they could mature," Simon said.
Scientists have long known that human cells have a variety of transport proteins that direct what enters them and what gets sloughed off as harmful debris. Gold nanoparticles, Rafailovich said, appear to stealthily bypass all blockades.
"Nanoparticles seem to fall beneath the radar," she added. "They will penetrate cells immediately whether cells want them or not. They just come in and there is no mechanism for digesting them."
Pharmaceutical giant AstraZeneca recently announced, for example, that a new cancer therapy will rely on the flecks as vehicles to ferry an anti-tumor drug into patients' cells. Gold nanoparticles, according to the drugmaker, will help direct the medication precisely to the tumor, leaving healthy cells unscathed. The company said there are no harmful side effects from gold nanoparticles.