Solid gold nanoparticles have long been used to treat rheumatoid arthritis and more recently have shown promise in treating various types of cancer.
Now, thanks to work by Shuming Nie, Ph.D., and his colleagues at the Emory-Georgia Tech Nanotechnology Center for Personalized and Predictive Oncology, these same nanoparticles could serve as a powerful tumor-homing beacon for detecting microscopic tumors or even individual malignant cells. The researchers report their findings in the journal Nature Biotechnology.
Starting with colloidal gold—a commercially available suspension of gold nanoparticles—the investigators attached one of several positively charged organic dye molecules to the particles’ surfaces. The chosen dye molecules absorb and emit light in the near-infrared region of the spectrum, a portion of the spectrum that passes unabsorbed through biological tissues. The researchers then added a nanometer-thick layer of polyethylene glycol (PEG) to render the construct biocompatible. To their surprise, this coating also made the resulting optical probe incredibly stable under even harsh chemical conditions. More importantly, the optical properties of both the gold nanoparticles and the dye molecules remained constant even after application of the coating. These particles were also nontoxic to cells over periods as long as 6 days.