In vivo imaging of hydrogen peroxide with chemiluminescent nanoparticles

Sep 27 2007

Most people think of hydrogen peroxide as a topical germ killer, but the medicine cabinet staple is gaining steam in the medical community as an early indicator of disease in the body.

Furthering that trend, Georgia Institute of Technology and Emory University researchers have created the first nanoparticle capable of detecting and imaging trace amounts of hydrogen peroxide in animals. The nanoparticles, thought to be completely nontoxic, could someday be used as a simple, all-purpose diagnostic tool to detect the earliest stages of any disease that involves chronic inflammation, including cancer, Alzheimer's disease, heart disease, and arthritis.

Hydrogen peroxide is thought to be overproduced by cells at the early stages of most diseases. Because there were previously no imaging techniques available to capture this process in the body, the details of how the hydrogen peroxide is produced and its role in a developing disease must still be determined. The new nanoparticles, described in a paper published in the journal Nature Materials, may be the key to better understanding the role of hydrogen peroxide in the progression of many diseases and later play an important diagnostic role. This research was led by Niren Murthy, Ph.D., at Georgia Tech and Emory University, and Robert Taylor, M.D., at the Emory University School of Medicine.

"These nanoparticles are incredibly sensitive, so you can detect nanomolar concentrations of hydrogen peroxide. That's important because researchers aren't yet certain what amounts of hydrogen peroxide are present in various diseases," Murthy said.

The ultimate goal, however, is that the nanoparticles could someday be used as a simple, all-purpose diagnostic tool for most diseases. In the future, the nanoparticle would be injected into a certain area of the body. If the nanoparticles encountered hydrogen peroxide, they would emit light. Should a doctor see a significant amount of light activity in the area, the doctor would know that the patient may be presenting early signs of a disease in that area of the body.

The nanoparticle polymer is made of peroxalate esters. A fluorescent dye is then encapsulated into the polymer. When the nanoparticles encounter hydrogen peroxide, the dye becomes excited, emitting photons (or light) that can be detected in a simple, photon-counting scan.

"It's using this nanoparticle made of peroxalate esters that allows you to do this three-component reaction in vivo. If you were to inject a peroxalate ester and a dye, they would go their own ways once in the body. With the nanoparticles, we can sequester both of these reagents within nanometers of each other in vivo," Murthy said.

This work is detailed in the paper, "In vivo imaging of hydrogen peroxide with chemiluminescent nanoparticles." Investigators from the Atlanta Veterans Affairs Medical Center also participated in this study. This paper was published online in advance of print publication. An abstract is available through PubMed. View abstract.