Recent tests show that injectable nanoparticles can quickly neutralize a process that occurs after traumatic injuries, such as a stroke.

When such injuries occur, thousands of damaging reactive oxygen species molecules are overexpressed by the body’s cells. These molecules damage cells and cause mutations.

The nanoparticles, known as poly(ethylene glycol)-functionalized hydrophilic carbon clusters (PEG-HCCs), appear to quickly stem the process of overoxidation by turning the dangerous molecules into less reactive substances.

Researchers hope an injection of PEG-HCCs as soon as possible after an injury, such as traumatic brain injury or stroke, can mitigate further brain damage by restoring normal oxygen levels to the brain’s sensitive circulatory system. Says James Tour, a chemistry professor at Rice University:

“Effectively, they bring the level of reactive oxygen species back to normal almost instantly. This could be a useful tool for emergency responders who need to quickly stabilize an accident or heart attack victim or to treat soldiers in the field of battle.”

Tour led the new study with neurologist Thomas Kent of Baylor College of Medicine and biochemist Ah-Lim Tsai of the University of Texas Health Science Center at Houston Medical School.


PEG-HCCs are about 3 nanometers wide and 30 to 40 nanometers long and contain from 2,000 to 5,000 carbon atoms.

In tests, an individual PEG-HCC nanoparticle can catalyze the conversion of 20,000 to a million reactive oxygen species molecules per second into molecular oxygen, which damaged tissues need, and hydrogen peroxide while quenching reactive intermediates.

Tour and Kent led earlier research that determined an infusion of nontoxic PEG-HCCs may quickly stabilize blood flow in the brain and protect against reactive oxygen species molecules overexpressed by cells during a medical trauma, especially when accompanied by massive blood loss.

Their research targeted traumatic brain injuries, after which cells release an excessive amount of the reactive oxygen species known as a superoxide into the blood.

Thousands of Superoxides

These toxic free radicals are molecules with one unpaired electron that the immune system uses to kill invading microorganisms.

In small concentrations, they contribute to a cell’s normal energy regulation. Generally, they are kept in check by superoxide dismutase, an enzyme that neutralizes superoxides.

But even mild traumas can release enough superoxides to overwhelm the brain’s natural defenses. In turn, superoxides can form such other reactive oxygen species as peroxynitrite that cause further damage.

“The current research shows PEG-HCCs work catalytically, extremely rapidly, and with an enormous capacity to neutralize thousands upon thousands of the deleterious molecules, particularly superoxide and hydroxyl radicals that destroy normal tissue when left unregulated,” Tour says.

“This will be important not only in traumatic brain injury and stroke treatment, but for many acute injuries of any organ or tissue and in medical procedures such as organ transplantation,” he concludes. “Anytime tissue is stressed and thereby oxygen-starved, superoxide can form to further attack the surrounding good tissue.”

Errol L. G. Samuel, et al. Highly efficient conversion of superoxide to oxygen using hydrophilic carbon clusters PNAS February 24, 2015 vol. 112 no. 8 2343-2348

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