A temporary tattoo to help control a chronic disease might be possible some day, according to scientists at Baylor College of Medicine who tested antioxidant nanoparticles created at Rice University.
A proof-of-principle study published online in Nature Scientific Reports has shown that nanoparticles modified with polyethylene glycol (PEG) are conveniently choosy as they are taken up by cells in the immune system. That could be a plus for patients with autoimmune diseases, such as multiple sclerosis.
“Placed just under the skin, the carbon-based particles form a dark spot that fades over about one week as they are slowly released into the circulation,” explained lead investigator Dr. Christine Beeton.
T and B lymphocyte cells and macrophages are key components of the immune system. However, T cells are also the key players in many autoimmune diseases. One suspected cause is that T cells lose their ability to distinguish between invaders and healthy tissue and attack both.
In tests at Baylor, nanoparticles were internalized by T cells, which inhibited their function, but were ignored by macrophages. “The ability to selectively inhibit one type of cell over others in the same environment may help doctors gain more control over autoimmune diseases,” Beeton said.
The soluble nanoparticles synthesized at Rice University showed no signs of acute toxicity in rodent studies, according to lead author Dr. Redwan Huq. The nanoparticles combine PEG with hydrophilic carbon clusters (HCCs)––hence their name, PEG-HCCs. The carbon clusters are 35 nanometers long, 3 nanometers wide, and an atom thick, and bulk up to approximately 100 nanometers in globular form with the addition of PEG. They have proven to be efficient scavengers of reactive oxygen species called superoxide molecules, which are expressed by cells that the immune system uses to kill invading microorganisms.
T cells use superoxide in a signaling step to become activated. PEG-HCCs remove this superoxide from the T cells, preventing their activation without killing the cells.
Beeton suggested that delivering carbon nanoparticles just under the skin rather than into the bloodstream would keep them in the system longer, making them more-available for uptake by T cells. And the one drawback––a temporary but visible spot on the skin that looks like a tattoo––could actually be a perk to some patients.
“We saw it made a black mark when we injected it, and at first we thought that’s going to be a real problem if we ever take it into the clinic,” Beeton said. “But we can work around that. We can inject into an area that’s hidden, or use micropattern needles and shape it.
“I can see doing this for a child who wants a tattoo and could never get her parents to go along,” she said. “This will be a good way to convince them.”