Could Temporary Tattoos Treat Chronic Diseases?

Temporary tattoos may not just be for children.

A new proof-of-principle study published by Scientific Reports found that it may eventually be possible for a temporary “tattoo” to help control chronic diseases. The study showed that nanoparticles modified with polyethylene glycol are conveniently choosy when taken up by cells in the immune system, which could be particularly helpful for patients with autoimmune diseases.

“Placed just under the skin, the carbon-based particles form a dark spot that fades over about 1 week as they are slowly released into the circulation,” said lead researcher Christine Beeton.

Although T and B lymphocyte cells, as well as macrophages, are key components of the immune system, the T cells become key players in patients with autoimmune diseases, such as multiple sclerosis. For the study, the nanoparticles were internalized by T cells, inhibiting their function; however, they were ignored by macrophages.

“The ability to selectively inhibit 1 type of cell over others in the same environment may help doctors gain more control over autoimmune diseases,” Beeton said.

Today, a majority of treatments are general, broad-spectrum immunosuppressants, according to the study.

“They’re going to affect all of these cells, but patients are exposed to side effects [ranging] from infections to increased chances of developing cancer,” said lead study author Redwan Huq. “So we get excited when we see something new that could potentially enable selectivity.”

Huq added that since macrophages and other splenic immune cells remain unaffected, a majority of a patient’s existing immune system stays intact. In prior studies using rodents, researchers discovered that the soluble nanoparticles showed no signs of acute toxicity.

During the study, polyethylene glycol was combined with hydrophilic carbon clusters (PEG-HCCs). The carbon clusters have been shown to be efficient scavengers of superoxide molecules. Before T cells become activated, they use superoxide in a signaling step.

The PEG-HCCs remove the superoxide from the T cells, which prevents their activation without killing the cells. Beeton first became aware of PEG-HCCs while listening to a presentation by study co-author Takeo Inoue.

“As she talked, I was thinking, ‘that has to work in models of multiple sclerosis,’” Beeton said. “I didn’t have a good scientific rationale, but I asked for a small sample of PEG-HCCs to see if they affected immune cells. We found they affected the T lymphocytes and not the other splenic immune cells, like the macrophages. It was completely unexpected.”

In the current study, researchers tested this on animal models. They found that small amounts of PEG-HCCs injected under the skin are slowly taken up by T lymphocytes, where they collect and inhibit the cell’s function.

Furthermore, researchers found that the nanoparticles did not stay in the T cells, but instead dispersed within days after uptake by the cells.

“That’s an issue because you want a drug that’s in the system long enough to be effective, but not so long that, if you have a problem, you can’t remove it,” Beeton said. “PEG-HCCs can be administered for slow release and don’t stay in the system long. This gives us much better control over the circulating half-life.”

One idea by researchers for keeping the nanoparticles in the system longer would be to deliver carbon nanoparticles just under the skin rather than into the blood stream, making them more available for uptake by T cells. The only drawback however, is that a temporary visible spot on the skin will appear that looks like a tattoo.

“We saw it made a black mark when we injected it, and at first we though 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. This will be a good way to convince them.”