Antioxidant-filled nanoparticles injected under the skin may become a future multiple sclerosis (MS) treatment that comes with a perk or a drawback, depending on how a patient sees it. The injection leaves a temporary dark spot on the skin, resembling a tattoo.
The tattoo might be a small issue considering that the particles have a huge advantage. They only inactivate immune T-cells — the main cell type driving MS — leaving other immune cells unaffected, potentially reducing side effects.
The proof-of-concept study, “Preferential uptake of antioxidant carbon nanoparticles by T lymphocytes for immunomodulation,” published in the journal Scientific Reports, was a joint effort between researchers at Baylor College of Medicine and Rice University, both in Texas.
“The majority of current treatments are general, broad-spectrum immunosuppressants,” Redwan Huq, lead author of the study and a graduate student at Baylor, said in a news release. “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. So we get excited when we see something new that could potentially enable selectivity,”
The nanoparticles were created in the lab of James Tour at Rice, one of the two senior authors of the study, and have been explored in cancer and traumatic brain injury. When Christine Beeton, associate professor at Baylor, senior author of the study and an expert in autoimmune diseases, learned about the nanoparticles, she immediately got a hunch that they may be effective against immune cells.
Earlier studies have shown that the particles, which are made from polyethylene glycol and water-soluble carbon clusters, have potent antioxidant properties, removing a type of reactive oxygen species called superoxide. Immune cells use superoxide to kill microbes. Previous studies have shown that the particles are not toxic to experimental animals, at least not in the short run.
Researchers injected the nanoparticles under the skin of rats and were surprised to find that they were taken up only by T-cells, leaving macrophages and other cells produced in the spleen unaffected.
“It was completely unexpected,” said Beeton. Because superoxide is required by T-cells to become activated, the particles prevented T-cell actions without killing them. “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 added.
The experiments showed that the nanoparticles were slowly released into the bloodstream after injection where they entered T-cells. After a few days, the particles were removed from T-cells.
This is a crucial finding because it is important for a drug to stay in the body long enough to be effective, but then eliminated within a reasonable time.
Beeton figured that injecting the nanoparticles just under the skin rather than directly into the blood would keep them in the body longer — which turned out to be just the case. But the approach had a downside; the injection left a dark spot on the skin that resembled a tattoo.
“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,” said Beeton. “But we can work around that. We can inject into an area that’s hidden, or use micropattern needles and shape it.”
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