Tiny tentacled particles could camouflage implants from immune rejection

Our immune system is a powerful ally to keep us safe, but there are times when it gets a little carried away and attacks things that are trying to help us. Now, researchers have developed particles called dendrimers that are covered in tiny tentacles, arranged in patterns too small for the immune system to detect. These could be handy for delivering drugs or camouflaging implants to prevent rejection.

Dendrimers are particles made up of tree-like branches extending out in a sphere from a central core. Scientists have been experimenting with them for decades for their ability to carry drugs, kill bacteria, and even make glues that can be activated by electric charges.

But for the new study, led by Newcastle University, researchers discovered an intriguing new feature of dendrimers that could greatly extend their usefulness. The larger a dendrimer grows, the more tentacles it sprouts, and the less space there is between them. And at a certain point that seems to make them undetectable to the immune system.

Sensors called complement pattern-recognition (CPR) molecules help immune cells recognize foreign pathogens like bacteria and viruses, thanks to unique patterns on their surface. These CPR molecules can react to patterns that repeat within a range of about 2 to 15 nanometers – but any smaller than that, and the immune cells can’t pick them out of a lineup. Sure enough, the team found that when they made dendrimers with tentacles spaced less than 1 nm apart, CPR molecules failed to detect them.

“This discovery shows that we can develop certain dendrimers as very tiny carriers to smuggle drugs into the body without triggering our immune system,” says Professor Moein Moghimi, corresponding author of the study. “Activation of the complement system as the defence mechanisms of our immune system can sometimes result in inflammation and may also induce anaphylactic reactions.”

The team says that this kind of nanoscale texturing could potentially be used to camouflage cardiovascular stents and other medical implants, to protect them from rejection by the body. But covert drug delivery could be the most immediately useful application.

“Dendrimers offer us the ability to deliver drugs to diseased sites where inflammation is a major problem such as in conditions like atherosclerosis, cancer, macular degeneration and rheumatoid arthritis,” says Dr. Panagiotis Trohopoulos, co-author of the study. “This could allow medical teams to treat these conditions without triggering the patient’s own immune system.”

The team also suggests that some pathogens may already have figured out this kind of camouflage – certain bacteria and viruses may be using sub-nanometer surface patterns to evade detection by the immune system. Further research will look into this possibility, as well as how we might use dendrimers for drug delivery, device coatings and other applications.

The research was published in the journal Nature Communications.

Source: Newcastle University

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