When tiny medical robots are deployed into living tissue to offer a helpful drug or repair damage, they’re met with open hostility from the organism’s own immune system. White blood cells have been rigorously trained to recognize and dispose of invaders. They can’t be convinced of the robots’ good intentions, and proceed to dismantle them before they can do any good.
Researchers who study these bots have instead looked to transform native immune cells into turncoats, and create the molecular equivalent of a sheep in wolf’s clothes.
A group of Chinese researchers from Jinan University’s Institute of Nanophotonics made one type of immune cell, called a neutrophil, do their bidding and avoid destruction in this way. They’ve written a new study published Wednesday in ACS Central Science detailing how laser beams deployed like a pair of “optical tweezers” can be used to control and manipulate neutrophils in the tails of zebrafish—opening the door to leveraging the immune system to help deliver drugs and treat conditions in the body in more specific and unique ways.
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In contrast to traditional medical microbots, their “neutrobots” consist entirely of natural tissue and do not require invasive implantation, “thus avoiding complicated preparation technology and unavoidable tissue damage,” the scientists wrote in the paper.
The laser method, which had not yet been shown to work in a living organism, acts like “a steering wheel for navigation,” the researchers wrote. It can physically push these cells around and direct them to different spaces—or entrap them in a single location, if so desired.
They intentionally chose a wavelength of light that would not be absorbed well into the zebrafish’s surrounding tissue, and they worked with a part of the tiny organism that is naturally translucent.
Once they entrapped the neutrophils under a laser beam, the researchers treated them like miniature robots. But even under the researchers’ mind control, the neutrobots could still act like regular neutrophils, moving around the tail of the zebrafish, entering an injured blood vessel, and switching into an activated state. Using additional laser beams, the researchers found that they were able to control up to 10 neutrobots at a time.
The scientists then took their molecular shepherding a step further by making a neutrobot consume a stand-in for a nanoparticle medicine. The paper describes inducing their captured neutrophil to engulf a nanoparticle “like picking up a passenger,” then release it in a desired zone “like dropping off a passenger.”
Harnessed neutrobots, the researchers wrote, “might provide new insight for the construction of native medical microdevices for drug delivery and precise treatment of inflammatory diseases.”
