Nanobots propel themselves in the eyes

Researchers at the Max Planck Institute for Intelligent Systems Micro, Nano and Molecular Systems Lab and an international team of scientists have developed helical nanorobots that, for the first time, can piercing dense tissue is shed in one eye. They applied a nonstick coating to the nanoparticles, whose width is only 500 nm – small enough to pass through the narrow molecular matrix of the gelatinous substance in the vitreous. Drills are 200 times smaller than the diameter of a human hair, even smaller than the width of a bacterium. Their shape and slippery coating allows the nanoparticles to move relatively easily through an eye, without damaging the sensitive biological tissue that surrounds them. This is the first time that scientists have been able to direct nanobots through dense tissue, as has been demonstrated until now only in model systems or biological fluids. The researchers' vision is to one day load nanoproters with drugs or other therapeutic agents and direct them to a targeted area, where they can deliver the drug where it is needed.

Targeted delivery of drugs within dense biological tissues is very difficult, especially at these small scales: it is first the viscous consistency of the inside of the eyeball, the narrow molecular matrix to which a nanoparticles must sneak. It acts as a barrier and prevents the penetration of larger structures. Secondly, even if size requirements are met, the chemical properties of the biopolymeric network in the eye could still cause the nanoproject to get stuck in this mesh of molecules. Imagine a small corkscrew crossing a strip of double-sided tape. And thirdly, there is the challenge of precise actuation. Scientists overcame the latter problem by adding a magnetic material, such as iron, during the construction of the nano-propellers, which allowed them to steer the drills with magnetic fields up to the desired destination. Other hurdles that the researchers have overcome are the following: each nanopropellant does not have a size greater than 500 nm and a two-layer non-stick coating. The first layer consists of molecules bound to the surface, while the second layer is a liquid fluorocarbon coating. This significantly decreases the adhesive force between the nanobots and the surrounding tissue.

"For the coating, we turn to nature to inspire ourselves," says lead author Zhiguang Wu. He was a Humboldt researcher at MPI-IS and is now a postdoctoral fellow at the California Institute of Technology. . "In the second step, we applied a layer of liquid found on the carnivorous plant, which has a slippery surface on the peristome to catch the insects, like the Teflon coating of a frying pan. Slippery is crucial for efficient propulsion of our robots inside the eye because it minimizes adhesion between the network of biological proteins in the vitreous and surface of our nanobots. "

"The principle of propulsion of nanobots, their small size, as well as the slippery coating, will be useful not only for the eyes, but also for the penetration of various tissues into the human body," said Tian Qiu. one of the corresponding authors of the article and a group leader of the micro, nano and molecular systems laboratory of MPI-IS.

Qiu and Wu are both part of an international research team that has been working on the publication titled "A swarm of slippery micropropellants enters the vitreous body of the eye". The University of Stuttgart, the Max Planck Institute for Medical Research in Heidelberg, the Harbin Institute of Technology in China, the University of Aarhus in Denmark and the Ophthalmological Hospital of the University of Tübingen also contributed to pioneering work. It was at the ophthalmic hospital, where researchers tested their nanoparticles in a dissected pork eye and observed the movement of the propellers using optical coherence tomography, a clinically approved imaging technique. widely used in the diagnosis of vision. diseases.

Through the eye to the retina

With a small needle, the researchers injected tens of thousands of helical robots the size of a bacterium in the vitreous humor of the eye. With the help of a surrounding magnetic field that rotates the nanoprojectors, these then swim to the retina, where the swarm arises. Sliding nanorobots enter an eye. The goal of the researchers was to be able to precisely control the swarm in real time. But that does not stop there: the team is already working one day on the use of its nano-vehicles for targeted delivery applications. "It's our vision," said Tian Qiu. "We want to be able to use our nanoprojectors as tools in the minimally invasive treatment of all kinds of diseases, where the problem area is hard to reach and surrounded by dense tissue – we will not be able to charge them with drugs."

This is not the first nanorobot developed by researchers. For several years, they have created different types of nanobots using a sophisticated 3D manufacturing process developed by the research group on micro, nano and molecular systems led by Professor Peer Fischer. Billions of nanobots can be made in just a few hours by spraying silicon dioxide and other materials, including iron, on a slice of high vacuum silicon as it turns.

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More information:
Zhiguang Wu et al. A swarm of slippery micropropellants penetrates into the vitreous body of the eye, Progress of science (2018). DOI: 10.1126 / sciadv.aat4388