Magnetic microrobots in the body to regenerate knee cartilage

Microrobots that, once grafted into the body, can regenerate the cartilage of the knee, at least in rabbits: this is the result achieved by some researchers from various Chinese institutes and one Korean who published their study in Science Advances.

One of the most common disorders of older people is cartilage degeneration, especially in the hips and knees. The most common treatment to date is to replace the knee or hip joint with artificial devices. This is quite a serious problem considering also that the populations in the world are getting older and older and therefore problems like these, related to cartilage, are more and more widespread.

Previous research, however, had already shown that mesenchymal stem cells, those present in bone marrow and fat, can be transformed into cartilage cells in the laboratory and can also be used to repair damaged cartilage. However, the challenge has been to graft these special cells into the body and keep them in the right position to attach them to the surrounding tissue and trigger cartilage regrowth.

It seems that Chinese and Korean researchers have succeeded in just that: they created tiny hollow spheres with holes made from a polymer called PLGA or poly(lactic-co-glycolic acid). These small spheres were then sprinkled with a mixture of ferumoxytol (iron oxide) and chitosan (a sugar). The same balls were then filled with mesenchymal stem cells previously grown in the laboratory.

Finally, the same balls were inserted into the knees of various rabbits with damaged cartilage. Magnets from outside the body were used to hold them in place. After three weeks the researchers noticed that the cartilage of the rabbits’ knees showed signs of rejuvenation and at the same time the balls were emptying.

Now the researchers want to test animals with knees more similar to those of humans to see if such a technique can be used on people.

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Microrobots as big as insects can fly and move on land and water

Robots the size of insects were built by researchers at the University of Washington. Called RoboFly, they are small winged robots weighing only around 150 pounds that can fly, move on the ground and even touch the surface of the water.

As explained in an article presented on arXiv, taken from Tech Xplore, these small robots have fewer components than other robots of similar size, which of course makes them easier to build. The small robots try to imitate their biological counterpart by performing a sort of multimodal locomotion: aerial flight, earth movement and movement on the water surface.

The RoboFly is an adaptation of the RoboBee, another microrobot that Sawyer Fuller, one of the authors of this project, had already developed near Harvard University. To simplify the construction of such small robots, which are usually made under the microscope because they have to be assembled with extreme precision, the researchers invented a new method: a single sheet of laminate can be bent to form the robot and therefore there are no parts to attach or assemble.

Thanks to its flapping wings, when it flies through the air it can easily steer and change direction, just like insects do. It can also glide over water as well as walk on land, making it a unique microrobot.

Potential uses could see search and rescue missions or missions to look for pollutants or leakage of dangerous fluids into the water.

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