Medical microrobots that can travel inside your body are (still) on their way

The human body is a complex system with barriers that doctors struggle to break through, making it difficult to diagnose and treat illnesses. However, tiny robots could potentially break up clots, deliver drugs to inaccessible tumors, and guide embryos towards implantation. Brad Nelson, a robotics expert at ETH Zürich, believes these machines could be a game changer in medicine, allowing for stronger doses and potentially rethinking disease treatment.

What makes Nelson optimistic that these technologies are on their way? Some such robots have made their way off the lab bench and into large animals, including pigs. There are at least four startups working on medical microrobots that could travel “untethered” inside the body. One of these, Bionaut, raised $43 million earlier this year to take its therapy into phase 1 trials. It will use the money to develop devices about the size of a pencil tip that are designed to deliver drugs to the site of glioma brain tumors and pierce cysts that block the flow of spinal fluid in the brain, a symptom of a rare childhood disorder called Dandy-Walker syndrome.

“Microrobot” is a catch-all term covering robots that range in size from one micron (about 100th of the width of a human hair) up to a few millimeters in scale. If the robot is really tiny, smaller than a micron, it’s a nanorobot. And while it may be enticing to say “microbot” because it sounds really cool, that’s “more of a Hollywood kind of term,” Nelson says.

Microrobots can be composed of synthetic materials, biological materials (these are called biological robots or biobots), or both (biohybrid robots).  Many of them, including the ones that Nelson is developing, move thanks to magnets.

Researchers from Tufts and Harvard have created biobots from tracheal cells, allowing them to move in various ways. The biobots can travel in straight lines, turn circles, or wiggle depending on their shape and cilia coverage. When a metal rod was scraped across living neurons, the biobots swarmed the area, triggering new neuron growth.

Microrobots have the potential to be used in various applications, including treating vascular diseases, preventing brain bursting, and delivering drugs to specific locations. Researchers at the University of Pennsylvania have developed bots that could replace toothbrushes, while others are working on bots that mimic or are made from sperm. IRONSperm, cow sperm covered in iron nanoparticles, is being developed for targeted drug delivery. Germany's team is working on microrobots that help with fertilization by delivering weakly swimming sperm to the egg and releasing drugs to break down the egg's hard coating. Microrobots could also be used in IVF, allowing embryos to develop under natural conditions, improving implantation rates. However, there are technical hurdles to overcome, as these tiny systems are relatively viscous, making it difficult for the robots to move in the opposite direction.

Other hurdles are regulatory. Microrobots qualify as medical devices, but they  may also be delivering a drug. “You’ve got what’s called the drug-device combination,” Nelson says. “While the drug might be well known, its concentration is going to be hopefully significantly different than normal.” That might mean regulators will want to see additional studies. 

Webster-Wood has been in the field for years, and she is excited that microrobots are finally getting attention. “Even in the last 10 years, it’s just grown so much,” she says. “I think there’s a lot more potential for actually translating.”

This week the FDA is expected to approve Casgevy, the world’s first commercial gene-editing treatment, which treats sickle-cell disease. (The treatment was approved in the UK last month.) Antonio Regalado dug deep into the science behind the treatment for this story, which explains why sickle-cell was an ideal target for CRISPR’s big therapeutic debut. 

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We’ve been thinking about microrobots and medical robots for years. Way back in 2011, Kristina Grifantini covered what was then one of the central puzzles: how to control them.

Earlier this year, Antonio Regalado reported on the first babies conceived with robots and the startups working to automate IVF. These weren’t microrobots, and the goal was mainly to achieve scale. “The main goal of automating IVF, say entrepreneurs, is simple: it’s to make a lot more babies.”

Victoria Webster-Wood, who makes biohybrid robots, and Renee Zhao, who makes millimeter-scale medical robots both made this year’s Tech Review 35 Innovators Under 35 list. 

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