Delivering drugs to internal organs and tissues is usually achieved through ingested medications, but these are often diluted and intercepted before enough can reach the intended destination. Targeted delivery is preferred but usually very difficult to accomplish, particularly when there’s a lot of fluids and movement. This is the case with the colon, an organ that in many patients would benefit immensely if doctors had a way to place drugs on its interior tissues.
Now, engineers at Purdue University have come up with tiny robots, controlled by an external magnetic field, that can tumble through the colon to deliver drugs precisely where needed. They may even serve as a minimally invasive and more comfortable way to take biopsies within the colon.
The individual robots are only a few widths of human hair in size and they move by simply tumbling over themselves. A rotating magnetic field provides the energy for them to move and is also used to direct their travel. Because they tumble, these devices can pass over relatively large objects, such as those found on the irregular surface of the colon’s interior.
The robots are so small that the Purdue team was able to squeeze them through the anuses and into the colons of live mice. Using an ultrasound probe they were able to see the robots as they moved through the colons and found that the devices responded well to the guidance of the magnetic field. The same was tried in excised pig colons with similar results.
“When we apply a rotating external magnetic field to these robots, they rotate just like a car tire would to go over rough terrain,” said David Cappelleri, a Purdue associate professor of mechanical engineering and one of the study leads, in a press release. “The magnetic field also safely penetrates different types of mediums, which is important for using these robots in the human body.”
Finally, these researchers loaded their robots with microscopic drug vials that were filled a fluorescent liquid. The robots were able to deliver their vials to the intended destinations and remained there to let the vials slowly release the fluorescent substance, which was easily detected using a light source.
“We were able to get a nice, controlled release of the drug payload. This means that we could potentially steer the microrobot to a location in the body, leave it there, and then allow the drug to slowly come out. And because the microrobot has a polymer coating, the drug wouldn’t fall off before reaching a target location,” said Luis Solorio, another researcher that developed the robots.
Making these robots is reportedly pretty cheap, and they’re non-toxic and biocompatible for the intended applications. They can also be manufactured in very large quantities, which they will have to be if they are to become clinically useful.
“From a diagnostic perspective, these microrobots might prevent the need for minimally invasive colonoscopies by helping to collect tissue. Or they could deliver payloads without having to do the prep work that’s needed for traditional colonoscopies,” added Craig J. Goerge, another of the researchers.
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