“Bubble-Based Microrobots With Rapid Circular Motions for Epithelial Pinning and Drug Delivery”, 2023-04-14 ():
[press release; video] Remotely powered microrobots are proposed as next-generation vehicles for drug delivery. However, most microrobots swim with linear trajectories and lack the capacity to robustly adhere to soft tissues. This limits their ability to navigate complex biological environments and sustainably release drugs at target sites.
In this work, bubble-based microrobots with complex geometries are shown to efficiently swim with non-linear trajectories in a mouse bladder, robustly pin to the epithelium, and slowly release therapeutic drugs. The asymmetric fins on the exterior bodies of the microrobots induce a rapid rotational component to their swimming motions of up to ≈150 body lengths per second. Due to their fast speeds and sharp fins, the microrobots can mechanically pin themselves to the bladder epithelium and endure shear stresses commensurate with urination.
Dexamethasone, a small molecule drug used for inflammatory diseases, is encapsulated within the polymeric bodies of the microrobots. The sustained release of the drug is shown to temper inflammation in a manner that surpasses the performance of free drug controls.
This system provides a potential strategy to use microrobots to efficiently navigate large volumes, pin at soft tissue boundaries, and release drugs over several days for a range of diseases.
[The group’s microrobots are really small. Each one measures only 20 micrometers wide, several times smaller than the width of a human hair. They’re also really fast, capable of traveling at speeds of about 3 millimeters per second, or roughly 9,000× their own length per minute. That’s many times faster than a cheetah in relative terms. They have a lot of potential, too. In the new study, the group deployed fleets of these machines to transport doses of dexamethasone, a common steroid medication, to the bladders of lab mice. The results suggest that microrobots may be a useful tool for treating bladder diseases and other illnesses in people…The team makes its microrobots out of materials called biocompatible polymers using a technology similar to 3D printing. The machines look a bit like small rockets and come complete with 3 tiny fins. They also include a little something extra: Each of the robots carries a small bubble of trapped air, similar to what happens when you dunk a glass upside-down in water. If you expose the machines to an acoustic field, like the kind used in ultrasound, the bubbles will begin to vibrate wildly, pushing water away and shooting the robots forward…In laboratory experiments, the researchers fabricated schools of microrobots encapsulating high concentrations of dexamethasone. They then introduced thousands of those bots into the bladders of lab mice. The result was a real-life Fantastic Voyage: The microrobots dispersed through the organs before sticking onto the bladder walls, which would likely make them difficult to pee out…Such a steady flow of medicine could allow patients to receive more drugs over a longer span of time, Lee said, improving outcomes for patients. He added that the team has a lot of work to do before microrobots can travel through real human bodies. For a start, the group wants to make the machines fully biodegradable so that they would eventually dissolve in the body.]