A large group of US researchers have developed tiny robots, known as magnetically aligned nanorods in alginate capsules (MANiACs), that could act as drug delivery vehicles for neural tissue in the future. Their study found that when controlled using a magnetic field, the robots can move against fluid flow, climb slopes and move about neural tissues, such as the spinal cord, and deposit substances at precise locations.    

“Delivering drugs orally or intravenously, for example, to target cancers or neurologic diseases, may affect regions of the body and nervous system that are unrelated to the disease,” explained Lamar Mair at Weinberg Medical Physics, a US medical device company and partner on the study. “Targeted drug delivery may lead to improved efficacy and reduced side-effects due to lower off-target dosing.”

Researchers have previously aimed to achieve targeted dosing using tiny robots to deliver drugs to specific locations. While the technology is in its infancy, researchers have developed various types of micro- or millirobots that could fulfil this goal. However, the major problem lies in controlling their activity as they travel through tissues in the body, and few researchers have put their tumbling robots to the challenge by seeing how they handle moving across real tissues.

To solve this problem, the team used magnetic nanorods encased in a soft spherical shell which allow them to tumble through the body in response to a magnetic field applied externally with the goal of drawing them to a target site for drug delivery. They obtained rat brains and mouse spinal cords to test the robots’ ability to move along the tissues and deposit a dye on their surfaces, as a substitute for a drug.

To test their MANiACs in conditions more similar to the human body, the team placed the robots of scaled slopes as steep at 45 degrees under magnetic stimulation. The robots successfully moved upstream against a fluid flow that was similar to what they would encounter in the nervous system.  The researchers were able to manoeuvre dye-loaded MANiACs around on the surface of rodent neural tissues with a fine degree of control and successfully deposited the dye in specific locations. They also re-dosed several locations to increase the amount of ‘drug’ in that region.

“The ability to go back and re-dose regions which received insufficient dose upon initial treatment is significant,” said Professor David Cappelleri, a researcher involved in the study. “These results are very preliminary and highly experimental, but we think we have demonstrated strong evidence that small, soft, capsule-based microrobots have potential for controlled local delivery in neural diseases.”

The study was published in Frontier in Robotic and AI.