A team of scientists at the University of California, San Diego has found a way to encapsulate micromotors into pills. The pill’s coating protects the devices as they traverse the digestive system prior to releasing their drug cargo.
Karshalev et al created a micromotor pill and demonstrated its attractive use as a platform for oral delivery of active micromotors: (A) left: schematic of in vivo administration of a micromotor pill for actuation in the stomach; right: schematic of the micromotor pill composition consisting of a lactose/maltose pill matrix and the encapsulated a magnesium/titanium dioxide/polylactic-co-glycolic acid (Mg/TiO2/PLGA) micromotors; a zoom-in view illustrates the micromotor structure consisting of a Mg microsphere core with a TiO2 shell layer and a cargo-loaded PLGA film coating; (B) schematic of micromotor pill dissolution in gastric fluid and subsequent micromotor release; (C) left: image showing different sizes of disk-shaped micromotor pills; center: microscope image showing the dissolution of a micromotor pill in gastric fluid simulant; right: propulsion of the released Mg-based micromotors in gastric fluid simulant. Image credit: Karshalev et al, doi: 10.1021/acsnano.8b03760.
About the width of a human hair, micromotors are self-propelled microscopic robots designed to perform a host of biomedical tasks.
In previous research, University of California, San Diego scientists Joseph Wang and Liangfang Zhang and co-authors used micromotors coated with an antibiotic to treat ulcers in lab mice.
They found that this approach produced better results than just taking the drugs by themselves.
However, they noted that body fluids, such as gastric acid and intestinal fluids, can compromise the effectiveness of micromotors and trigger early release of their payloads.
In addition, when taken orally in fluid, some of the micromotors can get trapped in the esophagus.
To overcome these issues, the researchers sought to develop a way to protect and carry these devices into the stomach without compromising their mobility or effectiveness.
They created a pill composed of a pair of sugars (lactose and maltose) that encapsulated tens of thousands of micromotors made of a magnesium/titanium dioxide core loaded with a fluorescent dye cargo.
These sugars were chosen because they are easy to mold into tablet, can disintegrate when needed and are nontoxic.
“When given to mice, these pills improved the release and retention of the micromotors in the stomach compared to those encapsulated in silica-based tablets or in a liquid solution,” the study authors said.
“Encapsulating micromotors in traditional pill form improves their ability to deliver medicines to specific targets without diminishing their mobility or performance.”
The findings appear in the journal ACS Nano.
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Emil Karshalev et al. 2018. Micromotor Pills as a Dynamic Oral Delivery Platform. ACS Nano 12 (8): 8397-8405; doi: 10.1021/acsnano.8b03760
