Mucus lines and protects the lungs, stomach, intestines, and eyes, and protects cells from pathogens and irritants by trapping them in a sticky membrane. But this protection can also prevent some drug treatments from getting through.
Mucus might not be the first place you’d expect to find tiny robots, but they could solve the problem of delivering certain drugs to their intended locations. The drug molecule could be attached to a tiny nanoparticle that helps it slip through the barrier more easily, or it could be combined with other compounds that help thin the mucus.
So the chemist, a researcher at the Institute of Bioengineering of Catalonia and the Barcelona Institute of Science and Technology, and his colleagues at the American Chemical Society combined these strategies and created nanorobots powered by the mucus-busting compound hydrogen peroxide.
The results, published in the journal ACS Nano on July 17, show that tiny enzyme-powered “mucobots” can move through the sticky defense layer, and potentially deliver drugs more effectively.
To build the nanorobots, the researchers attached catalase enzymes to the porous silica particles. Catalase is an antioxidant enzyme that breaks down hydrogen peroxide into water and oxygen.
The pores in these particles can be filled with drug molecules, helping them slip past mucosal defenses. Initial tests showed that catalase enzymes propelled the robots by using hydrogen peroxide as fuel and converting it into oxygen and water.
The team then built a model of the intestinal mucus layer using human intestinal cells grown in the lab, and the robots passed through the mucus layer in the model in 15 minutes without significantly damaging the cells underneath.
Given that mucus is typically cleared and renewed every 10 minutes to 4.5 hours, this rapid time frame could prevent robots from being trapped or removed by the mucus layer.
Additional tests in the colons of mice supported this finding, showing that the nanorobots did not cause cell or tissue damage while crossing the viscous layer. The researchers believe, according to the EurekAlert website, that their mucosal robots are promising candidates for drug delivery systems, especially to those places where the mucus barrier is obstructed.