“Army” of microrobots to destroy bacteria on teeth

Microrobots for bacterial tooth cleaning have been developed by researchers at the School of Dental Medicine and the School of Engineering and Applied Science of the University of Pennsylvania (Penn).

Visiting the dentist, as it is known, involves lengthy and often painful scraping procedures with mechanical tools to remove the plaque from the teeth. Penn’s engineers, dentists and biologists are using a tiny robotic cleaning crew: Using two types of robotic systems -one to work on surfaces and the other in limited spaces- researchers have shown that robots with catalytic activity can be effectively destroy bio-membranes (or biofilm), sticky amalgams of bacteria installed in protective structures. Such biofilm removal robotic systems could be valuable in a wide range of possible applications; from cleaning water and catheter tubes to tooth cleaning, treating intra-dental infections and implant infections.

The research, published in Science Robotics, led by Hun (Michelle) Kou and Edward Stinger.

“We take advantage of the expertise of microbiologists and clinical scientists as well as engineers to design the best possible microbial extermination system. This is important in other areas of biomedicine, which are faced with drug-resistant biofilm as we approach the post-antibiotic era”,

says Kou.

“Treating biofilms that occur in teeth requires a lot of manual work, both from the consumer’s point of view and from the professional point of view. We hope to improve treatment options as well as reduce the difficulty of caring,

says Stinger.

Biomembranes appear on biological surfaces, such as teeth and joints, or on objects such as water pipes, implants, or catheters. When formed, removal is very difficult as the sticky grid that holds the bacteria provides protection from antimicrobial substances.

In their previous work, Kou and colleagues had made progress on the destruction of grids with a number of pioneering methods. One strategy was the use of iron oxide nanoparticles, to catalytic activation of hydrogen peroxide to release bacteria-killing substances and destroying biofilm in a targeted manner. At the same time, Penn Engineering teams under Stiger, as well as Withey Kumar and Kathleen Stibe, were working on a robotic platform that used very similar nanoparticles as building blocks for micro-robots. Engineers control the movement of these robots through a magnetic field.

Together, researchers from these different disciplines designed and tested two kinds of robotic systems, called CAR (catalytic antimicrobial robots), capable of degrading and destroying biofilm. The first is to maintain iron oxide nanoparticles in a solution, then directed through magnets to perform their work: Removing biofilm from a surface in a way that refers to a “plow”. The second platform includes the incorporation of nanoparticles into gel structures in three-dimensional shapes, used for the targeted biofilm disposal in enclosed spaces.

Both types of CAR proved to be effective in destroying bacteria and their grids: First tests were done on flat surfaces or closed glass tubes, and then tests were done on inaccessible parts of human teeth. As it turned out, CARs were able to degrade and destroy bacterial biofilms not only from the tooth surfaces but also from their most inaccessible parts.

“Existing biofilm therapies are ineffective because they can not at the same time degrade the protective grid by killing embedded bacteria and remove the products of this process. These robots can do all three simultaneously, leaving no trace of biofilm“,

notes Kou.