Interview: “Current antimicrobial techniques are largely ineffective ”
Robots and their influence on society is not something new. For years, we have been sharing our social and, more recently, private circles with them. In dentistry, the advancement of robotics is steadily progressing, and in a recent interview with Dental Tribune International, Prof. Hyun (Michel) Koo, from the School of Dental Medicine at the University of Pennsylvania, spoke about his work in developing an army of microrobots to combat plaque.
Why did you want to develop something like microrobots to combat plaque, and how did you come up with the idea?
Current antimicrobial techniques are largely ineffective for two reasons. The first is that they do not address the protective mechanisms of biofilms associated with drug resistance and mechanical clearance. The second is the fact that biofilms can rapidly re-establish themselves on a surface if not eradicated and retake hold, causing reinfection. Thus, treating and removing biofilms poses a major technical and societal challenge, especially as we approach a post-antibiotic era and are faced with the alarming rise of drug-resistant microbes.
In our previous work, we discovered that iron oxide-containing nanoparticles (NPs) work catalytically, activating hydrogen peroxide to release free radicals that can kill bacteria and destroy biofilms in a targeted fashion. Serendipitously, we found that groups at Penn Engineering led by Dr. Edward Steager, Prof. Vijay Kumar and Prof. Kathleen Stebe were working with a robotic platform that used very similar iron oxide NPs as building blocks for microrobots. The engineers could control the movement of these robots using a magnetic field, allowing a tether-free way to steer them very precisely. Our groups connected immediately and the idea of combining the anti-biofilm properties of iron oxide NPs with robotics principles for control was born.
For us, this was critical because, although the iron oxide NPs could kill and degrade biofilms, we had no idea whatsoever about how to remove the biofilm debris that was left over. The Penn Engineering team brought up an amazing and readily applicable solution by integrating a robotics approach to solve this limitation.
Together, the cross-school team designed, optimized and tested these catalytic antimicrobial robots, or CARs, that are capable of killing, degrading and removing biofilms efficiently and with high precision.
How exactly does the system work?
The robots were designed to tackle all biofilm resistance mechanisms by simultaneously degrading the protective matrix, killing the embedded bacteria and physically removing the biodegraded products. These robots can do all three activities at once very effectively, leaving no trace of biofilm whatsoever
We use catalytic and magnetic NPs that have a dual function: First they produce chemicals that kill bacteria and then they degrade the protective matrix using the iron oxide NPs. They can be precisely moved, using a magnetic field, to mechanically remove the biodegraded biofilms. This is the first time that the three activities have been achieved simultaneously for complete biofilm eradication.
Is this something that dentists might one day be able to implement into their practice?Yes, it could be used as dental prophylaxis and for therapy involving bacterial biofilm infection, including root canal therapy. Because of the versatility of the robotic system, it can be also used to clean dental equipment, particularly water lines, which are susceptible to biofilm build-up. For the latter, we have shown proof of concept of 3D-shaped microrobots breaking biofilm clogs or biofilm formed around curved surfaces [see paper and videos].
Current approaches used by dental professionals to remove biofilm include chemical treatment such as antimicrobial or antiseptic rinsing, and manual removal or scraping of plaque biofilms using dental instruments such as polishers and scalers. The efficacy and efficiency of prophylaxis could be significantly improved using the robotic system.
What are some of the major benefits of using such a system?
For dental applications, robots could greatly facilitate plaque biofilm treatment and removal. There would be no need for laborious manual removal of plaque by scraping or the manual application of chemicals such as antimicrobials to kill bacteria. The robots can be controlled tether-free to precisely kill and degrade the plaque biofilm and simultaneously remove any biodegraded debris without damaging nearby host tissue.
Existing treatments are ineffective because they are incapable of simultaneously degrading the protective matrix, killing the embedded bacteria and physically removing the biodegraded products.
We envision programing microrobots to perform automated cleaning precisely where bacteria accumulate and cause oral disease. This could help clinicians and patients manage and maintain oral health.
This project was a cross-disciplinary partnership including dentists, biologists and engineers. What’s next for the team?
We have demonstrated proof of concept of feasibility and efficacy for biofilm killing and removal in the laboratory and demonstrated practical applications for biofilm cleaning using actual human teeth. We are now optimizing our system for clinical applications, including prototyping devices that use these microrobots for biofilm removal on a variety of surfaces.
Next, we need to conduct in vivo and clinical testing. After that, I think an anti-biofilm robotic system may be available within a couple years or sooner, depending on the technological advancements in this area. We need to show clinical efficacy and then develop prototypes that are practical for in-office use.