Biofilms—structured communities of microorganisms that create a protective matrix shielding them from external threats, including antibiotics—are responsible for about 80% of human infections and present a significant challenge in medical treatments, often resisting conventional methods.
In a Q&A with Penn Today, Hyun (Michel) Koo of the School of Dental Medicine and Edward Steager of the School of Engineering and Applied Science at Penn discuss an innovative approach they’ve partnered on: the use of small-scale robotics, microrobots, to offer a promising solution to tackle these persistent infections, bringing new capabilities and precision to the field of biomedical engineering.
Q: What is the motivation behind opting for tiny robots to tackle infections?
Koo: Treating biofilms is a broad yet unresolved biomedical problem, and conversely, the strategies for tackling biofilms are limited for a number of reasons. For instance, biofilms typically occur on surfaces that can be tricky to reach, like between the teeth in the oral cavity, the respiratory tract, or even within catheters and implants, so treatments for these are usually restricted to antibiotics (or antimicrobials) and other physical methods reliant on mechanical disruption. However, this touches on the problem of antimicrobial resistance: targeting specific microorganisms present in these structures is difficult, so antibiotics often fail to reach and penetrate the biofilm’s protective layers, leading to persistent infections and increased risk of antibiotic resistance.
We needed a way to circumvent these constraints, so Ed and I teamed up in 2017 to develop new, more precise and effective approaches that leverage the engineers’ ability to generate solutions that we, the clinicians and life science researchers, identify.
Hyun (Michel) Koo is a professor in the Department of Orthodontics and in the divisions of Pediatric Dentistry and Community Oral Health and the co-founder of the Center for Innovation & Precision Dentistry in the School of Dental Medicine at the University of Pennsylvania. He is a member of the Penn Bioengineering Graduate Group.
Edward Steager is a senior research investigator in Penn’s School of Engineering and Applied Science.
Michel Koo of the School of Dental Medicine and David Cormode of the Perelman School of Medicine and the School of Engineering and Applied Science led a team of researchers that uncovered a way to combine two FDA-approved treatments to treat tooth decay that taps into the blend’s bacteria-killing capabilities without disrupting the mouth’s microbiome. (Image: iStock / Alex Sholom)
The sting of a toothache or the discovery of a cavity is a universal dread. Dental caries, more commonly known as tooth decay, is an insidious adversary, taking a toll on millions of mouths worldwide. Caries can lead to pain, tooth loss, infection, and, in severe cases, even death.
While fluoride-based treatments have long been the gold standard in dentistry, this singular approach is now dated and has limited effect. Current treatments do not sufficiently control biofilm—the main culprit behind dental caries—and prevent enamel demineralization at the same time. This dual dilemma becomes particularly pronounced in high-risk populations where the onset of the disease can be both rapid and severe.
“Traditional treatments often come short in managing the complex biofilm environment in the mouth,” Koo, senior co-author on the study, says. “Our combined treatment not only amplifies the effectiveness of each agent but does so with a lower dosage, hinting at a potentially revolutionary method for caries prevention in high-risk individuals.”
David Cormode is an associate professor of radiology and bioengineering with appointments in Penn’s Perelman School of Medicine and School of Engineering and Applied Science.
Other authors are Yue Huang, Nil Kanatha Pandey, Shrey Shah, and Jessica C. Hsu of Penn’s Perelman School of Medicine; Yuan Liu, Aurea Simon-Soro, Zhi Ren, Zhenting Xiaang, Dongyeop Kim, Tatsuro Ito, Min Jun Oh, and Yong Li of Penn’s School of Dental Medicine; Paul. J Smeets, Sarah Boyer, Xingchen Zhao, and Derk Joester of Northwestern University; and Domenick T. Zero of Indiana University.
The work was supported by the National Institute of Health (grants R01-DE025848 and TL1TR001423 and awards S10OD026871 and R90DE031532) and the National Science Foundation (awards ECCS-2025633 and DMR-1720139).
Kathleen J. Stebe and Michel Koo urge “the academic community to adopt a coordinated approach uniting dental medicine and engineering to support research, training and entrepreneurship to address unmet needs and spur oral health care innovations.” (Image: Min Jun Oh and Seokyoung Yoon)
Penn’s Center for Innovation & Precision Dentistry (CiPD) is the first cross-disciplinary initiative in the nation to unite oral-craniofacial health sciences and engineering.
In just two years since CiPD was founded, the outcomes of this newly conceived research partnership have proven its value: microrobots that clean teeth for people with limited mobility, a completely new understanding of bacterial physics in tooth decay, enzymes from plant chloroplasts that degrade plaque, promising futures for lipid nanoparticles in oral cancer treatment and new techniques and materials to restore nerves in facial reconstructive surgery.
In addition, CiPD is training the next generation of dentists, scientists and engineers through an NIH/NIDCR-sponsored postdoctoral training program as well as fellowships from industry.
The center’s Founding Co-Directors, Kathleen J. Stebe, Richer & Elizabeth Goodwin Professor in Chemical and Biomolecular Engineering, and Michel Koo, Professor of Orthodontics in Penn Dental Medicine, published an editorial in the Journal of Dental Research, planting a flag for CiPD’s mission and encouraging others to mirror its method.
The two urge “the academic community to adopt a coordinated approach uniting dental medicine and engineering to support research, training and entrepreneurship to address unmet needs and spur oral health care innovations.”
Kyle Vining, who is jointly appointed in the School of Dental Medicine and the School of Engineering and Applied Science, hopes that his research will help to push forward the state of clinical dentistry.
“During my training, I saw that there was overlap where I could do clinical work and science at the same time, and so that’s what I’ve been doing ever since,” Vining says. “As far back as middle school, I always wanted to be a biomedical engineer, and then the clinical side became interesting to me because I didn’t want to only do the theoretical or research side of things. I also wanted the hands-on, practical interaction of a skilled profession.”
The benefits of a dual career: Variety and opportunities to give back
Vining finds that wearing two hats offers the best of both worlds: opportunities to help both individual patients and to contribute to scientific and clinical progress.
“On the dentistry side, what I enjoy is getting to see patients, solving clinical problems, and trying to perform the best treatment I can; it has this rapid pace, which is kind of exciting and keeps you motivated,” Vining says. “And then research allows me to explore my interests and think about making an impact more broadly, not just in dentistry, but in medicine or in the world in general.”
Vining says dental school was demanding, yet a good time to explore his varied interests. He says he’d encourage others to pursue dentistry with an interdisciplinary approach. “Having exposure to different fields or different knowledge while you’re a student is really good for students and the profession in general,” he says.
The path towards a dual career
Vining first delved into research as a biomedical engineering undergraduate at Northwestern University. “I had the opportunity to work in a materials science lab studying the chemistry of surfaces. We would use molecules to modify the properties and surfaces that environments or cells could interact with,” he says.
Then, as a student at the University of Minnesota School of Dentistry, Vining realized that this same materials science research had many applications in dentistry. While in dental school, Vining conducted independent research in a materials science lab and also took the opportunity to do a yearlong fellowship in a cell and developmental biology lab at the National Institutes of Health.
Vining credits this fellowship with launching him towards a Ph.D., which he completed in bioengineering at Harvard in 2020. After earning his Ph.D., Vining conducted research at the Dana-Farber Cancer Institute prior to joining Penn.
Using biomaterials to understand how cells and tissues interact
Vining’s research at Penn aims to understand how the biophysical properties of materials impact cellular processes such as inflammation and fibrosis.
“Fibrosis is a physical change in tissues that produces a scar-like matrix that can inhibit healing, impair cancer treatment, and in general is not compatible with tissues regeneration,” Vining says. “There’s been a lot of effort on antifibrotic drugs, but we’re trying to look at fibrosis a little bit differently. Instead of directly inhibiting fibrosis, we’re trying to understand its consequences for the immune system because the immune system can be hijacked and become detrimental for your tissues.”
Through a better understanding the feedback loop between fibrotic tissue and the immune system, Vining hopes to design interventions to facilitate wound healing and tissue remodeling during restorative dental procedures and for treating diseases including head and neck cancer.
He’s also investigating how biomaterials like the resin used in tooth fillings interact with dental tissues. “Dental fillings rely on decades-old technologies that have been grandfathered in and contain toxic monomers that are not safe for biological systems,” Vining says. “We found a biocompatible resin chemistry that supports cells in vitro, and we’re trying to apply this to new types of dental fillings that promote repair or generation of dental tissues.”
Fostering interdisciplinary collaborations at Penn
“Dr. Vining is an ideal fit for the vision and mission of the CiPD,” says Penn Dental’s Hyun (Michel) Koo, co-founder and co-director of the CiPD. “With a secondary appointment in the School of Engineering, he will be instrumental in continuing to strengthen our engineering collaborations and teaching our students to work across disciplines to advance research, training, and entrepreneurship in this realm.”
Ultimately, Vining says it was Penn’s scientific community and the opportunities for interdisciplinary collaborations that drew him here.
“It was very apparent that there were a lot of potential research paths to pursue here and a lot of opportunities for collaborations,” Vining says. “One of the most exciting things for me so far has been meeting with faculty, whether it’s at Penn Medicine, the School of Engineering, Wharton, Penn Dental, or the Veterinary School. These meetings have already opened up new projects and collaborations.”
The collaboration sparked when Vining saw Mitchell present on a new technology that uses lipid nanoparticles to bind and target bone marrow cells at the 2022 CiPD first annual symposium. “It got me thinking because the dentin inside of teeth is a mineralized tissue very similar to bone, and the pulp inside the dentin is analogous to bone marrow tissue,” Vining says.
Collaborating researchers from the University of Pennsylvania School of Dental Medicine and the Adams School of Dentistry and Gillings School of Global Public Health at the University of North Carolina have discovered that a bacterial species called Selenomonas sputigena can have a major role in causing tooth decay.
Scientists have long considered another bacterial species, the plaque-forming, acid-making Streptococcus mutans, as the principal cause of tooth decay—also known as dental caries. However, in the study, published in Nature Communications, the Penn Dental Medicine and UNC researchers showed that S. sputigena, previously associated only with gum disease, can work as a key partner of S. mutans, greatly enhancing its cavity-making power.
“This was an unexpected finding that gives us new insights into the development of caries, highlights potential future targets for cavity prevention, and reveals novel mechanisms of bacterial biofilm formation that may be relevant in other clinical contexts,” says study co-senior author Hyun (Michel) Koo, a professor in the Department of Orthodontics and Divisions of Pediatrics and Community Oral Health and co-director of the Center for Innovation & Precision Dentistry at Penn Dental Medicine.
The other two co-senior authors of the study were Kimon Divaris, professor at UNC’s Adams School of Dentistry, and Di Wu, associate professor at the Adams School and at the UNC Gillings School of Global Public Health.
“This was a perfect example of collaborative science that couldn’t have been done without the complementary expertise of many groups and individual investigators and trainees,” Divaris says.
Michel Koo is a professor in the Department of Orthodontics and divisions of Community Oral Health and Pediatric Dentistry in Penn Dental Medicine and co-director of the Center for Innovation & Precision Dentistry. He is a member of the Penn Bioengineering Graduate Group.
Candida albicans is a species of yeast that is a normal part of the human microbiota but can also cause severe infections that pose a significant global health risk due to their resistance to existing treatments, so much so that the World Health Organization has highlighted this as a priority issue. The picture above shows a before (left) and after (right) fluorescence image of fungal biofilms being precisely targeted by nanozyme microrobots without bonding to or disturbing the tissue sample. (Image: Min Jun Oh and Seokyoung Yoon)
Infections caused by fungi, such as Candida albicans, pose a significant global health risk due to their resistance to existing treatments, so much so that the World Health Organization has highlighted this as a priority issue.
Although nanomaterials show promise as antifungal agents, current iterations lack the potency and specificity needed for quick and targeted treatment, leading to prolonged treatment times and potential off-target effects and drug resistance.
“Candida forms tenacious biofilm infections that are particularly hard to treat,” Koo says. “Current antifungal therapies lack the potency and specificity required to quickly and effectively eliminate these pathogens, so this collaboration draws from our clinical knowledge and combines Ed’s team and their robotic expertise to offer a new approach.”
The team of researchers is a part of Penn Dental’s Center for Innovation & Precision Dentistry, an initiative that leverages engineering and computational approaches to uncover new knowledge for disease mitigation and advance oral and craniofacial health care innovation.
For this paper, published in Advanced Materials, the researchers capitalized on recent advancements in catalytic nanoparticles, known as nanozymes, and they built miniature robotic systems that could accurately target and quickly destroy fungal cells. They achieved this by using electromagnetic fields to control the shape and movements of these nanozyme microrobots with great precision.
“The methods we use to control the nanoparticles in this study are magnetic, which allows us to direct them to the exact infection location,” Steager says. “We use iron oxide nanoparticles, which have another important property, namely that they’re catalytic.”
Other authors include Min Jun Oh, Alaa Babeer, Yuan Liu, Zhi Ren, Zhenting Xiang, Yilan Miao, and Chider Chen of Penn Dental; and David P. Cormode and Seokyoung Yoon of the Perelman School of Medicine. Cormode also holds a secondary appointment in Bioengineering.
This research was supported in part by the National Institute for Dental and Craniofacial Research (R01 DE025848, R56 DE029985, R90DE031532 and; the Basic Science Research Program through the National Research Foundation of Korea of the Ministry of Education (NRF-2021R1A6A3A03044553).
Members of the inaugural cohort of fellows in the Center for Innovation and Precision Dentistry (CiPD)’s NIDCR T90/R90 Postdoctoral Training Program have been recognized for their research activities with fellows receiving awards from the American Association for Dental, Oral, and Craniofacial Research (AADOCR), the Society for Biomaterials, and the Osteology Foundation. All four of the honored postdocs are affiliated with Penn Bioengineering.
Zhi Ren
Zhi Ren won first place in the Fives-Taylor Award at the AADOCR Mini Symposium for Young Investigators. A postdoctoral fellow in the labs of Dr. Hyun (Michel) Koo at Penn Dental Medicine (and member of the Penn Bioengineering Graduate Group) and Dr. Kathleen Stebe of Penn Engineering, Dr. Ren’s research focuses on understanding how bacterial and fungal pathogens interact in the oral cavity to form a sticky plaque biofilm on teeth, which gives rise to severe childhood tooth decay that affects millions of children worldwide. In his award-winning study, titled “Interkingdom Assemblages in Saliva Display Group-Level Migratory Surface Mobility”, Dr. Ren discovered that bacteria and fungi naturally present in the saliva of toddlers with severe decay can form superorganisms able to move and rapidly spread on tooth surfaces.
Justin Burrell
Justin Burrell won second place in the AADOCR Hatton Competition postdoctoral category for his research. Dr. Burrell has been working with Dr. Anh Le in Penn Dental Medicine’s Department of Oral Surgery/Pharmacology and Dr. D. Kacy Cullen of Penn Medicine and Penn Bioengineering. Together, their interdisciplinary team of clinician-scientists, biologists, and neuroengineers have been developing novel therapies to expedite facial nerve regeneration and increase meaningful functional recovery.
Marshall Padilla
Marshall Padilla earned third place at the Society for Biomaterials Postdoctoral Recognition Award Competition for a project titled, “Branched lipid architecture improves lipid-nanoparticle-based mRNA delivery to the liver via enhanced endosomal escape”. Padilla was also a finalist in the AADOCR Hatton Award Competition, presenting on a separate project titled, “Lipid Nanoparticle Optimization for mRNA-based Oral Cancer Therapy”. Both projects employ lipid nanoparticles, the same delivery vehicles used in the mRNA COVID-19 vaccine technology. A postdoctoral fellow in the lab of Dr. Michael J. Mitchell of Penn’s Department of Bioengineering, Dr. Padilla’s research focuses on developing new ways to enhance the efficacy and safety of lipid nanoparticle technology and its applications in dentistry and biomedicine. He has been working in collaboration with Dr. Shuying (Sheri) Yang and Dr. Anh Le in Penn Dental Medicine.
Dennis Sourvanos
Dennis Sourvanos (GD’23, DScD’23) was the recipient of the Trainee Travel Grant award through the Osteology Foundation (Lucerne Switzerland). Dr. Sourvanos will be presenting his research related to medical dosimetry and tissue regeneration at the International Osteology Symposium in Barcelona, Spain (April 27th – 29th 2023). He also presented at the 2023 AADOCR/CADR Annual Meeting for his project titled, “Validating Head-and-Neck Human-Tissue Optical Properties for Photobiomodulation and Photodynamic Therapies.” Dr. Sourvanos has been working with Dr. Joseph Fiorellini in Penn Dental Medicine’s Department of Periodontics and Dr. Timothy Zhu in the Hospital of the University of Pennsylvania’s Department of Radiation Oncology and the Smilow Center for Translational Research (and member of the Penn Bioengineering Graduate Group).
“Through their collaborative research, they are aiming to develop next-generation treatments for dental caries (tooth-decay) using lipid nanoparticles, the same delivery vehicles employed in the mRNA COVID-19 vaccine technology.
‘This project shows the type of innovative ideas and collaborations that we are kickstarting through the IDEA prize,’ says Dr. Michel Koo, co-director of the CiPD and Professor at Penn Dental Medicine. ‘This is a great example of synergistic interaction at the interface of engineering and oral health’ adds Dr. Kate Stebe, co-director of the CiPD and Professor at Penn Engineering.”
An infographic explains the magnetic and catalytic properties of the iron oxide nanoparticles and their assembly into bristle and floss-like forms. (Image: Melissa Pappas/Penn Engineering)
Koo shared findings from one of his recent studies conducted in collaboration with Penn Engineering, which showed that a shapeshifting robotic microswarm can brush and floss teeth.
“Routine oral care is cumbersome and can pose challenges for many people, especially those who have a hard time cleaning their teeth” says Koo. “You have to brush your teeth, then floss your teeth, then rinse your mouth; it’s a manual, multistep process. The big innovation here is that the robotics system can do all three in a single, hands-free, automated way.”
The building blocks of these microrobots are iron oxide nanoparticles that have both catalytic and magnetic activity. Using a magnetic field, researchers could direct their motion and configuration to form either bristlelike structures that sweep away dental plaque from the broad surfaces of teeth, or elongated strings that can slip between teeth like a length of floss.
“Nanoparticles can be shaped and controlled with magnetic fields in surprising ways,” says Edward Steager, a senior research investigator at Penn Engineering and co-corresponding author. “We form bristles that can extend, sweep, and even transfer back and forth across a space, much like flossing. The way it works is similar to how a robotic arm might reach out and clean a surface. The system can be programmed to do the nanoparticle assembly and motion control automatically.”
“Padilla came to the CiPD training program earlier this year with a Ph.D. in Chemistry from the University of Wisconsin-Madison. He is currently a postdoctoral fellow in the lab of Dr. Michael J. Mitchell of Penn’s Department of Bioengineering, where his research focuses on developing new materials to enhance the efficacy and safety of biological therapeutics. While passionate about research, he also has a strong interest in developing mentoring relationships and in teaching. At Wisconsin, Marshall earned a certificate in research, teaching, and learning, in which he conducted a research project on developing positive metacognitive practices in introductory organic chemistry. Additionally, he taught a course on mentoring in a research setting, and is passionate about promoting diversity and inclusiveness in biomedical sciences.”
