Biofilm Inhibition in Oral Pathogens by Nanodiamonds​

Principal Investigator: Dr. Zhiqin Chu, Assistant Professor (Department of Electrical and Electronic Engineering, Joint Appointment with School of Biomedical Sciences)

This project is showcased as the Research Highlight (2022 June-July) in the inaugural exhibition – Engineering for Better Living in Innovation Wing Two

Project information


Complex microbial communities, e.g., biofilms residing in our oral cavity, have recognized clinical significance, as they are typically the main cause for infections. Diamond nanoparticles, namely, nanodiamonds (NDs) have been demonstrated to work as an effective antibacterial agent against planktonic cells (free-floating state) due to their many promising physico-chemical properties. However, little is known about the behaviors of NDs against biofilms (sessile state).

Novelty of the Project

To understand the physical origin of abnormal embryo elongation, we developed a dynamic model (within the framework of continuum mechanics and thermodynamics) to

  1. elucidate how cellular anisotropy and plasticity are gradually developed in the embryo wall during its elongation;
  2. show how the elongation process is sustained and stabilized by the development of anisotropy and plasticity in cells;
  3. reveal that insufficient myosin activity and excessive severing of F-actin bundles are two major causes for abnormal embryo elongation.

Benefit to the Community

This study is expected to be useful for biologists, biophysicists, and biomedical engineers. Specifically,

  1. by elucidating the exact roles of intra/inter-cellular contraction, F-actin realignment and severing/re-bundling in the elongation of embryos, this work significantly advances our physical understanding of this important process;
  2. our study also indicates that abnormal embryo elongation might be rescued by restoring myosin activity and F-actin stability. This could provide new insights for the prevention and treatment of birth defects and related diseases in the future.

About the scholar

Dr. Chu received his B.S. and PhD degrees all in Physics from Northwest University (China) and The Chinese University of Hong Kong, in July 2008 and July 2012, respectively. After one year as postdoctoral fellow in the same group, Dr. Chu carried out his postdoctoral research (2014/04-2016/09) at The University of Stuttgart (Germany). Dr. Chu moved back to Hong Kong in October 2016 and worked as a Research Assistant Professor in Department of Physics at The Chinese University of Hong Kong. Since November 2018, Dr. Chu has been an Assistant Professor in Department of Electrical and Electronic Engineering (Joint Appointment with School of Biomedical Sciences) at The University of Hong Kong. Dr. Chu received the Chen Ning Yang Scholarship from The Chinese University of Hong Kong in 2012, and also The Finalist of Hong Kong Young Scientist Awards (under physics track) from The Hong Kong Institution of Science in 2013.

Project poster
Project images
Dr Prasanna Neelakantan and Dr Chu Zhiqin
NDs work as an effective agent against both free-floating cells (planktonic cells) and attached cells (biofilm) of bacteria and fungi that are highly relevant in oral and systemic infections
Biofilm formed by bacteria and fungi attaching to tooth surfaces
Press release

HKU Engineering and Dentistry collaborative study reveals Nanodiamonds to be an effective agent in tackling oral infections

The press release article can be founded in HKU Press release (

Diamonds are precious stones used for jewelleries and industrial purposes. But in the not-too-distant future, diamond nanoparticles, or nanodiamonds (NDs), may become the solution to everyone’s oral health.

Oral diseases such as dental caries (decay), gum diseases and fungal infections are major global health care problems, resulting in expenditures of millions of dollars every year and yet, have no established solutions. Complex microbial communities, typically occurring as disease-causing bacteria and fungi attaching to teeth surfaces and forming biofilm communities, are the main causes of infections. The National Institutes of Health states that 65-80% of all human infections are formed by biofilms.

In a journal article published in Biomaterials Science titled “Biofilm inhibition in oral pathogens by nanodiamonds”, scientists from the Faculty of Engineering and the Faculty of Dentistry of the University of Hong Kong (HKU) revealed for the first time the inhibitory effect on oral pathogenic biofilms by high-pressure high-temperature (HPHT) NDs.

Co-Principal Investigators of the study Dr Chu Zhiqin, Assistant Professor of the Department of Electrical and Electronic Engineering; and Dr Prasanna Neelakantan, Clinical Assistant Professor in Endodontics revealed that NDs work as an effective agent against both free-floating cells (planktonic cells) and attached cells (biofilm) of bacteria and fungi that are highly relevant in oral and systemic infections. In particular, they uncovered the role of NDs in inhibiting biofilm formation and their disrupting effect on preformed biofilms in several selected orally and systemically important organisms.

Dental caries is one of the most common diseases to affect humankind, affecting more than 3 billion people (48% of the population) worldwide. It is caused by a dominance of acid-producing bacteria that form biofilms on the surface of the teeth. Streptococcus mutans (S. mutans), a Gram-positive bacterium, is considered pivotal for the onset of this disease. Periodontal (gum) disease, which is the sixth most prevalent disease in humans with a global prevalence of 11.2%, is induced by Porphyromonas gingivalis (P. gingivalis), a Gram-negative bacterium. Notably, microbial dysbiosis in the oral cavity has been linked to systemic diseases such as obesity, Alzheimer’s and cardiovascular diseases. These microbials show high resistance to conventional antibiotics, and alternatives including nanotechnology are being intensively explored to provide more efficient therapeutics.

Moreover, fungal infections, another major oral disease with recognised clinical significance, have seen no advancement in the development of therapeutic drugs over the past several decades.

“Nano-materials are the hot topic in current materials science as these ultra-small particles can effectively penetrate into microorganisms and can also be used to carry a wide variety of drugs. Our research showed that these ultra-small nanodiamonds can manipulate genetic mechanisms in the pathogens and prevent their attachment to any surface, hence inhibiting biofilm formation in the oral cavity,” explained Dr Chu and Dr Neelakantan.

“The results of this exciting study demonstrated the great potential of NDs as an alternative therapeutic platform to prevent and treat oral infections. NDs possess many promising features including excellent biocompatibility and flexible surface properties. They are also proven to be very safe for humans. Our work will promote a better mechanistic understanding of NDs on oral pathogens, paving the way for their clinical and translational applications,” they added.

This knowledge and impact of NDs can also be translated to prevent other life-threatening infections in the body, in particular as antifungal drugs, for those vulnerable to fungal infections including very old and very young people, and those who are immunocompromised due to diseases such as HIV infections and diabetes, chronic users of steroids, and cancer patients undergoing chemotherapy. Since fungal cells are very similar to human cells, developing antifungal agents that are not harmful to humans has always been a major challenge.

Details of the published paper:
Biofilm inhibition in oral pathogens by nanodiamonds. 
Tongtong Zhang, Shanthini Kalimuthu, Vidhyashree Rajasekar, Feng Xu, Yau Chuen Yiu, Tony K. C. Hui, Prasanna Neelakantan and Zhiqin Chu.
Biomaterial Science, Issue 15, 2021

Media enquiries: 
Ms Celia Lee, Faculty of Engineering, HKU (Tel: 3917 8519; Email:
Ms Melody Tang, Faculty of Dentistry, HKU (Tel: 2859 0494; Email:

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