Diamonds have long been one of the most beloved gemstones of jewellery makers – from engagement rings, intricate necklaces, to elaborate earrings. These precious stones emit a unique, ethereal beauty dazzling all of us. Beyond their gleam, though, diamonds may become the solution to everyone’s oral health. 

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 have revealed that diamond nanoparticles, or nanodiamonds (NDs), are effective agents 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.

Oral Diseases

Despite oral diseases like dental caries (decay), gum diseases and fungal infections being major global healthcare problems which resulted in expenditures of millions of dollars every year, there are no established solutions to tackle these diseases. 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. In fact, The National Institutes of Health states that 65-80% of all human infections are formed by biofilms.

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.

Meanwhile, 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.

Medical Breakthrough

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 for the first time the inhibitory effect on oral pathogenic biofilms by high-pressure high-temperature (HPHT) NDs.

“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 result of this study demonstrates the immense potential of NDs as an alternative therapeutic platform to prevent and treat oral infections since NDs possess many promising features, which includes 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.

Since fungal cells bear a close resemblance to human cells, developing antifungal agents unharmful to humans has always been a major challenge. But with this newly-gained knowledge of NDs, it opens up countless opportunities for future applications of NDs into clinical practices that may prevent other life-threatening infections in the body. They may serve particularly as antifungal drugs for those vulnerable to fungal infections, like young and elderly people, and those who are immunocompromised due to HIV infections and diabetes, or chronic users of steroids and cancer patients undergoing chemotherapy.

To learn more about the research findings, please check out the journal paper published in Biomaterial Science here.

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