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Nanoparticle Process Designed to Detect, Treat Oral Bacteria

Streptococcus mutans

Streptococcus mutans bacterial communities (

17 August 2018. A bioengineering lab devised a way to quickly detect and treat bacteria responsible for tooth decay with a combination of X-rays and a non-toxic compound in nanoscale particles. Researchers from University of Illinois in Urbana describe their techniques in the 30 July issue of the journal Biomaterials (paid subscription required).

A team from the Materials in Medicine lab at Illinois, led by engineering professor Dipanjan Pan, is seeking faster and more reliable methods for identifying and fighting harmful bacteria in the mouth that form stubborn communities called biofilms and contribute to cavities and tooth decay. Many dentists today use tablets that dissolve in the mouth or apply swabs with agents that disclose bacterial plaques, but these methods do not generally distinguish between harmful and benign bacteria. As Pan describes it in a university statement, “detection of dental plaque is highly subjective and only depends on the dentist’s visual evaluation.”

The Illinois team aims to take the subjectivity out of the process. Their technique uses hafnium oxide, an inert stable compound used in glass and ceramics, formulated in nanoscale particles. The hafnium oxide binds to characteristic peptides in offending bacteria, such as Streptococcus mutans, the most common cavity-causing oral microbe. The hafnium oxide enhances the visual presence of S. mutans bacteria, when exposed to a probe with ordinary X-rays, like those found in most dental clinics. At the same time, benign microbes are left alone.

In larger quantities, the hafnium oxide nanoparticles also show antibacterial properties. The nanoparticles not only bind to the bacteria, but when applied in higher concentrations, they also fragment the bacterial DNA, killing the microbes. In lab tests first with extracted teeth and later in lab rats, daily doses of hafnium oxide nanoparticles stopped the growth of S. mutans biofilms for 8 days. The researchers envision dentists first applying small quantities of hafnium oxide nanoparticles in a first step to identify the harmful bacteria with X-rays, then follow-up with a larger dose to break up the biofilms.

Pan says in this case the antimicrobial technique used by hafnium oxide nanoparticles to fragment bacterial DNA on tooth surfaces works differently from typical antibiotics. He notes,”This mechanism sets our work apart from previously pursued nanoparticle-based approaches where the medicinal effect comes from antibiotics encapsulated in the particles.” He also adds that “our approach avoids antibiotic resistance issues and it’s safe and highly scalable, making it well-suited for eventual clinical translation.”

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