Graphene and Nanoparticles Might Offer High-Tech Help for Your Choppers

Nanotechnology advances might soon be giving people with an upcoming dental appointment something to smile about. Scientists have published two studies focused on deploying either nanoparticle assemblies or graphene to control the bacteria that attack teeth.

Both materials have shown promise to dramatically slow tooth decay, cavity formation and gum disease, and one even offers a defense against antibiotic resistant bacteria.

The first possibility comes from the University of Rochester and the University of Pennsylvania, where researchers have figured out a way to keep an antibacterial compound on teeth after eating and being washed with saliva.

The team developed a carrier for the compound called farnesol, which kills bacteria and slows biofilm formation on teeth but is washed away by saliva and swallowing. Individual polymer nanoparticles comprise the spherical carrier and act as a shell surrounding the farnesol molecules. This shell’s outer layer is attracted to one of the constituents of tooth enamel, hydroxyapatite, and stays put when saliva washes over the teeth. At the same time, the shell’s therapy-containing inner layer, is built to dissolve in acidic environments like those created by the bacteria that make up dental plaque.

To try out whether the drug and carrier package worked as they thought it should, they applied it to the teeth of lab rats that were given a species of tooth-decay-causing bacteria.

“We applied the test solutions to rats’ mouths twice daily for 30 seconds, simulating what a person might do using a mouth rinse morning and night,” said University of Pennsylvania orthodontics professor Hyun Koo, who was co-senior author of the work that was published in the journal ACS Nano.“When the drug was administered without the nanoparticle carriers, there was no effect on the number of cavities and only a very small reduction in their severity. But when it was delivered by the nanoparticle carriers, both the number and severity of the cavities were reduced.”

The researchers said their work could potentially lead to temporary or permanent coatings that prevent dental bacteria from colonizing teeth.

“Farnesol-loaded nanoparticles effectively attenuated biofilm virulence in vivo using a clinically relevant topical treatment regimen (2×/day) in a rodent dental caries disease model,” the authors wrote. “Strikingly, treatment with farnesol-loaded nanoparticles reduced both the number and severity of carious lesions, while free farnesol had no effect. Nanoparticle carriers have great potential to enhance the efficacy of antibiofilm agents through multitargeted binding and pH-responsive drug release due to microenvironmental triggers.”



(Farnesol is released from the nanoparticle carriers into the cavity-causing dental plaque. Graphic courtesy of Michael Osadciw/University of Rochester.)

Meanwhile, scientists in China reported in the journal Applied Materials & Interfaces that they found success using a compound containing the supermaterial graphene, an atom-thick sheet of bonded carbon atoms with a range of useful properties. One of those is antibiotic activity that seems to work even on organisms that have grown resistant to antibiotics.

In their initial study, they applied nanosheets made of graphene oxide molecules to dental pathogens. The material promptly poked holes in the bacterial cell walls, causing their internal contents to leak out and kill the organism. Previous work has indicated that graphene selectively targets bacterial cells and causes minimal harm to mammalian cells, according to the American Chemical Society.

(Graphene oxide nanosheet destruction of bacterial cell walls, causing internal contents to leak out and killing the organism. Image courtesy He et al./ACS Appl. Mater. Interfaces.)

“Dental caries and periodontal diseases have a close relationship with microbes such as Streptococcus mutans, Porphyromonas gingivalis and Fusobacterium nucleatum,” the authors wrote.

“We found GO nanosheets were highly effective in inhibiting the growth of dental pathogens…GO nanosheets would be an effective antibacterial material against dental pathogens and the potential applications in dental care and therapy are promising,” they concluded.



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