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Nanoparticles Provide Novel Way to Apply Drugs to Dental Plaque

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

Therapeutic agents intended to reduce dental plaque and prevent tooth decay are often removed by saliva and the act of swallowing before they can take effect. But a team of researchers has developed a way to keep the drugs from being washed away. Dental plaque is made up of bacteria enmeshed in a sticky matrix of polymers—a polymeric matrix—that is firmly attached to teeth. The researchers, led by Danielle Benoit at the University of Rochester and Hyun Koo at the University of Pennsylvania’s School of Dental Medicine, found a new way to deliver an antibacterial agent within the plaque, despite the presence of saliva. To deliver the agent—known as farnesol—to the targeted sites, the researchers created a spherical mass of particles, referred to as a nanoparticle carrier. They constructed the outer layer out of cationic—or positively charged—segments of the polymers. For inside the carrier, they secured the drug with hydrophobic and pH-responsive polymers.

The positively-charged outer layer of the carrier is able to stay in place at the surface of the teeth because the enamel is made up, in part, of HA (hydroxyapatite), which is negatively charged. Just as oppositely charged magnets are attracted to each other, the same is true of the nanoparticles and HA. Because teeth are coated with saliva, the researchers weren’t certain the nanoparticles would adhere. But not only did the particles stay in place, they were also able to bind with the polymeric matrix and stick to dental plaque. Since the nanoparticles could bind both to saliva-coated teeth and within plaque, Benoit and colleagues used them to carry an anti-bacterial agent to the targeted sites.