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Newswise 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 polymersa polymeric matrixthat is firmly attached to teeth. The researchers, led by Danielle Benoit at the University of Rochester and Hyun Koo at the University of Pennsylvanias School of Dental Medicine, found a new way to deliver an antibacterial agent within the plaque, despite the presence of saliva.

Their findings have been published in the journal ACS Nano.

We had two specific challenges, said Benoit, an assistant professor of biomedical engineering. We had to figure out how to deliver the anti-bacterial agent to the teeth and keep it there, and also how to release the agent into the targeted sites.

To deliver the agentknown as farnesolto the targeted sites, the researchers created a spherical mass of particles, referred to as a nanoparticle carrier. They constructed the outer layer out of cationicor positively chargedsegments 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 werent 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. The researchers then needed to figure out how to effectively release the agent into the plaque.

A key trait of the inner carrier material is that it destabilizes at acidicor low pHlevels, such as 4.5, allowing the drug to escape more rapidly. And thats exactly what happens to the pH level in plaque when its exposed to glucose, sucrose, starch, and other food products that cause tooth decay. In other words, the nanoparticles release the drug when exposed to cavity-causing eating habitsprecisely when it is most needed to quickly stop acid-producing bacteria.

Excerpt from:

A Novel Way to Apply Drugs to Dental Plaque