Applying tea tree oil or other natural plant extracts as a coating for medical devices could prevent millions of bacterial infections each year, according to researchers from James Cook University in Australia.

The discovery comes at a time when an increasing number of unplanned surgeries are performed to fight infections caused by biofilm, a thin layer of bacteria that forms on the surface of medical devices.

Such bacteria is thought to account for 80 percent of worldwide surgery-associated infections, which results in approximately 550,000 deaths each year.

Now, the researchers have developed a technique to convert essential oils and herb extracts into polymer coatings that can prevent biofilm bacteria from ever being formed.

The study is published in the journal Polymers.

Antibiotic properties of plant extracts

Led by Mohan Jacob, a professor in the JCU’s College of Science and Engineering, the team turned to extracts from Plant Secondary Metabolites, or PSMs, to fight bacteria.

PSMs are a low-cost, environmentally-friendly resource that can be used to fight bacteria similarly to antibiotics, according to Jacob.

“They’re derived from such things as essential oils and herb extracts and they have relatively powerful broad-spectrum antibacterial activities,”Jacob said in a statement. “PSMs are a low-cost renewable resource available in commercial quantities, with limited toxicity, and potentially, different mechanisms for fighting bacteria than synthetic antibiotics.”

Though the researchers looked into many types of PSMs, the team has mostly been focused on the Australian-based essential oil, tea tree oil.

Creating a coating

Since PSMs are derived in the form of a liquid, the researchers had to develop a way to convert them into solids so they could be used as a coating on medical devices.

To do this, Jacob explained, they create a volatile gas from the liquid and pass it through a high-energy electromagnetic field, where the chemical bonds break down and join with another molecule to form a polymer.

This process allows the researchers to convert the extracts without introducing additional chemicals that could potentially be harmful to the coating.

“The main advantage of this approach is that we are not using other chemicals, such as solvents, during the fabrication process,” Katia Bazaka, an adjunct senior research fellow in the College of Science and Engineering, said in a statement. “As such, there is no threat of potentially harmful chemicals being retained in the coating or them damaging the surface of the material onto which the coating is applied. It also makes the fabrication process more environmentally friendly.”

So far, the researchers have successfully creating coatings that can prevent the formation of commonly found bacteria, including pseudomonas aeruginosa and staphylococcus.

“The coatings are very good to prevent biofilm formation on different surfaces,” Jacob said.

Why plants?

JCU is currently the global pioneer in the development of plant-derived polymer films, publishing more than 70 research articles and six Ph.D. theses on the subject.

But why focus on plants?

For one, the overuse of synthetic antibiotics has gradually made them less effective to fight bacteria. Scientists believe that if new strategies to fight infection aren’t developed soon, we could retreat to an era where minor infections could result in major medical emergencies.

And since a variety of plants and plant-based extracts offer natural, antibiotic properties, it seems to be an obvious solution.

“It is always important to develop better antibacterial coatings and hence reduce the rate of infection,” said Jacob.

Future developments

The team is currently working to test the coatings on additional types of bacteria, and is collaborating with researchers from the JCU-based Australian Institute of Tropical Health and Medicine.

In addition, the work has also been extended to target marine organisms to prevent the growth of biofilms on aquatic sensors and their subsequent failure.

“Another attractive feature of these coatings is their optical transparency, which may be quite important if you are using them to coat contact lenses, or optical windows in aquatic sensors,” said Ian Atkinson, director of JCU’s eResearch unit, who collaborated on the research.