An odourless antimicrobial coating invented in a UWindsor lab shows promise to neutralize bacteria in its tracks.

Scientists in chemistry and biochemistry professor John Trant’s team brainstormed the product during the early days of the pandemic. Senior post-doctoral researcher Abhinandan (Ronnie) Banerjee says the combination of materials is physically damaging to bacteria in such a way that antibiotic resistance will not develop.

“We were looking at research opportunities to develop materials that cleanse surfaces with the idea that you apply something once and don’t worry about it for a number of days versus bleach, which you have to constantly wipe,” says Dr. Banerjee.

They combined ionic liquids, compounds completely composed of ions with a melting point below 100°C, and copper nanoparticles.

“I realized they were structurally similar to surfactants like soap and detergent and the liquid can stabilize nanoparticles so combining these two materials is like a double headed warhead,” they said.

“Ionic liquids bore into bacterial walls making them porous and toxic payload nanoparticles go through the perforated walls ­— damaging and crushing them.”

PhD student Sima Dehghandokht tested the product against common bacteria Staphylococcus aureus (the same bacteria is often known as drug-resistant MRSA) and Escherichia coli (E-coli).

“This coating killed off the bacteria,” says Dehghandokht.

“We tried different concentrations of ionic liquid and did some microdilution then got the concentration that was very effective against bacteria, which was interestingly a low concentration.”

The team published their results in the online journal RSC Sustainability, in an article titled “Lethal weapon IL: a nano-copper/tetraalkylphosphonium ionic liquid composite material with potent antibacterial activity”.

Banerjee says Dehghandokht’s research confirmed the ionic liquids worked to rip through bacteria. But that was half the story, they wanted to add copper nanoparticles and to find out what was happening to those nanoparticles in real-time, the team turned to the Canadian Light Source in Saskatoon, Saskatchewan.

“We teamed up with Prof. Pierre Kennepohl from the University of Calgary who had access to the beam, and they saw the nanoparticles gradually falling apart over time,” says Banerjee.

“It turns out the nanoparticles are initially too big to do bacteria any harm — what is really effective is that they degrade.”

The system of combining materials, says Banerjee, is really bad news for bacteria.

“The ionic liquid has the right sized chains to dig into bacteria and rip their walls apart and the copper nanoparticles fall apart easily which release toxic payloads.”

The antibacterial activity was found to increase over time instead of decreasing like happens in many products. Next up, the team would like to find out how long antibacterial activity lasts so they would know how often the product would need to be reapplied.

“This could be invaluable when it comes to contaminated places like hospitals where they must sanitize regularly,” says Dehghandokht.

“From elevator buttons to stair rails, they wouldn’t need to sanitize every five minutes and they could avoid bleach or ethanol, which people can be allergic to.”

To ensure the coating material is safe to touch, the researchers will conduct tests using a human skin mimic generated by the lab’s 3D bioprinter.

“It is a scientist’s dream that their research becomes a product people can use,” says Banerjee.

—Sara Elliott