Tag Archives: ionic liquid

Skin-penetrating ionic liquids mixed with antibiotics provide better way of killing microbes

Ionic Liquids could become instrumental in treating wound infections or any surfaces affected by biofilms. Image via Wiki Commons.

As microbes become more and more resistant to antibiotics and cleaning products, it’s crucial that we find better, more efficient way of fending them off. Dr. Samir Mitragotri from the University of California at Santa Barbara has led a team which showed that ionic liquids (ILs), also known as liquid salts, dramatically improve the treatment of microbial biofilm skin infections, while also exhibiting antibacterial properties, facilitating deep skin penetration of antibiotics, and displaying a positive safety profile.

Ionic liquids should not be confused with salts dissolved in a liquid. Instead, they are liquids which are composed entirely of paired ions, like for example molten table salt but at room temperature; salt melts at 801 °C (1,474 °F). After trying several ionic liquids, researchers found that choline geranate works best – its efficiency was remarkable, and they decided to use it in future tests.

They tested it on a biofilm-infected wound model. Over 95% of all bacteria were killed after 2 hours of application of choline geranate and a passenger antibiotic cefadroxil. The choline geranate alone was also very effective, killing almost 92% of all bacteria, while the antibiotic alone didn’t kill almost any bacteria due to the biofilm barrier.

Researchers also tested the ionic liquid’s ability to transport substances in the skin. Results showed a huge increase in the transport capacity – 16 times more than without it. There was also no cell irritation or inflammation associated with the treatment.

The importance of this discovery becomes even more obvious when you consider that real life 75% of infections in humans are associated with biofilms.

Biofilm through a microscope. Image via Wiki Commons.

Generally speaking, biofilms are groups of microorganisms in which cells stick to each other on a surface; macroscopically, they are often referred to as ‘slime’ (though not everything called ‘slime’ is a biofilm). Microbes form a biofilm in response to many factors – most commonly in order to better attach to a surface. When they do that, they start excreting gelatinous substance that anchors them even to slippery surfaces – like teeth or sterilized surgical instruments. The biofilm is very resistant to penetration and can spread quite easily; it is also resistant to penetration and can be quite difficult to exterminate – for this reason, the treatment with ionic liquids has massive therapeutic benefits and ultimately, the potential to countless lives,

Tawny crazy ants (Nylanderia fulva) attacked by rivaling fire ants (Solenopsis invicta). To protect itself against the deadly fire ant venom, crazy ants secret a venom of their own that cancels the other. When the two mix, a new substance whose class has never been encountered in nature emerges. Photo: Ed LeBrun

First naturally occuring ionic liquids found in ant venom mix

Tawny crazy ants (Nylanderia fulva) attacked by rivaling fire ants (Solenopsis invicta). To protect itself against the deadly fire ant venom, crazy ants secret a venom of their own that cancels the other. When the two mix, a new substance whose class has never been encountered in nature emerges. Photo: Ed LeBrun

Tawny crazy ants (Nylanderia fulva) attacked by rivaling fire ants (Solenopsis invicta). To protect itself against the deadly fire ant venom, crazy ants secret a venom of their own that cancels the other. When the two mix, a new substance whose class has never been encountered in nature emerges. Photo: Ed LeBrun

Ionic liquids (IL) are basically liquid salts with very low melting points. These are heavily used in industry as solvents for chemical processes or as performance enhancers, part of electrolytes or lubricants. It’s only recently that an ionic liquid has been found to occur in nature, after a team of researchers at University of South Alabama found that the substances forms when two ant species mix their venom.

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The team led by Prof. James Davis was studying two ant species fighting over territory: fire ants (Solenopsis Invicta) and tawny crazy ants (Nylanderia fulva). Fire ants and tawny crazy ants are native to South America, where their battle may have raged for thousands of years. Fire ants arrived in the United States first, sometime in the 1930s. The crazy ants didn’t start to show up until the early 2000s.

When the fire ants would sprinkle the tawny crazies with their venom, the latter would respond by secreting formic acid, their own venom, to groom and rid themselves of the poisonous attack. When the two substances mix, a viscous ionic liquid containing a mixture of different cations along with formate anions forms.

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The properties of the resulting mixed-cation ammonium formate milieu are consistent with its classification as a protic IL.  Seeing how the IL was discovered by accident, it’s very much likely that other naturally occurring ILs might be discovered.

It’s interesting to see how well the crazy ants have adapted to fire ants’ venom. In a separate study, Edward LeBrun, a researcher at the Fire Ant Research and Management Project at the University of Texas at Austin, found when crazy ants were prevented from secreting the antidote after being brushed with a bit of nail polish on their abdomens, 48% of them died when exposed to fire ants. When they were allowed to secrete the antidote, 98% survived.

Finding appeared in the journal Angewandte Chemie International.