Caitríona Farrell reports on how Ireland is leading the international research into a new, wide-ranging branch of chemistry that could rid our hospitals of MRSA and our pavements of chewing gum
Chemistry has definitely come a long way from the propositions of the ancient Greek that all matter on Earth was comprised of four elements: wind, fire, earth and water. The elders of ancient Athens obviously forgot to account for the scores of elements that form the modern periodic table. Man has undergone an epic journey of discovery in the intervening years, gaining a better understanding of the natural world and its properties – and learning how to exploit its abilities to ensure a safer and healthier environment for its species. Today, our standard of living has been largely determined by chemistry.
One of the latest hot properties in the world of chemical industries is the research of what are called ‘ionic liquids’, which were discovered as recently as the late 1940s. Frank Hurley and Tom Weir, working at the Rice Institute in Texas, discovered that they could make some salts turn liquid at close to room temperature. They mixed a powdered organic salt known as alkylpyridinium chloride with another salt, aluminium chloride, before gently heating the mixture. They observed that the two powders reacted together quickly and – to their surprise – formed a clean, colourless liquid: the world’s first ionic liquid.
Ionic liquids are a particularly attractive prospect, because of the manner in which the cations and anions can have their physical, chemical, and biological properties modified to cater for whatever specific purpose required. The applications of ionic liquids are vast, and interlinked with vital everyday processes: new ionic solvents can be easily tailored to address the needs of a specific chemical reaction across a wide range of applications.
To understand the economic importance of ionic liquids – also known as ‘ionic salts’ – and liquid electrolytes, we must consider their properties. As the name suggests, ionic liquids contain clusters of ions (or electrically charged atoms), characteristically associated with salts. Ionic liquids, just like the powdered sodium chloride you sprinkle on your food, are salts. But distinguishing theses fine salts from your standard everyday table salt couldn’t be any easier: while table salt has to be heated to over 800 degrees Celsius to become a liquid, the anti-biofilm agents in ionic liquids remain fluid at the ambient room temperatures found in hospitals. Thankfully, therefore, there’s no chance of you accidentally grabbing a bottle of ionic liquid next time you’re in the chipper.
The ionic salts consist of an organic ‘cation’ (or positively charged ion), typically an ammonium or phosphonium salt, and an inorganic ‘anion’ (or negatively charged ion). The beauty of such salts is that anions and cations can be fine-tuned to offer a wide range of solvent properties, which in turn can be manipulated and utilised to their full chemical or medicinal advantage. Ultimately, ionic liquids possess properties similar to many other polar solvents with high boiling points.
Many types of bacteria (such as the hospital superbug MRSA, which is resistant to antibiotics) exist in colonies that reside on the surfaces of materials. Such colonies are typically cloaked in coatings, known as biofilms, which protect them from antiseptics, disinfectants, and antibiotics. These microbial biofilms have not only blanketed our hospitals in recent years, but have also been seen to lodge and thrive inside water pipes and cause pipe blockages in industrial processes. The aim of the game in tackling this bug therefore, from a medicinal point of view, is to concoct a medicinal mixture that strike a balances between having the lowest possible toxicity to humans, while being potent enough to erradicate the colonies of bacteria that live on our skin.
Luckily for us, the shield of resistance built by these biofilms has been breached, thanks to ionic liquids – and what’s more, it’s Ireland that has left the rest of the planet green with envy, as we emerge as one of the world leaders in mastering the chemical application of ionic liquids. The Queen’s University Ionic Liquid Laboratories (or ‘QUILL’) in Belfast, considered to be one of our island’s hidden gems in the field of green chemistry, is the world’s first specialist facility in the research of iolic liquids. Experts at QUILL have recently developed new agents to combat MRSA in the form of ionic liquid which attacks the infection in two ways – by killing colonies of these lethal microbes, and by disabling the ability to produce the biofilms that provide shelter for such bacteria. “We have shown that when pitted against the ionic liquids we developed and tested, biofilms offer little or no protection to MRSA, or to seven other infectious microorganisms,” reports Martyn Earle, QUILL’s assistant director.
There are a multitude of applications for an ionic liquid-based antiobiofilm – mostly, such as the aforementioned effects on MRSA, in the medical arena, where they can be used to improve infection control and reduce patient morbidity in hospitals, thus alleviating some of the financial burden to healthcare providers. But another project QUILL and other institutes have initiated deals with the application of ionic liquids for the removal of chewing gum on our streets. After all, if ionic liquids can dissolve rock and plastic, dissolving chewing gum is a bite-sized problem that ionic liquids can most certainly resolve.
Who knows, the substance may be just that elixir of life needed to boost our globe’s immune system against the symptoms of global warming, or Earth’s other imminent dangers. There’s no limit to what ionic liquids can do – it seems that we, unlike the ancient Greeks, are smart enough to acknowledge that, as once coyly noted in Mean Girls, the limit does not exist.