Ionic liquids (ILs) are compounds known for the low melting points. They have attracted recent attention from the scientific community due to their antimicrobial properties and effectiveness against many different types of pathogens including bacteria, fungi, and viruses.
In an age of increasing antibiotic resistance, alternative therapies are being looked at with high importance. With a high antimicrobial efficacy and customisable nature, ILs present a promising solution. It has previously been shown that they kill bacteria by interacting with the cell membrane, but the precise way in which they do this is not fully understood. In this study, published in The Journal of Physical Chemistry Letters, the team led by researchers from Bhabha Atomic Research Centre, Mumbai, used the technique of quasi-elastic neutron scattering at the IRIS beamline at ISIS to reveal the mechanism of action of imidazolium-based ILs.
IRIS enabled them to study the energy changes related to phase changes and to gain nanoscale insight into the dynamics of the membrane. The results showed that incorporation of ILs into a model bacterial membrane resulted in a noticeable change in membrane dynamics including structural rearrangement and an increase in membrane permeability which leads to bacterial death.
Their results further showed that an increased IL concentration led to faster lateral motion of lipid molecules and increased internal motions of the alkyl chains of lipid molecules. Additionally, they found a strong correlation between the alkyl chain length of ILs and their antimicrobial potency, providing insights for optimising IL-based antimicrobial agents.
Lateral and internal motions of lipids contribute to diffusion of lipids through the membrane bilayer and therefore impact its fluidity and permeability. Changes in lateral diffusion due to ILs can compromise the integrity of the membrane, which causes disruptions in the electrochemical gradient, osmotic imbalance and influx of toxic substances which leads to cell death.
The team’s neutron scattering experiments also revealed that longer chain ILs had a greater bactericidal effect due to their greater binding affinity, which means they disrupt the membrane more. By understanding how ILs interact with the membrane and how their structure impacts their function, they can be altered to precisely target various pathogens. This makes ILs a promising candidate for future healthcare applications.
