Tanumita Misra

Effect of a higher concentration of ethanol (40% (a) and 70% (b)) is shown on multiple biomimetic vesicles at different times (in nanosecond, ns) after the addition of ethanol molecules in the system. Only lipid molecules are shown for clarity.

The world witnessed a surge in demand for the hand sanitizers amidst the COVID-19 outbreak, as the transmission of viral infections is known to be inhibited by the usage of appropriate alcohol-based hand sanitizer. These sanitizers contain Ethanol, or ethyl alcohol that kills the pathogens like bacteria and viruses by rupturing the outer layers of their membranes.

While scientists worldwide have been making efforts to develop and beef up effective pharmaceutical interventions to fight against the pandemic, researchers at IIT Delhi have conducted a study to gain insight into the effect of ethanol concentration on biological membranes. They developed a new coarse-grained (CG) model to demonstrate the effect of alcohol on membranes enveloping the pathogens. As the study confirms the optimised ethanol concentration in sanitizers, the researchers anticipate that the developed model will helpexamine ethanol’s effect on more complex and realistic membrane systems like plasma and bacterialmembranes.

The plasma membrane, or the cell membrane, is a semi-permeable membrane enveloping the cell’s cytoplasm. The membrane provides structural integrity to the cell by controlling the movement of substances within and outside the cell. Ethanol, or alcohol, is known as a pharmaceutically active molecule owing to its ability to disrupt the structural integrity of lipid bilayer by modulating its properties. A lipid bilayer is a biological membrane having two layers of lipid molecules that are the principal components of the cell membrane. The outer coatingof bacteria and viruses is made of protein and lipids. Ethanol, used in hand sanitizers, kills the bacterium or virus by targeting and damaging this outer coating. 

Scientists are keen on investigating the mechanism under which ethanol destroys the outer membrane of viruses. This provides an understanding of the minimum concentration and the optimum time needed for ethanol to destroy the protecting layer membrane of viruses. The current study is novel in the fact that it employs the new CG model to examine the effect of changing ethanol concentration on the structure and stability of single and multiple biomimetic vesicles of lipids. Vesicles are tiny fluid-filled sacs that transport material inside and outside the cell. “Unlike the previous theoretical studies that have focused mostly on a single and flat (planer) membrane bilayers, here, for the first time, we have looked at the effect of ethanol on multiple membrane vesicles,” says Dr. Hemant K. Kashyap, corresponding author of the study recently published by the Langmuir. Dr. Kashyap is Associate Professor in the Department of Chemistry, Indian Institute of Technology Delhi.

“We have shown that up to 20% of ethanol hardly affects the overall integrity of lipid vesicles, except their swelling. However, the ethanol molecules have enhanced detrimental effects beyond this concentration,” he adds. The authors of the study have demonstrated that at 70% ethanol concentration which is recommended amount of alcohol in hand sanitizers, the vesicle membranes disruption is far greater than what is observed at 40% ethanol.

The overarching findings reveal that from low to moderate concentrations, ethanol causes swelling and aggregation in multiple vesicles, whereas its higher concentration results in rupture of both single and multiple vesicles, the extent of which increases with increasing ethanol concentration.

“Our study’s results and observations directly provide us the molecular insight into the effect of hand sanitizers (containing ~>70% ethanol) on apathogenic membrane.This is otherwise impossible with the atomistic simulations, the tool used to predict lipid membranes’ physical and structural properties at the atomic level,” says Dr. Kashyap.

Ms Tanumita Misra is pursuing Masters in MSc (S&T Communication) from CSIR-NIScPR