A team led by researchers from The University of Manchester used a range of techniques to study the interactions between a typical disinfectant and microbial membranes.
This was carried out in collaboration with industrial partner Arxada and scientists from the Science and Technology Facilities Council’s (STFC) ISIS Neutron and Muon Source.
The collaboration was funded through a Biotechnology and Biological Sciences Research Council (BBSRC) Prosperity Partnership award.
Why understanding disinfectants matters
Disinfectants are a key tool for fighting disease and infection.
Effective disinfection of public facilities reduces the cross-contamination of transferable diseases, cutting down the need for hospitalisation and antibiotic treatment.
However, despite their widespread and critical use, there is little understanding of how they actually work.
Investigating two disinfectant surfactants
In their study, published in the Journal of Colloid and Interface Science, the researchers investigated the antimicrobial mechanisms of two representative disinfectant surfactants:
- cationic didecyldimethyl ammonium chloride (DDAC)
- non-ionic hexaethylene glycol monododecyl ether (C12E6)
They examined the antimicrobial activity of each surfactant, both individually and in combination, against Gram-negative bacteria.
To gain further insight into the mechanisms behind this activity, the team studied the surfactants’ interactions with model lipid bilayers using multiple techniques, including:
- small-angle neutron scattering on Zoom at the ISIS Neutron and Muon Source
- neutron reflectivity (NR) on Inter and OffSpec at the ISIS Neutron and Muon Source
- NR at the Institut Laue-Langevin
The researchers used a range of selective deuteration methods to build a detailed picture of how the two surfactants interact with both the inner and outer bacterial membranes.
The researchers worked closely with the ISIS Neutron and Muon Source deuteration laboratory to complete this work.
What the research found
The team found that C12E6 binds to the outer membrane and partially inserts into the inner membrane of Gram-negative E. coli, causing mild destabilisation but no significant membrane disruption.
In contrast, DDAC strongly binds to and inserts into both outer and inner membranes, leading to effective membrane leakage and cell damage, which is the effect needed from a disinfectant.
When the two surfactants are combined, C12E6 facilitates DDAC insertion, enhancing membrane disruption.
However, an excess of C12E6 decelerates the bacteria-killing power of DDAC.
New products to fight antimicrobial resistance
Professor Jian Lu, lead author of the paper, said:
The different molecular interactions revealed by the neutron experiments and biophysical assays help us to understand the roles of different surfactants in a formulated product, by linking their membrane disruptive behaviour with their antimicrobial efficacy.
This paves the way forward for new product formulations in our fight against antimicrobial resistance.
Critical funding
Dr Jordan Petkov, Director Strategic Projects and External Research at Arxada, said:
The BBSRC STFC Facility Access Fund has been absolutely critical in allowing us to move quickly and with confidence in this area of research.
For a company like Arxada, the ability to access state-of-the-art facilities such as STFC ISIS neutron and muon source and collaborate with world-leading project scientists has provided invaluable insights into how our biocides function at the most fundamental level.
These grants not only enabled us to validate our hypotheses and demonstrate feasibility, but were also instrumental in securing the Prosperity Partnership.
We are excited to continue this collaboration with The University of Manchester and UK Research and Innovation facilities, tackling one of the most urgent scientific and societal challenges of our time.