An academic and industrial partnership has investigated the antimicrobial activity of two types of disinfectant, finding they are more effective when used together.
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.
Effective disinfection 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.
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; and 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.
The team found that C12E6 binds to the outer membrane and partially inserts into the inner membrane of Gram-negative Escherichia 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.
Professor Jian Lu, lead author of the paper, commented: “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.”
- Liao M, Shen K, Ma K, et al. Unveiling the multifaceted mechanisms of action in nonionic and cationic biocide combinations against Gram-negative bacteria. J Colloid Interface Sci. 2025;696:137891. doi:10.1016/j.jcis.2025.137891