The growing Hospital Acquired Infections as well as Covid infections transmitted from contaminated solid surfaces over the past few years have challenged our ability to fight harmful microorganisms effectively. Cationic surfactants (quaternary nitrogen compound or abbreviated as quats) are one of the most widely used disinfectants. Despite their intensive use, little is actually known about how cationic surfactants interact with microbial membranes and kill the pathogens in the presence of other additives, e.g. hard water ions, nonionic surfactants. This situation limits our ability to design and formulate effective disinfectants. Weak or ineffective disinfectants, when used in hard surface cleaning (surgical devices, beds and airing systems and even food and diary processing facilities), could lead to outbreaks that could cost millions and, in some cases, have casualties. A formulated cationic quat disinfectant cleaning product often contains nonionic surfactants to provide cleaning efficacy. Despite decades of research and development, little is known about the role of the nonionics in disinfection. This lack of understanding creates a vacuum when new products are developed. Without this vital information about the interfacial biocidal action of such blends it is difficult to balance the levels of quats in product formulation. Biocidal quat molecules can bind (and usually do) to microbial membranes via strong electrostatic attraction and kill pathogens by structural disruption and membrane leakage. This mode of action is well supported by the rugged or disrupted surfaces of bacteria and fungi viewed from imaging studies such as scanning electron microscopy and confocal microscopy. Membrane disruptions have also been monitored by membrane permeation probes and fluorescence detection, zeta potential measurements and dynamic light scattering using lipid membrane models, such as spread lipid monolayer, supported lipid bilayer and small unilamellar vesicles (SUVs). High consistency to real microbial measurements validates the model membrane approaches. However, current techniques do not have the sensitivity or resolution to structural changes within the membrane which is typically in the region 1-5 nm. Lack of capability to follow structural changes during a biocide binding makes it difficult to distinguish one biocide from another or explore the impacts of different membranes. Neutron reflection (NR) and scattering (SANS) are about the only techniques that offer the insights into the structural changes across lipid membranes upon quat binding, with and without nonionic surfactant. Successful demonstration of the neutron experiments in this exploratory project replies on (a) input of neutron expertise in the running of the neutron experiments, synthesis of the deuterated surfactants and data analysis and interpretation from the ISIS team, (b) the expertise of antimicrobial work and selection of model lipid membranes from the Manchester team and (c) the active participation of Arxada in relating model interfacial studies to real quat formulations. The project teams have worked together to devise the challenging workplan that will be delivered by a highly able PDRA, Dr Mingrui Liao, who has already had prior knowledge of the quat biocides in his current PDRA work and neutron experiments from his PhD research on antimicrobial peptides. Successful outcomes from this project will form a strong basis for the collaborating teams to send joint grant applications to BBSRC and EU to engage in this new area of research by seeking more systematic neutron experiments. The teams will also publish their results in leading international journals such as JACS and Nat Commun.

Aerosol science, the study of airborne particles from the nanometre to the millimetre scale, has been increasingly in the public consciousness in recent years, particularly due to the role played by aerosols in the transmission of COVID-19. Vaccines and medications for treating lung and systemic diseases can be delivered by aerosol inhalation, and aerosols are widely used in agricultural and consumer products. Aerosols are a key mediator of poor air quality and respiratory and cardiac health outcomes. Improving human health depends on insights from aerosol science on emission sources and transport, supported by standardised metrology. Similar challenges exist for understanding climate, with aerosol radiative forcing remaining uncertain. Furthermore, aerosol routes to the engineering and manufacture of new materials can provide greener, more sustainable alternatives to conventional approaches and offer routes to new high-performance materials that can sequester carbon dioxide. The physical science underpinning the diverse areas in which aerosols play a role is rarely taught at undergraduate level and the training of postgraduate research students (PGRs) has been fragmentary. This is a consequence of the challenges of fostering the intellectual agility demanded of a multidisciplinary subject in the context of any single academic discipline. To begin to address these challenges, we established the EPSRC Centre for Doctoral Training in Aerosol Science in 2019 (CDT2019). CDT2019 has trained 92 PGRs with 40% undertaking industry co-funded research projects, leveraged £7.9M from partners and universities based on an EPSRC investment of £6.9M, and broadened access to our unique training environment to over 400 partner employees and aligned students. CDT2019 revealed strong industrial and governmental demand for researchers in aerosol science. Our vision for CDT2024 is to deliver a CDT that 'meets user needs' and expands the reach and impact of our training and research in the cross-cutting EPSRC theme of Physical and Mathematical Sciences, specifically in areas where aerosol science is key. The Centre brings together an academic team from the Universities of Bristol (the hub), Bath, Birmingham, Cambridge, Hertfordshire, Manchester, Surrey and Imperial College London spanning science, engineering, medical, and health faculties. We will assemble a multidisciplinary team of supervisors with expertise in chemistry, physics, chemical and mechanical engineering, life and medical sciences, and environmental sciences, providing the broad perspective necessary to equip PGRs to address the challenges in aerosol science that fall at the boundaries between these disciplines. To meet user needs, we will devise and adopt an innovative Open CDT model. We will build on our collaboration of institutions and 80 industrial, public and third sector partners, working with affiliated academics and learned societies to widen global access to our training and catalyse transformative research, establishing the CDT as the leading global centre for excellence in aerosol science. Broadly, we will: (1) Train over 90 PGRs in the physical science of aerosols equipping 5 cohorts of graduates with the professional agility to tackle the technical challenges our partners are addressing; (2) Provide opportunities for Continuing Professional Development for partner employees, including a PhD by work-based, part-time study; (3) Deliver research for end-users through partner-funded PhDs with collaborating academics, accelerating knowledge exchange through PGR placements in partner workplaces; (4) Support the growth of an international network of partners working in aerosol science through focus meetings, conferences and training. Partners and academics will work together to deliver training to our cohorts, including in the areas of responsible innovation, entrepreneurship, policy, regulation, environmental sustainability and equality, diversity and inclusion.