Lecture program

In recent years, polyelectrolytes have attracted attention due to their potential low fouling properties and specific interactions with biological matter and cells. Amino acids as natural zwitterionic molecules may serve as starting material for the preparation of amino-acid-derived polyelectrolytes, which, in addition to their charge, also carry other biomimetic motifs such as chirality.

We describe the potential to exploit amino acids for the preparation of polyelectrolytes via different synthetic approaches and their characterisation. We further show how minor changes to the chemical Identity of amino-acid-derived polyelectrolytes can lead to drastic changes in their properties as well as their interactions with biological matter. This presentation aims to show the potential of amino acid derivates for the preparation of systematic polymer libraries, which are well needed to gain a better understanding about structure-property-relationships of polymer systems.

Properties of surfactant formulations are regularly modified by cosurfactant addition, resulting in systematic control of structure and properties. The structural changes are supposed to proceed by changing continuously the packing parameter of the self-assembled aggregates. Accordingly, cosurfactant addition to spherical micelles transforms them into increasingly longer wormlike micelles and at still higher cosurfactant concentration to bilayers by proceeding through a first order phase transition.
In this work we show a substantially different self-assembly behaviour, seen for a classical nonionic surfactant (Tween 20) upon addition of 2-ethylhexylglycerol (EHG) as cosurfactant. Structural characterisation by light and neutron scattering (SLS, DLS, SANS), and especially cryo-TEM, shows that here elongated assemblies are formed. However, in contrast to normal expectation, they are composed of individual micelles that are locally ordered in a cylindrical fashion, which also explains the much lower viscosity observed in comparison to normally expected worm-like micelles (WLM). A first-order phase transition takes place at higher cosurfactant content, but here only a smaller fraction of amphiphile initially forms a bilayer structure and complete transformation to bilayers occurs within the single-phase region for EHG concentrations much higher than the ones of the phase transition.
This very uncommon structural evolution has not been reported before, but can be rationalised by the particular structure of the amphiphilic molecules involved. This work was then extended to other nonionic surfactants and cosurfactants with systematic variation of the head group size. As a result, the systematic variation of the phase behaviour can be assigned to the molecular architecture of the amphiphiles.

Multifunctional ingredients (multifunctionals) are gaining increasing attention in the cosmetics, personal care and home care industries. These are ingredients that can provide more than one functional characteristic in a formulation. Furthermore, the introduction of such ingredients early in the formulation process provides an opportunity to substitute or use other functional ingredients more efficiently as a result of synergetic effects, thus enabling the creation of more environmentally friendly and gentle products. Examples of multifunctionals, which will be presented, include poorly water-soluble amphiphilic fragrances and preservatives, such as geraniol, linalool, phenoxyethanol, which are able to lower the surface tension of aqueous solutions.
The studied amphiphilic substances, in addition to creating a certain scent, also demonstrate a high dynamic surface activity and affect the process of micelle formation of surfactants, as well as the rheological and release properties of emulsions. The introduction of these substances into the system at the early stages of the production process will improve the processes of emulsification, dispersion, solubilisation.
Another example of a multifunctional is given by an anionic polyelectrolyte – fully neutralized polyacrylic acid (PAA), which has a primary function as a binder in detergent formulations. Association behavior in a complex multicomponent system, containing ethoxylated anionic surfactants, PAA and enzymes, which possess a high efficiency to solubilize poorly water-soluble immobilized proteins is analyzed using a set of methods, including dynamic tensiometry and solubilisation assay. Unexpected attractive interactions of PAA with like-charged surfactants in the presence of multivalent cations are confirmed. Revealed novel electrostatic association mechanisms may give rise to new design approaches towards sustainable detergency.

Earth resources are limited and so is the ability for humanity to grow on Earth. The impact of detergent chemistry goes beyond green chemistry but the holistic impact on Earths resources is rarely understood. To guide future research towards a holistic detergent design, Urner lab leverages the planetary boundary framework to assess systematically the impact of detergent chemistry on the transgression of Earth’s resources. Our results show that the implementation of a climate-friendly detergent industry is making progress. Improvements are needed in aligning materialistic and societal aspects in creating technical solutions by means of sustainable chemistry, also from the perspective of academic family trees. Furthermore, we show that the development of detergents that serve the purposes of applications but do not harm the wider biosphere remains to be explored. We propose an important key parameter to be considered in future research is the membranolytic property, which describes the dissolution of cell membranes by detergent. Cell membranes are the first point of contact with detergents and related membrane damages are linked to cell stress, inflammation, allergy, antimicrobial resistance and maybe even cancer development. To support new directions in developing safe-to-use detergents, we expanded the detergentome by modular hybrid detergents to provide new possibilities in structure-activity studies. Methodological capabilities provided by our modular hybrid detergent chemistry unlock full flexibility in tuning molecular parameters that determine applications and membrane interactions, including charge, polarity, and molecular shape. Taken together, we present a new detergent class and demonstrate utility of the planetary boundary framework for guiding future research towards sustainability, regardless of the chemistry. Our results also imply that safe operating spaces that humanity needs for its survival may be secured by directing additional future efforts in detergent chemistry beyond sustainable chemistry, resource efficiency, and net zero emission targets.

The complexation induced by cationic polyelectrolyte (cPE) is considered to be an effective method in conventional water treatment process to deal with negatively charged humic acid (HA), which exists ubiquitously in aquatic environments and negatively affects the quality of drinking water. Accordingly, in order to optimize this process in a rational way, it is essential to understand the interaction between HA and cPE in fundamental physico-chemical terms.

In this study, a series of modified cationic (quaternized) chitosan (qCs) that derived from natural waste are utilized as cPE to develop an environmentally friendly solution. The colloidal structure of the formed HA-qCs complexes are probed by synchrotron-based small-angle X-ray scattering (SAXS) as a function of mixing ratio and pH. In addition, by combining with stopped-flow devices, the kinetics of early-stage complex formation in a timescale of ms can be probed. It was observed that by tailoring the degree of quaternization of qCs, a shift of the phase diagram revealed which correlates with the aggregate structure, which in turn affects their larger scale organization and propensity for flocculation. This insight from colloid science is promising to optimize the water treatment process in industrial fields.

In 2022, the standard EN 17658 for laundry disinfection was released which uses Candida albicans as a test organism for yeasts.

Recently, a rise in infections by different Candida species, such as C. auris and C. parapsilosis, have been reported [1–3], which could result in a higher relevance of these species for laundry hygiene, not only in the hospital, but also in domestic health-care settings.

This study focuses on the reduction of different Candida strains in standardized laundry processes according to EN 17658 to detect possible differences between the original test strain and emerging pathogenic Candida species.

A commercially available powder colour detergent, colour detergent combined with addition of a bleach releasing additive and a heavy-duty detergent were compared to the IEC A standard detergent with and without added activated oxygen bleach. Test were performed at temperatures from 20°C to 40 °C, covering the temperature range of the test method.

The experimental setup allows for an assessment of the hygiene efficacy based on domestic washing procedures, which are important for people being cared for at home.

Our results show a differential behavior of the investigated strains, thus suggesting a need for monitoring the hygienic efficacy of laundry processes on emerging Candida species.

References:
Branco, J., Miranda, I. M. & Rodrigues, A. G. Candida parapsilosis Virulence and Antifungal Resistance Mechanisms: A Comprehensive Review of Key Determinants. J. Fungi 9, 80 (2023).
Sun, M. et al. Increase in Candida parapsilosis candidemia in cancer patients. Mediterr. J. Hematol. Infect. Dis. 11, 1–7 (2019).
Cristina, M. L. et al. An Overview on Candida auris in Healthcare Settings. J. Fungi 9, 913 (2023).

Powerful detergents and cleaning agents require ingredients with specific functional properties in complex formulations. The production of these ingredients takes place within value chains involving numerous stakeholders and integrated facilities. Sustainable development of detergents, particularly the reduction of greenhouse gas emissions, therefore, requires the collaboration of companies along the value chain. Key factors for this lie in the increasing use of circular raw materials from sustainable biomass, recycling, and carbon capture and utilization (CCU) sources, the transition of energy supply in production towards renewable energies, the establishment of new and more efficient processes for greenhouse gas reduction in production, as well as the development of ingredients and formulations that enable energy savings during consumer use. The further development of standards for calculating and exchanging company-specific, comparable product carbon footprints leads to increased transparency of emission sources along the value chain, enabling the sustainable management of raw material portfolios and development candidates in the future. The challenge lies in the development of capacities through economically and technically feasible greenhouse gas reduction measures towards net-zero emissions within the next maximum 25 years, which can only be achieved gradually. Through the use of mass balance, already implemented partial transitions at the company level can nevertheless be immediately and fully attributed to selected ingredients and customers within the value chain, making their effect visible and beneficial. Current developments will be presented using examples.

It is possible to lower the carbon footprint of e.g. a laundry detergent by replacing part of the petrochemically-derived surfactants by a biosurfactant, which is not only fully biobased, but also made biologically. Is this, however, already green washing (or just greenwashing)? Starting from the fact that Rhamnolipids are produced by enzymes, it should not come as a surprise that biosurfactants are inherently compatible with proteins. Likewise, the lack of interaction with cationic groups of a protein is also the reason why the deposition of cationic polymers on hair is greatly improved, in case the classical anionic surfactants in a conditioning shampoo was completely replaced by Rhamnolipids. Likewise, in laundry detergents, substituting only a small portion of the classical surfactants by biosurfactants is hardly sufficient to utilize their full potential: Green washing requires new formulation concepts, based on the special properties of biosurfactants. In addition, biosurfactants must have some compatibility with microorganisms, at least with their producers, while inhibiting others. This is an important aspect, since it is commonly expected by consumers that washing hands using soap helps to fight microbes. A selective antimicrobial action might thus help to reduce harmful germs while protecting the natural skin microbiota.

We leave our marks on everything we touch. They are on the lenses of our glasses, on the keyboards we are working with, or on the door handles of our homes. Despite such omnipresent transfer of skin lipids, their removal is more complex. Cleaning materials are insufficiently wettable with lipids and additional detergents are urgently needed. Nevertheless, the development of specialized cleaning tools is possible and can be facilitated by dedicated surface characterizations applying contact angle measurements. As this approach is strongly dependent on the kind of soiling, the presented study concentrates on lipid-containing artificial skin and serves as exemplary application. For this purpose, insights are obtained by application of the Zisman model. As it describes the surface energy a liquid needs to spread completely on a solid, a comparison with the surface energy of the soiling is advisable. However, as not only the surface energy itself is of importance but the magnitudes of the individual surface energy components and corresponding molecular interactions are too, the Van Oss model is utilized. This differentiation between interactions gives important information about the underlying adhesion mechanism. If both models are combined, dedicated conclusions concerning an appropriate material are possible. Therefore, this application can potentially facilitate the development of specialized cleaning equipment.

We study volatile aroma substances (linalool, citronellol, geraniol, menthol) with respect to their ability to adsorb on air/ water (A/W) interfaces — they are highly surface active, and exhibit rather fast initial adsorption, as demonstrated by surface tension measurements. The equilibrium adsorption isotherms are also discussed, together with the relevant physico-chemical parameters. The „surfactant – like” properties of these perfume ingredients are influenced by evaporation. We carry out model experiments with gradual saturation of aqueous pendant drops from vapors, followed by subsequent evaporation into open air, and also do measurements with evaporation from drops of solutions. The A/W surface tension is found to increase vs. time, during evaporation. The data are interpreted according to simple model considerations which include the impact of barriers for desorption towards the gas phase [as described in Colloids Surfaces A 625 (2021) 126931, Langmuir 38 (2022) 2793]. An important kinetic parameter is determined — the mass transfer coefficient, quantifying the rate of molecular exchange through the interface. During the course of evaporation, the surface elasticity is also measured, by means of small oscillations in the area/ volume of the drop. The observed trend is a gradual increase of the elasticity moduli, which can be rationalised in the context of the contribution of local fluxes of mass transfer of the volatile amphiphile (perfume) between the interface and the adjacent sub-surface, when the area is expanded or contracted. Our results can be useful when explanations are sought for the role of aroma substances in stabilizing disperse systems (e.g., droplets), under dynamic conditions when mass exchange (evaporation) takes place simultaneously with adsorption/ desorption.

Acknowledgements
The authors wish to thank for financial support provided by the European Union – NextGenerationEU, through the „National Recovery and Resilience Plan” of the Republic of Bulgaria, contract # 70-123-260/2024, project BG-RRP-2.004-0008 SUMMIT.

Carbohydrates are true multitalents – they are an important energy source such as glucose, they are highly variable materials such as cellulose and they play a pivotal role in many biological information processes such as cell-cell communication. Thus, bringing together carbohydrates and synthetic polymers in the development of so-called glycopolymers leads to highly variable and diversely functional materials with broad applications. This talk will focus on the synthesis and applications of amphiphilic glycopolymers – their self-assembly and adhesion properties as well as their applications for pathogen detection and inhibition.