Stefan Stolte

Mass-spectrometry-based proteomics is rapidly advancing, becoming fast, affordable, and increasingly accessible to environmental scientists. This perspective outlines how proteomics can illuminate biotransformation processes and sublethal organism-level effects, and highlights future opportunities enabled by emerging technologies. Our goal is to give a concise overview on realistic expectations of current capabilities while inspiring scientists to adapt and develop novel proteomic approaches addressing fundamental questions in contaminant science.

Polyhedral oligomeric silsesquioxanes (POSS) and ionic liquids (ILs) have emerged as highly promising components for the design of advanced hybrid materials. The integration of ILs onto the POSS core has led to the development of a novel class of materials known as POSS-based ILs (POSS-ILs), which synergistically combine the thermal and mechanical stability of POSS with the tunable physicochemical properties of ILs. Despite their great potential, a detailed and unified review covering the synthesis, properties, and multifunctional applications of POSS-ILs remains limited. This review therefore presents a thorough discussion of their synthetic approaches such as direct functionalization, IL grafting, and sol-gel techniques alongside their distinctive physicochemical features, including high thermal and mechanical stability, ionic conductivity, viscosity control, tunability, solubility, and chemical resistance. Furthermore, the roles of POSS-ILs in catalysis, energy storage and conversion, smart materials, analytical applications, and wastewater treatment are systematically explored. The review also highlights current challenges related to structure-property relationships and multifunctionality, while outlining future perspectives for optimizing POSS-ILs as sustainable, high-performance materials. Overall, this review aims to serve as a comprehensive resource for researchers across materials science, nanotechnology, and environmental chemistry, supporting the continued innovation and application of POSS-ILs in next-generation functional systems.

High environmental concentrations of pharmaceuticals, particularly antibiotics, have been observed worldwide, while antibiotic concentrations in the ng/L to µg/L range may adversely affect biota and contribute to the formation of antibiotic resistance. The underlying causes of high environmental concentrations include, in addition to the low rate of antibiotic’ metabolization and the high rate of usage, especially of β-lactam antibiotics, the insufficient removal by conventional wastewater treatment methods. Consequently, alternative methods need to be developed to remove antibiotics from wastewater—one possibility is the use of enzymes. In this study, the enzyme β-lactamase was secreted by a genetically modified yeast ( Saccharomyces cerevisiae ) upon recognition of a pheromone (α-factor) as inducer to enable the degradation of ampicillin. This represents a crucial step on the road to a sensor-actuator system, allowing for the development of an intelligent removal system that can react to the presence of antibiotics. Ampicillin and its transformation products were studied by LC–MS/MS measurements using a carbamoyl functionalized column under hydrophilic interaction liquid chromatography (HILIC) conditions, which allowed detection of ampicillin at concentrations of 2.43 nM. The dependence of ampicillin degradation on α-factor concentration and the cultivation time of the yeast was demonstrated, resulting in higher degradation rate with higher α-factor concentrations and longer yeast cultivation times. Over 90% of 10 µM ampicillin was degraded within 0.5 h using 250 nM α-factor and a cultivation period of 24 h. Finally, the transferability to other β-lactam antibiotics was investigated, resulting in complete degradation of amoxicillin, penicillin G and piperacillin within 24 h.

Testing the bioaccumulation and chronic toxicity of (highly) hydrophobic compounds is extremely challenging, but crucial for hazard assessment. Fish are used as a model organism in these tests, but have many limitations, including a long time to reach steady-state, difficulty in maintaining constant exposure, and ethical concerns. We developed a method for the (simultaneous) assessment of chronic reproductive toxicity and bioaccumulation using Daphnia magna as a model organism. As test chemicals, we selected heterocyclic polyaromatic hydrocarbons (heterocyclic PAHs), which are often persistent and show high acute aquatic toxicity, raising concerns about their long-term effects. In this study, we developed a robust passive dosing method to maintain constant exposure in chronic toxicity and bioaccumulation tests of four heterocyclic PAHs in Daphnia magna. Passive dosing maintained stable exposure concentrations in the ng to μg L^-1 range, even after reusing disks up to three times. All chemicals were toxic to Daphnia magna with EC₁₀ values between 0.1 and 15 μg L^-1. Bioaccumulation tests showed that steady-state was not reached, and the uptake rate constant (k₁) could not be reliably determined due to complex exposure routes (both via water and diet). However, depuration rates in Daphnia magna were about 2 orders of magnitude higher than in fish, which is advantageous in the assessment of highly hydrophobic compounds. We propose to use the depuration rate constant (k₂), which is independent of the uptake route, as an indicator of bioaccumulation potential. The k₂ thresholds for Daphnia magna were estimated to identify (very) bioaccumulative compounds by correlating k₂ values with bioconcentration factors (BCFs) for Daphnia magna and applying fish BCF thresholds. We suggest that a Daphnia magna bioaccumulation test can be used as a screening tool to trigger further bioaccumulation testing in fish, as it offers higher throughput, is more ethical, and reaches steady-state faster. However, further validation with reference test protocols and substances is essential.

High-throughput cell-based bioassays can fulfill the growing need to assess the hazards and modes of toxic action (MOA) of ionic liquids (ILs). Although nominal concentrations (C_nom) are typically used in an in vitro bioassay, freely dissolved concentrations (C_free) are considered a more accurate dose metric because they account for chemical partitioning processes and are informative about MOA. We determined the C_free of IL cations in AREc32 and AhR-CALUX assays using both mass balance model (MBM) prediction and experimental quantification. Partition coefficients between membrane lipid-water (K_mw), serum albumin-water (K_albumin/w), and cell-water (K_cell/w) as well as potential confounding factors (binding to a test plate and micelle formation) were determined to improve the MBM prediction. IL cations showed a higher affinity for both cell lines than that predicted by the MBM based on K_mw and K_albumin/w. Their affinity for the AhR-CALUX cells was more than 1 order of magnitude higher than for the AREc32, signifying cell line-specific affinity. The MBM with an experimental K_cell/w accurately predicted C_free. Evaluating cytotoxicity based on C_free eliminated the leveling off of toxicity observed for hydrophobic IL cations (side chain cutoff), suggesting that C_nom underestimates the effects of compounds with high affinity for the assay medium. Cell membrane concentrations calculated from C_free using K_mw were compared to the critical membrane burden to identify whether IL cations act as baseline toxicants. The IL cations carrying 16 carbons in the chain in the AREc32 assay and most of the IL cations in the AhR-CALUX assay were classified as excess toxicants. However, since the reasons for the deviation of experimental K_cell/w from MBM prediction remain unexplained, it is uncertain whether the cell membrane concentrations can be well predicted from K_mw used in this study. Therefore, future studies should aim to uncover the underlying causes of differing cell affinities observed across cell lines and model predictions.

Bacteria and yeast use secreted signal peptides, also known as pheromones, for cell–cell communication within their respective species. Recently, genetic modification has allowed for the extension and exploitation of this type of communication, to communication between organisms from different species and even from different kingdoms. This innovative approach is intended to allow for the large-scale production of specific compounds for applications in medicine and biotechnology while producing reduced amounts of by-products. Until now, the detection of signal peptides, which are often short-lived and only present in small amounts, is usually qualitative, non-selective, and time-consuming and/or requires the presence of additional cell types. Here, an ESI-LC–MS/MS method for the specific quantification of signal peptides from yeast (α- and P-factor) and bacteria (CSF) using a TSKgel column operating under HILIC conditions has been demonstrated. The influence of different matrices, their adsorption behavior, and their stability were investigated. In matrix, LOQs of 0.05 µM, 0.03 µM, and 0.02 µM were obtained for CSF, α-factor, and P-factor, respectively. Subsequently, the developed method was applied to the detection of yeast- and bacteria-specific peptides secreted by genetically modified yeasts. It could be demonstrated that under overexpressing conditions, α-factor and P-factor concentrations of 1 µM were measured, while for CSF concentrations as high as 2.5 µM was reached. Finally, the established method permits the simultaneous, quantitative detection of signal peptides in different matrices and without pre-concentration in near-real time, thus advancing the possibility of tracking cross-kingdom communication. Graphical Abstract

The recovery of valuable materials from spent lithium-ion batteries (LIBs) has experienced increasing demand in recent years. Current recycling technologies are typically energy-intensive and are often plagued by high operation costs, low processing efficiency, and environmental pollution concerns. In this study, an efficient and environmentally friendly dielectrophoresis (DEP)-based approach is proposed to separate the main components of "black mass" mixtures from LIBs, specifically lithium iron phosphate (LFP) and graphite, based on their polarizability differences. A custom-designed microparticle separator is developed for the continuous separation of LFP and graphite mixtures at high throughput. Additionally, a theoretical model incorporating both electric and flow fields is constructed to predict the DEP behavior of particle streams. The feasibility of selective separation is theoretically evaluated through numerical simulation of microparticle trajectories and binary separation within the proposed separator, and these results are experimentally validated with good agreement. Under a particle streamflow rate of 10.8 mL/min, both simulations and experiments demonstrate a separation efficiency of LFP higher than 80% at 100 V. Furthermore, the influence of operating parameters, such as the applied voltage, flow rate, and sheath-to-feed ratio, on optimal separation efficiency and particle purity is numerically investigated. The feasibility of the proposed separator for the potential separation of other lithium-metal-oxide-containing particle mixtures is also explored through numerical simulations. Overall, this study provides a theoretical foundation for the development of high-performance and sustainable LIB recovery processes with a low energy consumption.

Innovative thermal battery technology has the capability to revolutionize the renewable energy storage market. Its cost-effectiveness, scalability, contribution to CO₂ reduction, and lack of reliance on rare earth metals set it apart. Nevertheless, the overall efficiency and sustainability of this technology hinge on crucial factors such as the sources, performance, and cost of the associated phase-change material (PCM). Fatty acid esters with biorenewable origins meet the sustainability criteria yet are limited to low-temperature applications (mostly −1, improved melting temperatures up to 94 °C, and high stability demonstrated over more than 500 cycles. With the aid of Fourier-transform infrared spectroscopy (FTIR), synchrotron single-crystal X-ray diffraction, and Hirshfeld surface analyses, we obtained insights into the molecular interactions dictating the extraordinary thermal properties of sugar acid-derived esters, which could be feasible as PCMs for sustainable and inexpensive energy storage.