Improving the sustainability of cosmetic products while maintaining a good performance requires a deeper understanding on the way that new eco-respectful ingredients interact with hair or skin. In the case of shampoos, the surface science is dominated by the diverse changes on the hair fiber due to both chemical and physical damages that particularly affect physicochemical properties such as hydrophobicity. A native, undamaged fiber is covered with a monolayer of lipids, mainly 18-methyleicosanoic acid (18-MEA), while a highly damaged hair surface, having completely lost the protective lipids, is hydrophilic and negatively charged. Intermediate states exist, where there is a partial loss of 18-MEA (“partially damaged hair”). Here, four model surfaces have been produced, to mimic different types of hair surfaces. Their interaction with selected surfactants and polyelectrolytes (natural and synthetic) has been studied by neutron reflectometry (NR). NR can reveal hierarchical adsorption from mixtures thanks to the scattering contrast between deuterated and hydrogenous molecules. Atomic force microscopy (AFM) measurements complement the study by adding information about the in-plane structure of adsorbed species. The presence of the methyl branch of 18-MEA is found to affect the interaction of the surface with adsorbates. For surfactant/polyelectrolyte mixtures, for example, the adsorption of polymer is enhanced. Of particular interest are the results on the partially damaged hair model, as it manifests patches of hydrophobic and hydrophilic moieties; it is possible to separately observe the different adsorption behaviors to the different sites in a single experiment.

Nickel (Ni) is utilized in a wide range of applications, including the production of austenitic stainless steel, superalloys, rechargeable batteries, catalysts, and foundry products. Historically high exposure to mixed Ni dust has been associated with various health effects, including an increased risk of respiratory cancer. Different chemical forms of Ni exhibit distinct physicochemical properties and biological effects, and the role of these properties, including nanoparticles (NPs) vs microparticles (MPs), in the cellular uptake and fate is not completely understood. This study aims to explore the uptake, intracellular fate, and cytotoxicity of eight well-characterized Ni substances in BEAS-2B cells. Characterization was conducted using scanning electron microscopy, X-ray photoelectron spectroscopy, and dynamic light scattering. Uptake in BEAS-2B cells was investigated using transmission electron microscopy, Newport Green staining in combination with super-resolution microscopy, and atomic absorption spectroscopy. The characterization showed that the Ni substances differed in primary size but were all highly agglomerated under the conditions tested, with Ni3S2 having the largest size. At 48 h and based on the same mass of added Ni, Ni3S2 was the most cytotoxic, followed by the water-soluble salt NiSO4·6H2O and Ni metal NPs with a primary size of 80 nm (Ni80), while nickel oxide (NiO) NPs were noncytotoxic under the tested conditions. Biodissolution (released Ni per mass Ni added) in cell culture medium varied substantially across substances and generally increased with time. At 48 h, Ni biodissolution followed this order: Ni3S2 (55%) > Ni80 (9%) > NiO MPs (4%) > Ni 20 nm and NiO 80 nm (3%), > NiO 20 nm (2%) > Ni MPs (0.3%). All sparingly soluble Ni substances were clearly observable in intracellular membrane-bound structures in BEAS-2B cells. A key observation from the quantitative uptake was the distinctly lower uptake of Ni ions from the water-soluble NiSO4·6H2O compared to the sparingly soluble Ni substances. There was thus no clear correlation between apparent uptake and cytotoxicity. After fractionation into cytosolic, nuclear, and particulate fractions, followed by analysis of dissolved Ni from the particles within the cells, the three substances showing the highest amount of Ni per added Ni mass (indicating both uptake and intracellular Ni ion release) in both cytosol and nucleus were Ni20 NPs, Ni MPs, and Ni3S2. Super-resolution microscopy indicated increased Newport Green fluorescence, suggestive of intracellular Ni accumulation, predominantly in cells exposed to Ni MPs and Ni3S2. However, the findings were not sufficiently robust to allow firm conclusions. These findings highlight the complex interplay between biodissolution, cellular uptake and cytotoxicity of Ni substances.

Metal additive manufacturing (AM) relies on alloy feedstock powders that may come into contact with the workers’ skin during handling, yet skin-relevant data on metal release and biological reactivity remain limited. Here, we assessed the cutaneous bioactivity of the fine particle fraction of four gas-atomized Fe-based AM powders (316L stainless steel, Fe-powder A, and tooling steels B and C). Powders were sieved to <10 μm and characterized by scanning electron microscopy and X-ray photoelectron spectroscopy before and after incubation in artificial sweat (ASW). Metal biodissolution was quantified in ASW and keratinocyte culture medium using atomic absorption spectrophotometry. Cellular responses were evaluated in HaCaT keratinocytes using Cell Painting-based phenomics and multiplex cytokine/chemokine profiling and in an ex vivo full-thickness human skin explant model, including superficial barrier disruption, IL-8/CXCL8 quantification, and histological assessment. ASW exposure induced marked shifts in the outermost surface composition across powders, indicating sweat-driven surface transformation. Biodissolution was low and medium-dependent, with Fe dominating the release in ASW, and with an overall metal release remaining limited in cell culture medium. In HaCaT cells, MCP-1/CCL2, IL-6, and IL-8/CXCL8 were quantifiable but showed no significant changes following powder exposure. Cell Painting revealed subtle, shared phenotypic signatures, primarily involving mitochondrial-associated features, without evidence of broad cellular stress. In the ex vivo skin model, AM powders did not increase IL-8/CXCL8 secretion, the particles remained localized to the skin surface without detectable penetration, and coexposure with Staphylococcus epidermidis did not enhance bacterial colonization or induce inflammation. To the best of our knowledge, this is the first study that applies a human skin explant model to evaluate dermal responses to metal AM powders. Overall, the tested AM powders showed low short-term cutaneous reactivity under skin-relevant conditions, providing human-relevant evidence to inform occupational risk assessment in AM environments.

Austenitic stainless steel (AISI 316L) is the dominant material in food processing equipment due to high corrosion resistance and mechanical durability. The shift from animal-to plant-based food processing introduces new challenges for material performance, as plant-derived biomolecules may interact differently with food-contact surfaces than animal proteins. These interactions can modify interfacial properties, with consequences for fouling, corrosion, and metal migration. Despite its importance, such effects remain scarcely studied, with only a few reports on e.g. whey and casein proteins. Knowledge on rice-derived biomolecules is particularly limited, even though rice proteins and starches are increasingly relevant in gluten-free and plant-based systems. This study examines the adsorption kinetics and interfacial properties of rice protein concentrates (RPC) and rice starch (RS) dissolved in artificial tap water (ATW) onto 316L stainless steel. In situ quartz crystal microbalance with dissipation monitoring (QCM-D) was employed to quantify adsorption dynamics, complemented by atomic force microscopy (AFM) and carbohydrate-specific opto-tracing (Carbotrace 680) to detect, and visualize adsorption patterns. Atomic absorption spectroscopy (AAS) was used to determine metal migration and evaluated with respect to European Union specific release limits (SRLs) for food-contact materials. Electrochemical measurements including open circuit potential (OCP), potentiodynamic polarization (PDP), and cyclic potentiodynamic polarization (CPDP) were employed to assess the effects of adsorption on the corrosion behavior. By demonstrating how rice-derived biomolecules interact with stainless steel and influence corrosion and metal migration, this study addresses a critical knowledge gap in the literature. The insights advance fundamental understanding of food biomolecule–metal interactions and support the design of more durable, compliant, and safe food-contact materials.

Porous polymer-based materials of high electrical conductivity are essential for a wide range of applications. An innovative nanocomposite of V<inf>2</inf>O<inf>5</inf>/rGO/polyaniline hydrogel (VG/PANi-HG) was synthesized using in situ oxidative polymerization in the presence of V<inf>2</inf>O<inf>5</inf>/rGO (VG) and phytic acid on a carbon fiber substrate. Subsequently, the corresponding electrode was employed as a flexible free-standing electrode and examined through a range of electrochemical methods to assess its performance in high-rate supercapacitors. The VG/PANi-HG supercapacitor demonstrated an excellent specific capacitance of 982 F g^–1at a current density of 2.7 A g^–1. Furthermore, an asymmetric all-solid-state (ASC) device was assembled using VG/PANi-HG as a positive electrode in combination with a graphene oxide electrode as a negative electrode and a polyvinyl alcohol (PVA) hydrogel electrolyte. This flexible asymmetric device exhibited an impressive cycle life stability and a power density of 2 kW kg^–1at an energy density of 29.44 Wh kg^–1. Our results reveal that the VG/PANi-HG electrode material is a promising candidate for future electrochemical energy storage devices.

Electrolytic jet machining (EJM) has been widely recognized as one of the effective methods for the surface post-processing of the laser powder bed fusion (LPBF)-components. However, this concept remains challenging due to the limited machining allowance of the LPBF-components and the complexed anodic dissolution behavior, which determine the dimensional accuracy and surface quality of the machined workpiece, respectively. In this work, high current densities ( ≥ 100 A/cm2) are novelly employed to investigate the leveling ratio and transpassive dissolution behavior of LPBF-Inconel 718 for the first time. Compared to 100 A/cm2, 200 A/cm2 improves the leveling ratio to 58.9 % from 57.1 % when the surface roughness is less than 1 µm. However, the high current density up to 200 A/cm2 still cannot inhibit the selective dissolution of the inhomogeneous microstructure, which limits further reduction of the surface roughness. A high current density leads to a rougher micro-surface on horizontal section than low current density, caused by more Nb oxides attached on the horizontal section at high current density generate from continuously distributed Nb-segregation γ phase along the machining depth direction. In addition, the local fine dendrites on vertical section result in a smooth EJM-surface, owing to the relatively uniform dissolution. This investigation provides systematic understanding of leveling process and transpassive dissolution behavior under high current density with complex surface and microstructure, which can further promote synergetic improvements of the surface integrity and dimensional tolerance through controlling the EJM parameters.

Additive manufacturing (AM) using Laser Powder Bed Fusion (L-PBF) enables the fabrication of complex metal components with high precision. However, the as-printed surfaces often exhibit high roughness, residual stresses, and partially fused particles, which can negatively impact the mechanical performance, corrosion resistance, and fatigue life. Surface treatments are therefore required to improve surface integrity, reduce defects, and enhance functional properties such as corrosion resistance. This study explores the impact of chemical and mechanical post-processing methods including pickling, clean hot isostatic pressure (HIP), Hirtization, shot peening (SP), and isotropic super finishing (C.A.S.E.) on the microstructure, surface composition and topography of L-PBF printed HIP treated 316L stainless steel surfaces in relation to their corrosion resistance and extent of metal dissolution in artificial tap water with and without chlorides (1 and 3 wt% Cl⁻). Corrosion studies were also performed in NaCl (2.1 wt% Cl⁻) based on the ASTM G61 standard. The utilization of a combination of electrochemical, chemical, microscopic, and spectroscopic techniques discerned notable differences for the differently surface treated AM 316L in terms of microstructure, surface topography, surface roughness, surface oxide composition and barrier properties, metal dissolution, corrosion resistance as well as pitting corrosion resistance.

The toxicity of micro- and nanoparticles in cell culture studies is influenced by factors like particle size, agglomeration, dissolution of the particles, and methodological factors like sonication protocols. The main aim of this study was to investigate the influence of sonication on the particle size, dissolution, cytotoxicity, and dosing accuracy of nickel (Ni) metal and Ni oxide (NiO) particle dispersions. Such investigations are important to enable studies on the cellular uptake of different Ni substances in lung cells. The effect of sonication was evaluated in ultrapure water, two types of cell media, and A549 human lung cells using the tip and water bath methods. Extended sonication significantly decreased particle size and increased particle dissolution, emphasizing the need for optimized sonication conditions tailored to the specific particle type and study design. Observed findings demonstrate that the sonication step potentially can have a large impact on the results due to changes in particle characteristics, size, and dissolution, properties which are highly dependent on the particle type, solution composition, and sonication parameters. Although only small differences were observed in the limited assessment of cytotoxicity (A549 cells) in this study, further investigation is required to determine the impact of sonication on toxicity. This study also emphasizes the need to evaluate transferred dose samples due to the evident effects of agglomeration, sedimentation, and losses during sample transfer of particle dispersions. The study clearly illustrates that the choice of sonication protocol is particularly critical for toxicity studies, which are the basis of government regulatory decisions and human exposure limits.

Recycling of polymer composites by melt-extrusion has been limited to reinforced thermoplastics. Here, we demonstrate several melt-extrusion recycling cycles for glass fiber-reinforced elastomers cross-linked with a reversible cross-linker (SS). In comparison, reinforced elastomers lacking reversible cross-linking (CC) exhibited clogging during successive melt-extrusion recycling. Furthermore, commercially available starting materials, such as maleated polypropylene (PPgMA), maleated ethylene propylene rubber (EPRgMA), and short-cut glass fibers, were utilized. We showed that when tetrasulfide functionalized glass fibers (SGF) were embedded in SS cross-linked composites (CompSS-SGF), disulfide exchange reactions were further activated. This was manifested in the high tensile strength of 10 MPa and 220% elongation, which were remarkably higher than the 6 MPa and 17% elongation of CC cross-linked composites (CompCC-SGF). Moreover, the higher interactions of CompSS-SGF contributed to at least a 25% increase in tensile strength and storage modulus and a 36% increase in creep resistance compared to composite counterparts prepared with as-received glass fibers (CompSS-AGF) or clean glass fibers (CompSS-CGF). Additionally, the disulfide exchanges in CompSS-SGF possibly contributed to a approximate to 10% higher tensile strength after recycling. This simple up-scalable approach opens new avenues for the development of fiber-reinforced cross-linked elastomers with facile processability, higher dimensional stability, and up-scalable recycling processes.

BackgroundThe eco-corona, consisting of environmental biomolecules formed around engineered nanomaterials (ENMs) when released to the environment, has gained increasing focus in the scientific literature and its role for ENM fate and toxicity is now widely acknowledged. The European chemicals legislation, REACH, entails reporting requirements when it comes to the transformation of nanoforms. Guidance provided by the European Chemicals Agency (ECHA) highlights eco-corona and biotransformation as relevant transformation processes. Still, no specific advice is given on how to test these processes. Based on the findings from the MISTRA Environmental Nanosafety project, we here map out methods to characterise ENM eco-corona and biotransformation and assess their effects. Furthermore, the regulatory relevance of the methods is evaluated.ResultsWe identified methods to assess both eco-coronas formed ex vivo (by interaction with natural organic matter-based solutions or solutions with animal secretes) and bio-coronas formed in vivo (via biotransformation, i.e., filtration of ENMs through living organisms). We recommend implementing these methods and methodological considerations in a future update of ECHA's guidance on ENM ecotoxicity and fate testing, both in the sections on transformation and aquatic pelagic toxicity. When exploring the characteristics and kinetics of eco-corona formation, various data are needed, including data on time-dependent interaction/adsorption/desorption between ENM and constituents in the medium (both with and without the addition of natural organic matter/biomolecules). It is, furthermore, proposed that environmental relevance is enhanced for hazard assessment of nanoforms in REACH. This can be done by incorporating eco-corona considerations in the persistency, bioaccumulative, and toxicity (PBT) assessment.ConclusionsWe here propose to update ECHA 's guidance on ENM ecotoxicity testing and the PBT assessment required under REACH to include eco-corona considerations. If updated, this will aid in implementing information requirements on ENM transformation, increase the environmental relevance of ENM ecotoxicity tests, and reduce uncertainties in the extrapolation of ENM ecotoxicity data.