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.

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.

The use of metal and metal oxide nanomaterials (NMs) is experiencing a significant surge in popularity due to their distinctive structures and properties, making them highly attractive for a wide range of applications. This increases the risks of their potential negative impact on organisms if dispersed into the environment. Information about their behavior and transformation upon environmental interactions in aquatic settings is limited. In this study, the influence of naturally excreted biomolecules from the zooplankton Daphnia magna on nanosized Y2O3 of different concentrations was systematically examined in synthetic freshwater in terms of adsorption and eco-corona formation, colloidal stability, transformation, dissolution, and ecotoxicity towards D. magna. The formation of an eco-corona on the surface of the Y2O3 NMs leads to improved colloidal stability and a reduced extent of dissolution. Exposure to the Y2O3 NMs lowered the survival probability of D. magna considerably. The ecotoxic potency was slightly reduced by the formation of the eco-corona, though shown to be particle concentration-specific. Overall, the results highlight the importance of systematic mechanistic and fundamental studies of factors that can affect the environmental fate and ecotoxic potency of NMs.

The effect of blue light on atmospheric corrosion of Cu and on the antimicrobial properties was explored upon exposure mimicking the condition of hygienic surface disinfection. The results show that blue light illumination enhanced the formation of Cu2O, resulting in a slightly increased corrosion resistance of Cu without pre-deposited NaCl, whereas the enhanced formation of Cu2O, CuCl and/or Cu(OH)3Cl on copper with pre-deposited NaCl caused concomitant corrosion product flaking and a reduced corrosion resistance. The blue light induced enhancement of Cu corrosion led to increased surface roughness and more pronounced integration of bacteria within the corrosion products.

Expanding applications and production of engineered nanoparticles lead to an increased risk for their environmental dispersion. Systematic knowledge of surface transformation and dissolution of nanoparticles is essential for risk assessment and regulation establishment. Such aspects of Co- and Ni-based nanoparticles including metals, oxides, and solution combustion synthesized metal nanoparticles (metal cores with carbon shells) were investigated upon environmental interaction with organic matter, simulated by natural organic matter (NOM) and degradation products from zooplankton and algae (eco-corona biomolecules, EC) in freshwater (FW). The presence of NOM and EC in FW results in negative surface charges of the nanoparticles reduces the extent of nanoparticles agglomeration, and increases concentration, mainly due to the surface adsorption of carboxylate groups of the organic matter. The dissolution of the Co-based nanoparticles was for all conditions (FW, FW with NOM or EC) higher than the Ni-based, except for Co3O4 being nearly non-soluble. The surface transformation and dissolution of nanoparticles are highly exposure and time-dependent, and surface- and environment specific. Therefore, no general correlation was observed between dissolution and, particle types, surface conditions, or EC/NOM adsorption. This underlines the importance of thorough investigations of nanoparticles adsorption/desorption, degradation, and exposure scenarios for developing regulatory relevant protocols and guidelines.

Humans can be exposed to engineered and nonintentionally formed metal and metal oxide nanoparticles (Me NPs) in occupational settings, in public transportation areas, or by means of contact with different consumer products. A critical factor in the toxic potency of Me NPs is their ability to induce oxidative stress. It is thus essential to assess the potential reactive oxygen species (ROS) formation properties of Me NPs. A common way to assess the relative extent of ROS formation in vitro is to use fluorescence spectroscopy with the DCFH-DA (2 ',7'-dichlorofluorescein diacetate) probe, with and without HRP (horseradish peroxidase). However, this method does not provide any information about specific ROS species or reaction mechanisms. This study investigated the possibility of using complementary techniques to obtain more specific information about formed ROS species, both the type and reaction mechanisms. Cu NPs in PBS (phosphate buffered saline) were chosen as a test system to have the simplest (least interference from other components) aqueous solution with a physiologically relevant pH. ROS formation was assessed using fluorescence by means of the DCFH-DA method (information on relative amounts of oxygen radicals without selectivity), the Ghormley's triiodide method using UV-vis spectrophotometry (concentrations of H2O2), and electron paramagnetic resonance with DMPO as the spin-trap agent (information on specific oxygen radicals). This approach elucidates that Cu NPs undergo ROS-generating corrosion reactions, which previously have not been assessed in situ. In the presence of H2O2, and based on the type of oxygen radical formed, it was concluded that released copper participates in Haber-Weiss and/or Fenton reactions rather than in Fenton-like reactions. The new combination of techniques used to determine ROS induced by Me NPs provides a way forward to gain a mechanistic understanding of Me NP-induced ROS formation, which is important for gaining crucial insight into their ability to induce oxidative stress.

Increased use and production of engineered nanoparticles (NPs) lead to an elevated risk of their diffuse dispersion into the aquatic environment and increased concern on unknown effects induced by their release into the aquatic ecosystem. An improved understanding of the environmental transformation processes of NPs of various surface characteristics is hence imperative for risk assessment and management. This study presents results on effects of natural organic matter (NOM) on the environmental transformation and dissolution of metal and metal oxide NPs of different surface and solubility properties in synthetic freshwater (FW) with and without NOM. Adsorption of NOM was evident on most of the studied NPs, except Sb and Sb2O3, which resulted in the formation of negatively charged colloids of higher stability and smaller size distribution compared with the same NPs in FW only. The dissolution rate of the NPs in the presence of NOM correlated with the strength of interactions between the carboxylate group of NOM and the particle surface, and resulted in either no (Mn, Sb, ZnO NPs), increased (Co, Sn NPs) and decreased (Ni, NiO, Sb2O3, Y2O3 NPs) levels of dissolution. One type of metal NP from each group (Mn, Ni, Sn) were investigated to assess whether observed differences in adsorption of NOM and dissolution would influence their ecotoxic potency. The results showed Mn, Ni, and Sn NPs to generate intracellular reactive oxygen species (ROS) in a time and dose-dependent manner. The extent of ROS generation in FW was similar for both Mn and Ni NPs but higher for Sn NPs. These findings are possibly related to interactions and infiltration of the NPs with the cells, which lead to redox imbalances which could induce oxidative stress and cell damage. At the same time, the presence of NOM generally reduced the intracellular ROS generation by 20-40% for the investigated NPs and also reduced cytotoxicity of Sn NPs, which can be attributed to the stronger interaction of carboxylate groups of NOM with the surface of the NPs.

Diffusely dispersed metal and metal oxide nanoparticles (NPs) can adversely affect living organisms through various mechanisms and exposure routes. One mechanism behind their toxic potency is their ability to generate reactive oxygen species (ROS) directly or indirectly to an extent that depends on the dose, metal speciation, and exposure route. This review provides an overview of the mechanisms of ROS formation associated with metal and metal oxide NPs and proposes a possible way forward for their future categorization. Metal and metal oxide NPs can form ROS via processes related to corrosion, photochemistry, and surface defects, as well as via Fenton, Fenton-like, and Haber-Weiss reactions. Regular ligands such as biomolecules can interact with metallic NP surfaces and influence their properties and thus their capabilities of generating ROS by changing characteristics such as surface charge, surface composition, dissolution behavior, and colloidal stability. Interactions between metallic NPs and cells and their organelles can indirectly induce ROS formation via different biological responses. H2O2 can also be generated by a cell due to inflammation, induced by interactions with metallic NPs or released metal species that can initiate Fenton(-like) and Haber-Weiss reactions forming various radicals. This review discusses these different pathways and, in addition, nano-specific aspects such as shifts in the band gaps of metal oxides and how these shifts at biologically relevant energies (similar to activation energies of biological reactions) can be linked to ROS production and indicate which radical species forms. The influences of kinetic aspects, interactions with biomolecules, solution chemistry (e.g., Cl- and pH), and NP characteristics (e.g., size and surface defects) on ROS mechanisms and formation are discussed. Categorization via four tiers is suggested as a way forward to group metal and metal oxide NPs based on the ROS reaction pathways that they may undergo, an approach that does not include kinetics or environmental variations. The criteria for the four tiers are based on the ability of the metallic NPs to induce Fenton(-like) and Haber-Weiss reactions, corrode, and interact with biomolecules and their surface catalytic properties. The importance of considering kinetic data to improve the proposed categorization is highlighted.

Increasing the use of hygienic high-touch surfaces with antimicrobial properties in health care and public spaces is one way to hinder the spread of bacteria and infections. This study investigates the antimicrobial efficacy and surface reactivity of commercial laminate and powder coated surfaces treated with silver-doped phosphate glass as antimicrobial additive towards two model bacterial strains, Escherichia coli and Bacillus subtilis, in relation to surface weathering and repeated cleaning. High-touch conditions in indoor environments were simulated by different extents of pre-weathering (repeated daily cycles in relative humidity at constant temperature) and simplified fingerprint contact by depositing small droplets of artificial sweat. The results elucidate that the antimicrobial efficacy was highly bacteria dependent (Gram-positive or Gram-negative), not hampered by differences in surface weathering but influenced by the amount of silver-doped additive. No detectable amounts of silver were observed at the top surfaces, though silver was released into artificial sweat in concentrations a thousand times lower than regulatory threshold values stipulated for materials and polymers in food contact. Surface cleaning with an oxidizing chemical agent was more efficient in killing bacteria compared with an agent composed of biologically degradable constituents. Cleaning with the oxidizing agent resulted further in increased wettability and presence of residues on the surfaces, effects that were beneficial from an antimicrobial efficacy perspective.

Metal-based high-touch surfaces used for indoor applications such as doorknobs, light switches, handles and desks need to remain their antimicrobial properties even when tarnished or degraded. A novel laboratory methodology of relevance for indoor atmospheric conditions and fingerprint contact has therefore been elaborated for combined studies of both tarnishing/corrosion and antimicrobial properties of such high-touch surfaces. Cu metal was used as a benchmark material. The protocol includes pre-tarnishing/corrosion of the high touch surface for different time periods in a climatic chamber at repeated dry/wet conditions and artificial sweat deposition followed by the introduction of bacteria onto the surfaces via artificial sweat droplets. This methodology provides a more realistic and reproducible approach compared with other reported procedures to determine the antimicrobial efficiency of high-touch surfaces. It provides further a possibility to link the antimicrobial characteristics to physical and chemical properties such as surface composition, chemical reactivity, tarnishing/corrosion, surface roughness and surface wettability. The results elucidate that bacteria interactions as well as differences in extent of tarnishing can alter the physical properties (e.g. surface wettability, surface roughness) as well as the extent of metal release. The results clearly elucidate the importance to consider changes in chemical and physical properties of indoor hygiene surfaces when assessing their antimicrobial properties.