Magnetic iron oxide nanoparticles: An emerging threat for the environment and human health

Magnetic iron oxide nanoparticles (FexOy NPs, mainly Fe3O4 and γ-Fe2O3) are nanomaterials ubiquitously present in aquatic, terrestrial, and atmospheric environments, with a high prevalence and complex sources. Over the past decade, numerous reports have emerged on the presence of exogenous particles in human body, facilitated by the rapid development of separation and detection methods. The health risk associated with magnetic FexOy NP have garnered escalating attention due to their presence in human blood and brain tissues, especially for their potential association with neurodegenerative diseases like Alzheimer's disease. In this paper, we provide a comprehensive overview of sources, analysis methods, environmental impacts, and health risks of magnetic FexOy NP. Currently, most researches are primarily based on engineered FexOy NP, while reports about magnetic FexOy NP existing in real-world environments are still limited, especially for their occurrence levels in various environmental matrices, environmental transformation behavior, and biotoxic effects. Our study reviews this emerging pollutant, providing insights to address current research deficiencies and chart the course for future studies.

Robust polyaniline coating magnetic biochar nanoparticles for fast and wide pH and temperature range removal of nanoplastics and achieving label free detection

Nanoplastics as an emerging pollutant are ubiquitous in water and still not easy to measure and remove. In this regard, polyaniline coating magnetic biochar nanoparticles constructed by pyrolysis of ferrate pretreated bagasse and ball milling and coating surface with polyaniline (PA@MBCBM) were tested for their capability to attach and remove polystyrene nanoplastics in water. Porousness and rich functional groups and positive charging property of PA@MBCBM was responsible for fast, high capacity and robust attaching of nanoplastics. 94.9 % - 99.0 % of nanoplastics were removed at wide range of pH conditions (1 - 10) and PA@MBCBM was reusable for seven times with less changing of performance, and maximum adsorption capacities reached 276.24 - 334.45 mg/g at both cold and warm temperatures (5 - 35 °C). Moreover, taking advantages of efficient nanoplastics adhesion, high conductivity and electrochemical activity, the PA@MBCBM, was tested to fabricate a label free screen-printed electrode for nanoplastics detection, and achieved reasonable sensitivity with the lowest detection limit being 1.26 μg/L. In addition, exceptional performances of adsorption and detection in real water samples were also successfully realized. The proposed PA@MBCBM having dual function of robust and efficient adsorption removal, and label free and sensitive determination of nanoplastics, would be greatly constructive for reliable, cost effective and effective control and monitoring of the nanoplastics contamination.

Copper oxide nanoparticles induce pulmonary inflammation via triggering cellular cuproptosis

Copper oxide nanoparticles (CuO NPs) are increasingly used in various industrial fields, and the toxicity of CuO NPs raises concerns. However, the CuO NPs-induced pulmonary inflammation and the underlying mechanism have not been fully illustrated. Cellular cuproptosis provides a new perspective to elucidate the toxicity of CuO NPs. Here, we exposed C57BL/6 mice and murine alveolar macrophage cells (MH-S) to CuO NPs, respectively. A suspension of 2 mg/mL CuO NPs was directly once administered by intratracheal instillation, and mice were sacrificed on day 7. The histopathology results showed that CuO NPs induced pulmonary inflammation in C57BL/6 mice. CuO NPs increased Cu2 + levels by 203.0 % in mouse lung tissues. Also, CuO NPs increased the cuproptosis-related indicators of ferredoxin (FDX1), dihydrolipoamide succinyltransferase (DLST), dihydrolipoamide acetyltransferase (DLAT) and Cu transporter 1 (CTR1) in both mouse lung tissues and MH-S cells. Transcript sequencing and non-targeted metabolomics indicated that CuO NPs induced cellular cuproptosis and inflammatory responses both in vivo and in vitro. Interleukin-17a (IL-17A) was remarkably increased in the process of CuO NPs-induced cellular cuproptosis. Additionally, interference of FDX1 reduced cellular cuproptosis and decreased the release of IL-17A. In summary, CuO NPs increased the accumulation of intracellular Cu2+ and the expressions of cuproptosis-related proteins, induced FDX1-mediated cuproptosis, and led to pulmonary inflammation in mice. This study highlights the respiratory toxicity of CuO NPs and reveals a unique cuproptosis-driven mechanism underlying the CuO NPs-induced pulmonary inflammation.

The fate of cadmium during the hydrolysis and solid-state transformation of iron

The ubiquitous hydrolysis of Fe(III) ions in nature leads to the formation of ferrihydrite (Fh), which then undergoes solid-state transformation into crystalline mineral phases. However, the impact of this process on the geochemical fate of cadmium (Cd) in aquatic environments is not yet fully understood. This investigation systematically examined the partitioning mechanisms of Cd during the aforementioned processes through extraction techniques and multiple characterization methodologies. The experimental results demonstrated that Fe(III) ions first undergo the diffusion-limited aggregation (DLA) stage, forming loosely bound clusters with high Cd co-precipitation capacity. Upon transitioning to the reaction-limited aggregation (RLA) stage, Fe clusters exhibit increased structural complexity, wherein the expansion of radius of gyration predominantly governs Cd retention. As colloidal Fh develops, surface adsorption becomes the predominant mechanism for Cd sequestration. Throughout solid-state transformation in systems containing 1 mol% Cd, dehydroxylation processes induced acidification, facilitating the progressive liberation of Cd. Conversely, in systems with 10 mol% Cd, significant Cd incorporation induces distortion in the crystalline lattice structure, promoting system alkalinization and, consequently, enhancing Cd immobilization. pH gradient solid-state transformation experiments demonstrated that when initial pH values were below 8, final pH measurements were significantly lower than initial values, and vice versa. pH conditions potentially regulate the speciation of Fe within Fh, ultimately exerting substantial influence on Cd partitioning behavior. In summary, Fh formation beneficially stabilizes Cd, while its subsequent solid-state transformation triggers Cd redistribution.

Natural, Incidental, and Engineered Nanomaterials in Surface Waters: Occurrence and Catalytic Reactivity Influences on Micropollutant Degradation Plus Nutrient Turnover

Nanomaterials (NMs)─whether natural, incidental, or engineered─are now documented to occur in aquatic environments, with concentrations of elements such as titanium, cerium, and palladium exceeding tens of parts per billion. While prior research has emphasized the toxicology of engineered NMs, their broader geochemical roles remain underexplored. Catalytically active NMs can influence key environmental processes, such as nutrient cycling and pollutant degradation, through photocatalytic, hydrolytic, and hydrogenation mechanisms. Reactive oxygen species (ROS) (including hydroxyl radicals, singlet oxygen, and hydrogen peroxide) produced via UVA or visible light photocatalysis on NM surfaces drive important transformations. Steady-state ROS concentrations (0.1-10 fM) are comparable to those from excited-state dissolved organic matter (DOM*). NMs can hydrolyze and facilitate the conversion of organic phosphorus to bioavailable inorganic forms or organic carbon to low-molecular-weight compounds, potentially fueling microbial food webs. However, major gaps remain regarding NM diversity, reactivity, and persistence. Addressing these requires integrating advanced nanoanalytical tools (e.g., ICP-MS, electron microscopy with EELS) and functional reactivity assays applied to environmentally sourced NMs over ecologically relevant time scales of days to months. This Perspective highlights NMs as dynamic, transient components of aquatic systems introduced through deposition, runoff, and biogenic activity, with implications for global biogeochemical cycling.

Recyclable Supramolecular Nanofibrous Composite Membranes for Efficient Air Filtration

Developing high-performance, low-resistance, and recyclable air filtration materials remains a formidable challenge. Herein, silica nanoparticles (SiO2 NPs) and supramolecular complexes consisting of melamine (MA) and trimesic acid (TMA) are constructed as SiO2@MA·TMA supramolecular nanofibrous composite membrane via a thermally induced precursor process (TIPC) for efficient particulate matter (PM) removal. Hydrophilic SiO2 NPs as additional nucleation mediators can not only promote the growth of MA·TMA nanocrystalline fibers by shortening the interfacial free energy and thus reducing the nucleation barrier, but also increase fiber surface roughness thus constructing hierarchical structure of membrane. Under the synergy of MA·TMA nanocrystalline fibers and SiO2 NPs, the membranes possess high filtration efficiency of 99.82% for PM1, 99.96% for PM2.5, and 99.98% for PM10 with low air resistance (153 Pa, <0.15% of standard atmospheric pressure). Taking advantage of the thermally reversible property of supramolecular complexes, the closed-loop recycling of MA·TMA nanocrystalline fibers and SiO2 NPs are realized. Only green solvents (water and ethanol) are involved in the TIPC process, making this strategy environmentally-friendly and cost-effective. This work not only provides an innovative strategy for the preparation of supramolecular nanofibrous composite materials, but opens an avenue for the development of recyclable high-performance air filters.

Size-dependent internalization of gold nanoparticles in individual Tetrahymena thermophila characterized by single-cell mass cytometry

Aquatic organisms are inevitably exposed to metallic nanoparticles (NPs) in natural environments, leading to potential harm, ecological disruption, and environmental pollution concerns. Importantly, the size of NPs plays a critical role in influencing their uptake by these organisms. Utilizing mass cytometry, we investigated the internalization characteristics of different-sized gold NPs (AuNPs) in an unicellular ciliate Tetrahymena thermophila, under a low exposure concentration of 1 ngmL-1. This investigation, conducted at both the population and single-cell levels, revealed that the size of AuNPs significantly affected their uptake by T. thermophila cells. The average mass of intracellular AuNPs peaked at 0.5 h and subsequently decreased, attributed to the efflux of AuNPs or cell proliferation. Larger AuNPs resulted in a lower average intracellular AuNPs mass and a smaller proportion of T. thermophila cells accumulating AuNPs (Au-positive (AuP) T. thermophila). However, when exposed to larger AuNPs, the AuPT. thermophila cells had a higher AuNPs mass and volumetric concentration factors compared to their exposure to smaller AuNPs. After exposure, while most AuPT. thermophila cells had intracellular Au content below 2.41 × 10-15 g cell-1, the small groups of T. thermophila cells that accumulated higher mass of AuNPs may be the ones more susceptible to the effects of AuNPs exposure. Additionally, we developed a three-dimensional fitting surface model to depict the relationship among exposure time, AuNP size, and intracellular AuNPs mass in individual T. thermophila cells. This study enhances our understanding of size-specific NPs accumulation in unicellular organisms and provides valuable insights for ecological risk assessment of different sized NPs.

Size Distribution of Micro-/Nanoplastic Particles and Their Chemical Speciation in the Atmosphere of Shanghai, China

The significance of microplastics in urban air has gained increasing recognition; however, a comprehensive understanding of their size distribution and composition remains limited. This study presents analyzed results of micro-/nanoplastics collected from Shanghai's winter atmosphere using thermal desorption/pyrolysis-gas chromatography-mass spectrometry. Six major plastic types were identified, with polyethylene (PE) accounting for 40.0% of the detected atmospheric plastics. Fine plastic particles (FPPs, ≤3.2 μm) constituted 59.2% of the total mass concentration of microplastics (MPs), while nanoplastics (NPs, ≤1.0 μm) accounted for 36.3%. As the aerodynamic particle size decreased, the proportion of plastics other than PE increased. This size-dependent compositional variation suggests that nanoplastics, due to their smaller size, can more easily penetrate sensitive biological regions. At the nanoscale, the accumulated mass in pulmonary regions exceeds that in the head airway. These findings underscore the critical need for detailed assessments of plastic characteristics in the atmosphere to better understand their environmental behavior and potential health impacts.

Aggregation and sedimentation kinetics of nano-TiO2 in Daihai Lake: Mechanisms influenced by pH, natural organic matter, and ions based on interaction energy

The widely used nano-TiO2 particles were selected to investigate the aggregation and sedimentation in simulated solutions with different humic acid (HA), cations (Na+, Ca2+, Mg2+) and pH value by measuring zeta potential, hydrodynamic diameter (HDD) and A/A0. Notably, the extended Derjaguin Landau Verwey Overbeek (XDLVO) theory was used to calculate the interaction energy between nano-TiO2 particles to reveal the influence of various factors on aggregation and sedimentation mechanistically. Additionally, the aggregation and sedimentation of nano-TiO2 in natural water from Daihai Lake were determined to verify the applicability of the XDLVO theory in actual water. Results showed that HA inhibits the sedimentation of nano-TiO2 in Na + solution by steric hindrance, while induces rapid aggregation in Mg2+ or Ca2+ solutions due to cation bridging. Change of pH value had little effect on sedimentation performance of nano-TiO2 in solution contain cations and HA. Furthermore, nano-TiO2 were more stable in water sample of Daihai Lake with the A/A0 range from 0.83 to 0.88. And the poor sedimentation performance of nano-TiO2 is result from influence of dissolved organic carbon (DOC) and Na+. These findings are important for evaluating the behavior of nanoparticles in natural water.

Effect of Polydopamine-Coated Strontium-Doped Hydroxyapatite Nanowires on Bone Marrow Mesenchymal Stem Cells and Umbilical Vein Endothelial Cells

Hydroxyapatite nanowires (HAW) can effectively improve the bone repair ability in bone engineered tissue. However, due to their single function, the application of HAWs in biological tissue engineering materials is limited. In this study, strontium-doped hydroxyapatite nanowires (SrHAW) were synthesized by a hydrothermal method and coated with polydopamine (PDA) to improve the function of HAWs. The material structure, biocompatibility evaluation, and differentiation capability testing of PDA-coated strontium-doped hydroxyapatite (SrHAW@PDA) nanowires were conducted. Then, the nanowires were co-cultured with rat bone marrow mesenchymal stem cells (BMSCs) and rat umbilical vein endothelial cells (UVECs) to prepare cell spheroids. Compared with the undoped and uncoated HAW, the SrHAW@PDA nanowires enhanced the cell activity and their angiogenesis and osteogenesis abilities. In addition, their performance in the three-dimensional spheroid also played a positive role in the cells in the spheroid. Due to the presence of PDA, the adhesion between the cells in the three-dimensional spheroid and the nanowires were enhanced. In summary, these results show that SrHAW@PDA has the potential to be used as an alternative material to regulate cell biological activity in three-dimensional cell spheroids.

Inhaled Lead Nanoparticles Enter the Brain through the Olfactory Pathway and Induce Neurodegenerative Changes Resembling Tauopathies

Lead nanoparticles (PbNPs) in air pollution pose a significant threat to human health, especially due to their neurotoxic effects. In this study, we exposed mice to lead(II) oxide nanoparticles (PbONPs) in inhalation chambers to mimic real-life exposure and assess their impact on the brain. PbONPs caused the formation of Hirano bodies and pathological changes related to neurodegenerative disorders through cytoskeletal disruptions without the induction of inflammation. Damage to astrocytic endfeet and capillary endothelial cells indicated a compromised blood-brain barrier (BBB), allowing PbONPs to enter the brain. Additionally, NPs were detected along the olfactory pathway, including fila olfactoria, suggesting that at least a proportion of PbNPs enter the brain directly by passing through the olfactory epithelium. PbNP inhalation severely damaged the apical parts of olfactory epithelial cells, including the loss of microtubules in their ciliary distal segments. Inhalation of PbONPs led to the rapid accumulation of lead in the brain, while more soluble lead(II) nitrate NPs did not accumulate significantly until 11 weeks of exposure. PbNPs induced disruption of the BBB at multiple levels, ranging from ultrastructural changes to functional impairments of the barrier; however, they did not induce systemic inflammation in the brain. The clearance ability of the brain to remove Pb was very low for both types of NPs, with significant pathological effects persisting even after a long clearance period. Cation-binding proteins (ZBTB20 and calbindin1) were distributed unevenly in the brain, with the strongest signal located in the hippocampus, which exhibited the greatest defects in nuclear architecture, indicating that this area is the most sensitive structure for PbNP exposure. PbNP exposure also altered the PI3K/Akt/mTOR signaling pathway, and tau phosphorylation in the hippocampus and inhibition of tau phosphorylation by GSK-3 inhibitor rescued the negative effect of PbONPs on the intracellular calcium level in trigeminal ganglion cultures. In zebrafish larvae, PbONPs affected locomotor activity and reduced calcium levels in the medium enhanced negative effect of PbONP on animal mobility, even increasing lethality. These findings suggest that cytoskeletal disruption and calcium dysregulation are key factors in PbNP-induced neurotoxicity, providing potential targets for therapeutic intervention to prevent neurodegenerative changes following PbNP exposure.

Deposition of Air Pollution-Derived Magnetic Nanoparticles in Human Kidney Revealed by High-Resolution Microstructural Characterization

Exposure to air pollutants, especially fine particulate matter (PM2.5), has been recognized as a major contributor to the increasing prevalence of kidney diseases. However, until now, evidence for the translocation of airborne nanoparticles (NPs) in the human kidney has been lacking, hindering the understanding of the relationships between PM2.5 exposure and kidney diseases. Here, we report the discovery and analysis of airborne magnetite nanoparticles in human kidney stones (with mass concentrations ranging from 363 to 740 ng/g dry tissue weight) by high-resolution microstructural characterization. Notably, we established a methodology for highly selective extraction and accurate characterization of distinctive magnetite NPs and identified the abundant presence of these NPs with a distinctive core-shell structure of Fe3O4/SiO2 in both kidney stones and human blood. We demonstrate that such distinctive core-shell magnetite NPs are indicative of a coal-burning source. Hence, magnetite NPs deposited in the human kidneys in this study area most likely derived from air pollution emissions from coal-fired power plants and were transported via blood circulation to the kidney. Our results provide compelling evidence for understanding the systemic health risks of exposure to nanoparticulate, Fe-bearing air pollution and the associations observed between kidney diseases and PM2.5 exposure.

Efficient extraction and analysis method for lead-containing nanoparticles in complex biological samples to eliminate "false" interferences by using SP-ICP-MS

Metal-containing nanoparticles (MNPs) ubiquitously exist in the environment and organisms, playing distinct roles in the fate and toxicity of metals. However, the extraction and analysis of the MNPs in biological samples is still a great challenge and the interferences of other metal species and complex matrices remains unclear. In this work, we established a method for efficient extraction and accurate analysis of MNPs in biological samples to eliminate the interference caused by metal ions and biological matrices based on the alkali extraction and single particle mode inductively coupled plasma mass spectrometry (SP-ICP-MS). Obvious interference signals of lead-containing nanoparticles (PbNPs) were found in various biological matrices (liver, brain, bile, intestine, stomach), causing false positive results or overestimation of PbNPs. Then, a novel strategy using EDTA and ultrasonic during the TMAH extraction process were proposed to successfully eliminate the interferences due to the strong and competitively binding of EDTA to Pb ions, which was identified as ionic signals in SP-ICP-MS and resulted in the elimination of interferences. Finally, this method was successfully applied for the extraction, characterization and quantification of PbNPs in different biological tissues collected near a power plant, revealing the occurrence of PbNPs in stomach, intestine and liver tissues and indicating their oral exposure and potential translocation. This method could be universally applied for the efficient extraction and accurate analysis of MNPs in biological samples and thus provided a reliable and powerful tool for the investigation of the occurrence, fate and toxicity of MNPs in environmental and organisms.

Nano-Scale Insights into Clay Minerals Regulating the Fe(II)-Catalyzed Ferrihydrite Transformation under Anoxic Conditions

Metastable ferrihydrite nanoparticles and clay minerals always coexist as heteroaggregates in nature due to their abundance, opposite charge, and large interface energy. However, the impact of clay minerals on the transformation of ferrihydrite under anoxic conditions remains elusive. This study systematically investigated the effect of distinct clay minerals on the Fe(II)-catalyzed transformation of ferrihydrite and clarifying the underlying nanoscale mechanisms for the first time. Our results demonstrated that clay minerals could affect the production and recrystallization of labile Fe(III) (an active Fe(III) intermediate species formed by oxidation of Fe(II) at the ferrihydrite surface) by dispersing ferrihydrite aggregates. This modulation led to different transformation rates, higher crystallinity of formed lepidocrocite, and enhanced goethite formation in the heteroaggregates. Importantly, montmorillonite can accommodate Fe(II) and labile Fe(III) within its interlayer spaces, which further led to the inhibited crystallization of Fe(II) to magnetite and long-term preservation of labile Fe(III). Additionally, clay minerals served as templates for forming dendritic goethite and hexagonal magnetite nanoplates. Our findings provide new insights into the complicated roles of clay minerals in controlling the ferrihydrite transformation and other iron (oxyhydr)oxides formation, which is significant for predicting the bioavailability of iron and the fate of other coexisting contaminants.

Phytoremediation of nanoparticles, as future water pollutants, using aquatic and wetland plants: Feasibility, benefits and risks, and research gaps

The widespread use of nanoparticles (NPs) in recent years and their rapid accumulation as potentially dangerous pollutants can lead to significant environmental risks. Different methods are used to eliminate emerging contaminants such as NPs from aquatic environments. Of these methods, phytoremediation using aquatic and wetland plants (WAPs) is considered the most suitable approach because of their extensive root systems, high rates of biomass production, ability to thrive in diverse habitats, and rapid growth within aquatic ecosystems. Various species of genera Lemna, Salvinia, Spirodela, Phragmites, Elodea, and Pistia have been studied for their potential to remediate NPs or contaminants released by NPs. The findings of the review indicate that the majority of WAPs cannot accumulate NPs within their tissues. Nevertheless, the effective methods for removing NPs from the environment by WAPs involve the surface adsorption of NPs onto their roots and the accumulation of pollutants released by NPs within the plant tissues. In addition to the benefits of NPs phytoremediation through WAPs, including sustainability, efficiency, and affordability, there are risks to consider, such as the potential transfer of NPs into the food chain, the release of toxic compounds from NPs due to (bio)degradation, and interactions between contaminated WAPs and other ecosystem components. Furthermore, several research gaps need to be addressed in the future, including a scarcity of field studies, a limited focus on NP types and plant species, unrealistic NP concentration, comparisons with bulk materials, the use of additives and amendments, and the genetic engineering of WAPs.

High-Fidelity Computational Microscopy via Feature-Domain Phase Retrieval

Computational microscopy enhances the space-bandwidth product and corrects aberrations for high-fidelity imaging by reconstructing complex optical wavefronts. Phase retrieval, a core technique in computational microscopy, faces challenges maintaining consistency between physical and real-world imaging formation, as physical models idealize real phenomena. The discrepancy between ideal and actual imaging formation limits the application of computational microscopy especially in non-ideal situations. Here, the feature-domain consistency for achieving high-fidelity computational microscopy is introduced. Feature-domain consistency tells that certain features, such as edges, textures, or patterns of an image, remain invariant in different image transformations, degradations, or representations. Leveraging the feature-domain consistency, Feature-Domain Phase Retrieval (FD-PR) is proposed, a framework applicable to various computational microscopy. Instead of working directly with images' pixel values, FD-PR uses image features to guide the reconstruction of optical wavefronts and takes advantage of invariance components of images against mismatches of physical models. Experimental studies, across diverse phase retrieval microscopic tasks, including coded/Fourier ptychography, inline holography, and aberration correction, demonstrate that FD-PR improves resolution by a factor of 1.5 and reduces noise levels by a factor of 2. The proposed framework can immediately benefit a wide range of computational microscopies, such as X-ray ptychography, diffraction tomography, and wavefront shaping.

Epipelagic community as prominent biosensor for sub-micron and nanoparticles uptake: Insights from field and laboratory experiments

Nowadays, ENMs/NPLs particles have not yet been extensively measured in the environment, but there is increased concern that this size fraction may be more widely distributed and hazardous than larger-sized particles. This study aimed to examine the bioaccumulation potential of engineered nanomaterials and nanoplastics (ENMs/NPLs) across marine food webs, focusing on plankton communities and commercial fish species (Engraulis encrasicolus and Scomber colias) from the Gulf of Naples. Laboratory experiments on plankton assemblages exposed to fluorescent polystyrene nanoplastics (PS-NPs, 100 nm) for 24h at concentrations ranging from 0.01 to 10 mg/L confirmed nanoplastic uptake in phytoplankton and zooplankton, indicating a dose-dependent internalization in plankton communities. Notably, in natural samples no particles were detected in fish muscle or liver tissues, suggesting limited translocation. Unexpectedly, titanium oxide particles (<1 μm) were found in natural phytoplankton, highlighting the potential presence of other nanoparticles in marine systems. These findings suggest that, despite detection challenges, plankton communities are major biosensors of ENMs/NPs contamination and highlight the need for ongoing environmental monitoring to assess ecological impacts and potential risks of nanoparticle bioaccumulation in marine ecosystems.

Size-Dependent Reduction Kinetics of Iron Oxides in Single and Mixed Mineral Systems

Iron(III) (oxyhydr)oxide minerals with varying particle sizes commonly coexist in natural environments and are susceptible to both chemical and microbial reduction, affecting the fate and mobility of trace elements, nutrients, and pollutants. The size-dependent reduction behavior of iron (oxyhydr)oxides in single and mixed mineral systems remains poorly understood. In this study, we used microbial and mediated electrochemical reduction approaches to investigate the reduction kinetics and extents of goethite and hematite. We found that small particles were preferentially reduced relative to their large counterparts in single and mixed mineral systems regardless of microbial or electrochemical treatments, which is attributed to the combined effect of higher thermodynamic favorability and greater surface availability. In mixed mineral systems, small particles were reduced slightly faster, whereas large particles were reduced notably slower and less extensively than solely predicted from single mineral systems. Specifically, when reduced alone, small particles showed Fe(III) reduction rate constants that were 1.5- to 3.6-fold higher than large particles, while when reduced together, the reduction rate constants for small particles were 6- to 21-fold higher than the rate constants for large particles. These collective findings provide new insights into the pivotal role of nanoparticulate iron (oxyhydr)oxides in environmental redox reactions.

Distribution and source of titanium dioxide nanoparticles in seawater and sediment from Jiaozhou Bay, China

The widespread use of titanium dioxide nanoparticles (TiO2NPs) and their potential adverse effects on the ecosystems have raised significant concerns. Limitations in detection methods and insufficient data on their environmental concentrations, especially in marine systems, hinder the accurate risk assessment. Herein, a robust method for the analysis of TiO2NPs in marine sediment is developed, with a detection limit of 0.09 μg/g. The spatial distribution of TiO2NPs in seawater and sediments in Jiaozhou Bay was investigated. High concentrations of TiO2NPs in seawater were distributed in the northeastern region, near river inlets and sea-crossing bridges. By using the proposed method, the mass concentrations of TiO2NPs in the Jiaozhou Bay sediments were first reported, ranging from 0.697 to 2.44 mg/g. There was no positive correlation between the distribution of TiO2NPs in seawater and sediment. The Ti/Nb ratio of TiO2NPs was used to distinguish whether TiO2NPs were sourced from the background or anthropogenic inputs. Similar distribution trends of Ti/Nb ratios in seawater and sediment suggest that significant engineered TiO2NPs were transferred from high-salinity seawater to sediment via agglomeration and sedimentation. Industrial discharges and bridge runoff may be primary contributors of engineered TiO2NPs. This study provides a reliable method for the analysis of TiO2NPs in marine sediment, which would contribute to tracking the mobility of TiO2NPs in the marine system. The data on the spatial distribution and possible sources of TiO2NPs in Jiaozhou Bay also benefit the risk assessment and control.

Volcanic aerosols captured by plants: A study of nanoparticles and their chemical composition

Nanoparticles (NPs) exhibit high reactivity and mobility in the environment, and a significant capacity to penetrate living organisms, potentially leading to harmful effects. Volcanoes are the second major source of natural NPs emitted into the atmosphere, with an estimated flux of 342 Tg/year. Few studies have focused on their fate. Thanks to technological advances in single-particle inductively coupled plasma mass spectrometry (spICP-MS), this trend is starting to reverse. La Soufrière volcano in Guadeloupe, chosen as a case study, exhibits increasing hydrothermal activity since its last eruption in 1530. This study aims to characterize NPs produced during volcanic activity by analysing ancient ash deposits, as well as those formed during periods of volcanic inactivity by examining condensates near fumaroles, as ultrafine particles are primarily generated through gas condensation. In this study, plants are utilized as samplers for NPs produced by fumarole activity. The use of a ICP-MS time-of-flight in single particle mode (spICP-ToF-MS), combined with data processing techniques such as hierarchical agglomerative clustering, enables the detailed characterization of NPs by determining their multi-element composition, concentration, and mass distribution. The results demonstrate that plants can effectively serve as samplers, even under the extreme environmental conditions present at the volcano's summit. However, differences in their efficiency at trapping particles on leaf surfaces can be attributed to varying physical characteristics of the plants. The spICP-ToF-MS analysis identified three types of multi-elemental NPs (NP-Al + Si, NP-Al + Fe, NP-Ti + Al) and three mono-elemental NPs (NP-Al, NP-Si, NP-Fe). Additionally, NPs containing trace elements were detected exclusively in undiluted Sphagnum pore water, where one tri-elemental NP (Sr-Ce-La), one bi-elemental NP (CeLa), and nine mono-elemental NP families (Cr, Cu, Zn, Sr, Y, Zr, Ba, La, Ce) were identified. Elements with potential negative effects on biota such as Cu, Zn, and Cr were also highlighted. Furthermore, the composition of the total of NPs (excluding families) is compared with elemental ratios from materials of different origins (volcanic, detrital, atmospheric) to validate their volcanic source.

Nanozymes and Their Potential Roles in the Origin of Life

The origin of life has long been a central scientific challenge, with various hypotheses proposed. The chemical evolution, which supposes that inorganic molecules can transform into organic molecules and subsequent primitive cells, laid the foundation for modern theories. Inorganic minerals are believed to play crucial catalytic roles in the process. However, the harsh reaction conditions of inorganic minerals hinder the accumulation of organic molecules, preventing the efficient transition from inorganic molecules to biomacromolecules. Given the inherent physicochemical properties and enzyme-like activities, this study proposes that nanozymes, nanomaterials with enzyme-like activities, act as efficient prebiotic catalysts in the origin of life. This hypothesis is based on the following: First, unlike traditional minerals, nanominerals can catalyze organic synthesis under milder conditions. Second, nanominerals can not only protect biomolecules from radiation damage but also catalyze polymerization reactions to form functional biomacromolecules and further lipid vesicles. More importantly, nanominerals are abundant in terrestrial and extraterrestrial environments. This perspective will systematically discuss the potential roles of nanozymes in the emergence of life based on the functions of minerals and the characteristics of nanozymes. We hope the research on nanozymes and the origin of life will bridge the gap between inorganic precursors and biomolecules under primitive environments.

Incidental iron oxide nanoclusters drive confined Fenton-like detoxification of solid wastes towards sustainable resource recovery

The unique properties of nanomaterials offer vast opportunities to advance sustainable processes. Incidental nanoparticles (INPs) represent a significant part of nanomaterials, yet their potential for sustainable applications remains largely untapped. Herein, we developed a simple strategy to harness INPs to upgrade the waste-to-resource paradigm, significantly reducing the energy consumption and greenhouse gas emissions. Using the recycling of fly ash from municipal solid waste incineration (MSWI) as a proof of concept, we reveal that incidental iron oxide nanoclusters confined inside the residual carbon trigger Fenton-like catalysis by contacting H2O2 at circumneutral pH (5.0-7.0). This approach efficiently detoxifies the adsorbed dioxins under ambient conditions, which otherwise relies on energy-intensive thermal methods in the developed recovery paradigms. Collective evidence underlines that the uniform distribution of iron oxide nanoclusters within dioxin-enriched nanopores enhances the collision between the generated active oxidants and dioxins, resulting in a substantially higher detoxification efficiency than the Fe(II)-induced bulk Fenton reaction. Efficient and cost-effective detoxification of MSWI fly ash at 278‒288 K at pilot scale, combined with the satisfactory removal of adsorbed chemicals in other solid wastes unlocks the great potential of incidental nanoparticles in upgrading the process of solid waste utilization and other sustainable applications.

Extreme heat event influences the toxic impacts of nano-TiO2 with different crystal structures in mussel Mytilus coruscus

The wide use of nano‑titanium dioxide (nano-TiO2) and its ubiquitous emission into aquatic environments are threatening environmental health. Ambient temperature can affect the aggregation state of nano-TiO2 in seawater, thus influencing the intake and physiological effects on marine species. We studied the physiological effects of mixed nano-TiO2 (a mixture of anatase and rutile crystals with an average particle size of 25 nm, P25) on mussels. Subsequently, we investigated the oxidative stress, immunotoxicity, neurotoxicity, and detoxification in Mytilus coruscus exposed to two different crystal structures of nano-TiO2 (anatase and rutile) at 100 μg/L concentration under marine heatwaves (MHWs, 28 °C). MHWs and nano-TiO2 exposure induced neurotoxicity and immune damage and caused dysregulation of redox balance in the gills. Moreover, MHWs exposure disturbed the glutathione system and detoxification function of mussels, resulting in enhanced toxicity of nano-TiO2 under co-exposure. Anatase exposure significantly impaired the antioxidant system and downregulated the relative expression of antioxidant-related genes (Nrf2 and Bcl-2), HSP-90, and immune parameters under MHWs, while producing higher ROS levels compared to rutile. Based on integrated biomarker response (IBR), mussels co-exposed to anatase and MHW showed the highest value (19.29). However, there was no significant difference in bioaccumulation of titanium between anatase (6.07 ± 0.47 μg/g) and rutile (5.3 ± 0.44 μg/g) exposures under MHWs. These results indicate that MHWs would elevate the potential hazard of nanoparticles to marine organisms.

Synergistic promotion mechanism and structure-function relationship of nonmetallic atoms doped carbon nanodots driving Tagetes patula L. to remediate cadmium-contaminated soils

Phytoremediation is an economical and effective strategy to remove cadmium (Cd) from polluted environments. To improve its efficiency, nanotechnology has been proposed to collaborate with hyperaccumulators in the remediation of Cd-polluted soils. However, the intricate structure-function relationship and the underlying regulatory mechanisms by which nanomaterials regulate Cd migration and conversion within the soil-plant system remained unrevealed. In this study, functional carbon nanodots (FCNs) were modified by doping with nitrogen and (or) sulfur elements. The synthesized nonmetallic atoms-doped FCNs were utilized to investigate their structure-function relationship and the regulatory mechanisms underlying their role in the phytoremediation of Cd-polluted soils by Tagetes patula L. FCNs-based nanomaterials can regulate the migration and bioaccumulation of Cd in the soil-plant system, which exhibits an obvious structural dependency. Specifically, the synergistic application of sulfur doped FCNs and Tagetes patula L. had the highest Cd removal efficiency of 53.2 %, which was 20.1 % higher than Tagetes patula L. alone. The uptake and migration of Cd in the soil-plant system are regulated by FCNs-based nanomaterials through both direct and indirect mechanisms, involving interfacial reactions, plant physiology regulation and environmental influence. This study not only sheds light on the fate of FCNs-based nanomaterials and Cd in the soil-plant system, but also provides innovative nanotools for reinforcing phytoremediation efficiency in contaminated soils.

Nanocolloids in the soil environment: Transformation, transport and ecological effects

Nanocolloids (Ncs) are ubiquitous in natural systems and play a critical role in the biogeochemical cycling of trace metals and the mobility of organic pollutants. However, the environmental behavior and ecological effects of Ncs in the soil remain largely unknown. The accumulation of Ncs may have detrimental or beneficial effects on different compartments of the soil environment. This review discusses the major transformation processes (e.g., agglomeration/aggregation, absorption, deposition, dissolution, and redox reactions), transport, bioavailability of Ncs, and their roles in element cycles in soil systems. Notably, Ncs can act as effective carriers for other pollutants and contribute to environmental pollution by spreading pathogens, nutrients, heavy metals, and organic contaminants to adjacent water bodies or groundwater. Finally, the key knowledge gaps are highlighted to better predict their potential risks, and important new directions include exploring the geochemical process and mechanism of Ncs's formation; elucidating the transformation, transport, and ultimate fate of Ncs, and their long-term effect on contaminants, organisms, and elemental cycling; and identifying the impact on the growth and quality of important crops, evaluating its dominant effect on agro-ecosystems in the soil environment.

Mode of application of sulfonated graphene modulated bioavailable heavy metal contents and microbial community composition in long-term heavy metal contaminated soil

Nanomaterials are increasingly recognized for their potential in soil remediation. However, their impact on soil microbial communities in contaminated soil remains poorly understood. In this study, we investigated the dynamic effects of sulfonated graphene (SG) following one-time or repeated applications on heavy metal availability and soil microbial communities in long-term heavy metal-contaminated soil over 180 days. Our findings revealed that one-time SG application at 30 mg kg-1 significantly increased the bioavailable cadmium (Cd) and copper (Cu) contents by approximately 30 %-40 % after 2 and 180 days. Repeated SG applications, however, displayed no significant influence on heavy metal availability. One-time SG application, coupled with the increased available Cd, induced significant enrichment of some specific functional bacterial genera involved in glycan biosynthesis metabolism and biosynthesis of other secondary metabolites, thereby decreasing the available contents of heavy metals after 90 days. However, the shifts in bacterial community structure and function were subsequently partially recovered after 180 days. Conversely, repeated SG treatments led to minimal alterations after 90 days while leading to similar shifts in the bacterial community at 60 mg kg-1 after 180 days. The fungal community structure remained largely unaltered across all SG treatments. Intriguingly, SG treatments substantially stimulated fungal biomass, with the stimulation degree dependent on SG dosage. These results provide valuable insights for developing phytoremediation strategies, suggesting tailored SG applications during specific growth phases to optimize remediation efficiency.

Antibacterial Capabilities of Metallic Nanoparticles and Influencing Factors

The increase of antibiotic resistance in bacteria has become a major concern for successful diagnosis and treatment of infectious diseases. Over the past few decades, significant progress has been achieved on the development of nanotechnology‐based medicines for combating multidrug resistance in microorganisms. Among these, metallic nanoparticles (MNPs) hold great promise in addressing this challenge due to their broad‐spectrum and robust antimicrobial properties. This review illustrates the antibacterial activities of MNPs and further elucidates how different factors including synthesis method, size, shape, surface charge, pH, dose, type of capping or stabilizing agents of MNPs, and Gram‐type of the bacteria, impact their antibacterial activities, which are expected to promote the future development of more potent MNP‐based antibacterial agents.

Functional carbon nanodots enhance tomato tolerance to zinc deficient soils: Mechanisms and structure-function relationships

Zinc (Zn) deficiency is a global problem disorder affecting both crops and humans. Herein, modified functional carbon nanodots (MFCNs) with various structures and characteristics were developed to regulate tomato yields and Zn migration in plant-soil systems affected by Zn deficiency through structure-function relationships. Sulfur-doped FCNs (S-FCNs), nitrogen-doped FCNs (N-FCNs), and nitrogen‑sulfur co-doped FCNs (N,S-FCNs) were hydrothermally modified using FCNs as precursors. Their regulatory effects on tomatoes growing in Zn-deficient alkaline soils were studied in pot culture experiments. Specifically, 8 mg kg-1 of FCNs and S-FCNs improved tomato yields by 132 % and 108 %, respectively, compared with the control. However, N-FCNs and N,S-FCNs showed no significant effect on yield compared with the control (P < 0.05). Moreover, the application of FCNs or S-FCNs significantly improved fruit quality and nutritional value, including Zn content (by 26.3 % and 22.0 %, respectively) and naturally occurring antioxidants (by 3.37- and 2.08-fold for lycopene, 1.31- and 1.18-fold for flavonoids, and 2.28- and 1.89-fold for phenolics, respectively; P < 0.05). Although N-FCNs and N,S-FCNs increased Zn contents, they inhibited the synthesis of naturally occurring antioxidants in fruits. Zn bioaccessibility, uptake, and transportation in plant-soil systems were regulated by MFCNs through both direct and indirect mechanisms, including ionic reactions, plant physiology, and environmental effects. MFCNs regulated plant tolerance to Zn deficiency not only by affecting root activity, redox homeostasis, micronutrient balance, chelator synthesis, genetic expression, and plant photosynthesis but also by influencing rhizosphere soil properties and the microbial environment. Based on their dual role as "plant growth regulators" and "soil conditioners", MFCNs may have general applicability in agriculture. This study highlights the behavior of MFCNs in plant-soil systems, providing innovative nanotools for enhancing Zn availability, crop stress resistance and environmental preservation in sustainable agriculture.

Evolution of Heterogeneous Tunnel Structures in Cryptomelane-Type Manganese Oxides and Their Geoinspired Implications

Cryptomelane-type manganese oxides, α-MnO2 (KxMn8O16), play key roles in various fields such as geochemical processes, catalytic reactions, energy storage, and environmental sciences. The function of cryptomelane-type oxides can be affected by cation substitutions and the changes in tunnel structures. Research on natural cryptomelane minerals could provide geoinspiration for the design of new nanomaterials with cation substitutions, as well as a key to understanding the evolution of tunnel structures. In this study, natural cryptomelane minerals are characterized by the cosubstitution of iron and zinc. The localization of cosubstituted Fe and Zn in the tunnel framework has been revealed. Furthermore, the evolution of heterogeneous tunnel structures in cryptomelane has been demonstrated as a transition from large-size tunnels to small ones with high Mn(III) concentrations, indicating the significant role of Mn(III) in driving this transition. Lead (Pb2+) can be effectively trapped in the 2 × 2 tunnels. A mechanism for the attachment of cryptomelane crystals in different orientations has also been explored, showing that the migration of Mn atoms and the formation of (110) planes at specific sites contribute to lattice matching at the boundary. Our results provide geoinspired insights into controlled synthesis with Fe/Zn cosubstitution, a fundamental understanding of the evolution of tunnel structures, and functionalized applications of tunnel-based nanomaterials.

Joint Toxicity and Interaction of Carbon-Based Nanomaterials with Co-Existing Pollutants in Aquatic Environments: A Review

This review paper focuses on the joint toxicity and interaction of carbon-based nanomaterials (CNMs) with co-existing pollutants in aquatic environments. It explores the potential harmful effects of chemical mixtures with CNMs on aquatic organisms, emphasizing the importance of scientific modeling to predict mixed toxic effects. The study involved a systematic literature review to gather information on the joint toxicity and interaction between CNMs and various co-contaminants in aquatic settings. A total of 53 publications were chosen and analyzed, categorizing the studies based on the tested CNMs, types of co-contaminants, and the used species. Common test models included fish and microalgae, with zebrafish being the most studied species. The review underscores the necessity of conducting mixture toxicity testing to assess whether the combined effects of CNMs and co-existing pollutants are additive, synergistic, or antagonistic. The development of in silico models based on the solid foundation of research data represents the best opportunity for joint toxicity prediction, eliminating the need for a great quantity of experimental studies.

Abiotic and biotic-controlled nanomaterial formation pathways within the Earth's nanomaterial cycle

Nanomaterials have unique properties and play critical roles in the budget, cycling, and chemical processing of elements on Earth. An understanding of the cycling of nanomaterials can be greatly improved if the pathways of their formation are clearly recognized and understood. Here, we show that nanomaterial formation pathways mediated by aqueous fluids can be grouped into four major categories, abiotic and biotic processes coupled and decoupled from weathering processes. These can be subdivided in 18 subcategories relevant to the critical zone, and environments such as ocean hydrothermal vents and the upper mantle. Similarly, pathways in the gas phase such as volcanic fumaroles, wildfires and particle formation in the stratosphere and troposphere can be grouped into two major groups and five subcategories. In the most fundamental sense, both aqueous-fluid and gaseous pathways provide an understanding of the formation of all minerals which are inherently based on nanoscale precursors and reactions.

Phytotoxicity of Prussian blue nanoparticles to rice and the related defence mechanisms: In vivo observations and physiological and biochemical analysis

While the nanotoxic effects on plants have been extensively studied, the underlying mechanisms of plant defense responses and resistance to nanostress remain insufficiently understood. Particularly, Prussian blue nanoparticles (PB NPs) have been extensively used in pigments, pharmaceuticals, electrocatalysis, biosensors and energy storage. However, the impact of PB NPs on plants' health and growth are largely unknown. Herein, the phytotoxicity of PB NPs to rice and trace the uptake, accumulation and biotransformation of PB NPs was explored, along with the underlying defence mechanisms. The results showed that PB NPs (≥50 mg L-1) significantly inhibited the growth of rice seedling up to 16.16%, 27.80%, and 29.37% in plant height, shoot biomass and root biomass, respectively. The X-ray spectroscopic studies and in vivo elemental and particle-imaging demonstrated that PB NPs were transported through the cortex via xylem from root to shoot. However, most of the PB NPs and their transformation products were retained in the root, where they were blocked owing to root cell wall (RCW) remodeling, and 81.4%-83.4% of Fe accumulated in the RCW compared to 66.6% in the control. Specifically, PB NPs stimulated pectin methylesterase activity by promoting hydrogen peroxide production to participate in RCW remodeling. More interestingly, Si was specifically regulated to covalently bind to hemicellulose to form the Si-hemicellulose complex that strongly bound with PB NPs during RCW remodeling, resulting in the strong defense against PB NPs. These findings provide new insights into the phytotoxicity of artificial NPs and the defense mechanisms of plants.

Silver nanoparticles regulate antibiotic resistance genes by shifting bacterial community and generating anti-silver genes in estuarine biofilms

Biofilms are thought to be sinks for antibiotic resistance genes (ARGs) and nanoparticles (NPs), however, studies on the interactions between NPs and ARGs in biofilms are limited. This study focused on the occurrence and regulatory mechanisms of ARGs during the formation of biofilms with continuous treatment of zero-valent silver nanoparticles (Ag0-NPs) and Ag ions at an environmental concentration of 10 µg/L in the Yangtze Estuary. The biofilms could enrich large amounts of Ag, with the highest concentration of 97.60 mg/kg and 111.08 mg/kg in the Ag0-NPs and Ag ions group at 28 days. Compared to the blank at 28 days, the abundance of ARGs was reduced 2.2 times in the Ag0-NPs group, whereas it increased 1.3 times in the Ag ion group. Ag0-NPs and Ag ions induced the production of silver resistance genes (SRGs) or selected bacteria with SRGs in biofilms. Based on machine learning, the bacterial community, SRGs, and Ag concentration were the top three dominant regulators of ARGs, with 27.74 %, 25.57 %, and 17.93 % contributions, respectively. Structural equation modeling revealed that Ag could indirectly regulate ARGs by regulating the bacterial community in the Ag0-NPs group. Metagenomic sequencing further showed that most of the decreased ARGs were hosted by Betaproteobacteria in the Ag0-NPs groups. According to the KEGG pathway database, the possible molecular mechanism of Ag0-NPs/Ag ions regulating ARGs may be through the two-component system (arlS/silS-arlR) and beta-lactam resistance system (mexI-mexV-oprM/oprZ/smeF). Overall, this study provides new insights into the effects of Ag0-NPs at environmental concentrations on the ecological environment, especially regarding the mechanism of regulating ARGs in estuarine biofilms.

Molecular mechanisms of iron nanominerals formation in fungal extracellular polymeric substances (EPS) layers during fungus-mineral interactions

Extracellular polymeric substances (EPS), which envelop on fungal hyphae surface, interact strongly with minerals and play a crucial role in the formation of nanoscale minerals during biomineralization in nature environments. However, it remains poorly understood about the molecular mechanisms of nanominerals (i.e., iron nanominerals) formation in fungal EPS halos during fungus-mineral interactions. This process is vital because fungi typically grow attached to various mineral surfaces in nature. According to the changes of thickness of the fungal cell and EPS layers during the Trichoderma guizhouense NJAU 4742 and hematite cultivation experiments, we found that fungal biomineralization could trigger the formation of EPS layers. Fe-dominated nanominerals, aromatic C (283-286.1 eV), alkyl C (287.6-288.3 eV), and carboxylic C (288.4-289.1 eV) were the dominant chemical groups on the EPS layers, as determined by nanoscale secondary ion mass spectrometry (NanoSIMS), high-resolution transmission electron microscope (HRTEM), and carbon 1s near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Further, evidence from Fe K-edge X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) spectra indicated that oxygen vacancy (OV) was formed on the Fe-dominated nanomineral surface during fungus-mineral interactions, which played an important role in catalyzing H2O2 decomposition and HO∗ production. Taken together, the intrinsic peroxidase-like activity by reactive oxygen species (ROS) could modulate the Fe-dominated nanominerals formation in EPS layers to newly form a physical barrier between the cell and the external environments around hyphae, providing novel insights into the effects of ROS-mediated fungal-mineral interactions on fungal nutrient recycling, attenuation of contaminants, and biological control in nature environments.

Simultaneous Reduction and Methylation of Nanoparticulate Mercury: The Critical Role of Extracellular Electron Transfer

Mercury nanoparticles are abundant in natural environments. Yet, understanding their contribution to global biogeochemical cycling of mercury remains elusive. Here, we show that microbial transformation of nanoparticulate divalent mercury can be an important source of elemental and methylmercury.Geobacter sulfurreducensPCA, a model bacterium predominant in anoxic environments (e.g., paddy soils), simultaneously reduces and methylates nanoparticulate Hg(II). Moreover, the relative prevalence of these two competing processes and the dominant transformation pathways differ markedly between nanoparticulate Hg(II) and its dissolved and bulk-sized counterparts. Notably, even when intracellular reduction of Hg(II) nanoparticles is constrained by cross-membrane transport (a rate-limiting step that also regulates methylation), the overall Hg(0) formation remains substantial due to extracellular electron transfer. With multiple lines of evidence based on microscopic and electrochemical analyses, gene knockout experiments, and theoretical calculations, we show that nanoparticulate Hg(II) is preferentially associated with c-type cytochromes on cell membranes and has a higher propensity for accepting electrons from the heme groups than adsorbed ionic Hg(II), which explains the surprisingly larger extent of reduction of nanoparticles than dissolved Hg(II) at relatively high mercury loadings. These findings have important implications for the assessment of global mercury budgets as well as the bioavailability of nanominerals and mineral nanoparticles.

Analytical solution of a microrobot-blood vessel interaction model

This study develops a dynamics model of a microrobot vibrating in a blood vessel aiming to detect potential cancer metastasis. We derive an analytical solution for microrobot's motion, considering interactions with the vessel walls modelled by a linear spring-dashpot and a constant damping value for blood viscosity. The model facilitates instantaneous state transitions of the microrobot, such as contact with the vessel wall and free motion within the fluid. Amplitudes and phase angles from the transient solutions of dynamics model of the microrobot are solved at arbitrary moments, providing insights into its transient dynamics. The analytical solution of the proposed system is validated by experimental data, serving as a benchmark to examine the influence of pertinent parameters on microrobot's dynamic response. It is found that the contact force transmitted to the vessel wall, assessed by system's transmissibility function dependent on damping and frequency ratios, decreases with increasing damping ratio and intensifies when the frequency ratio is below 2 . At the frequency ratio is equal to 1, resonance phenomenon is dominated by the magnification factor linked to the damping ratio, increasing the amplitude of resonance as damping decreases. Finally, different sets of system parameters, including excitation frequency and magnitude, fluid damping, vessel wall's stiffness and damping, reveal multi-periodic motions and fake collision of the microrobot with the vessel wall. Simulation results imply that these phenomena are minimally affected by vessel wall's stiffness but are significantly influenced by other parameters, such as fluid damping coefficient and damping coefficient of the blood vessel wall. This research provides a robust theoretical foundation for developing control strategies for microrobots aimed at detecting cancer metastasis.

Size and isotope analysis of individual nanoparticles by multi-collector ICP-MS using "event-triggered signal capture" with a high-speed oscilloscope

Accurate quantitative elemental and isotope analysis of nanoparticles at the single-particle level is crucial for better understanding their origin, properties and behaviors. Single particle inductively coupled plasma-mass spectrometry (spICP-MS) has emerged as a promising technique for nanoparticle analysis. However, challenges persist in obtaining accurate and consistent element profiles and ratios for small-sized nanoparticles by conventional quadrupole (QMS) or time-of-flight mass analyzers (TOF-MS) due to their low level and transient nature. In this paper, we present a novel analytical method for single nanoparticle analysis using multiple collector ICP-MS (MC-ICP-MS) combined with a modern high-speed digital oscilloscope. The single particle events are acquired using an "event-triggered signal capture" (ETSC) technique, which enables the simultaneously capture and visualization of multiple isotopes of transient individual particle profiles with nanosecond time resolution. This greatly facilitates precise and efficient analysis of nanoparticles. The minimum detectable particle size is calculated to be as small as 8 nm (∼1 ag 109Ag) for AgNPs. Based on the 109/107Ag ratios obtained from 2000 particles, the precisions of 109/107Ag ratio measurements on 20 nm, 40 nm, 60 nm, 80 nm and 100 nm were approximately 0.086 (SD), 0.063 (SD), 0.051 (SD), 0.040 (SD), and 0.029 (SD), which is limited by counting statistics of the isotopic signals. Furthermore, the achieved standard error of 109/107Ag can be reduced to sub-permil level (0.7 ‰) even for the measurement of 20 nm AgNPs (N = 17,000). These results demonstrate that the ETSC provides a unique method for isotope analysis of single particles, holding great potential for enhancing our understanding of nanoparticles.

Harnessing RNA interference for the control of Fusarium species: A critical review

Fusarium fungi are a pervasive threat to global agricultural productivity. They cause a spectrum of plant diseases that result in significant yield losses and threaten food safety by producing mycotoxins that are harmful to human and animal health. In recent years, the exploitation of the RNA interference (RNAi) mechanism has emerged as a promising avenue for the control of Fusarium-induced diseases, providing both a mechanistic understanding of Fusarium gene function and a potential strategy for environmentally sustainable disease management. However, despite significant progress in elucidating the presence and function of the RNAi pathway in different Fusarium species, a comprehensive understanding of its individual protein components and underlying silencing mechanisms remains elusive. Accordingly, while a considerable number of RNAi-based approaches to Fusarium control have been developed and many reports of RNAi applications in Fusarium control under laboratory conditions have been published, the applicability of this knowledge in agronomic settings remains an open question, and few convincing data on RNAi-based disease control under field conditions have been published. This review aims to consolidate the current knowledge on the role of RNAi in Fusarium disease control by evaluating current research and highlighting important avenues for future investigation.

Protein Corona Formation on Cadmium-Bearing Nanoparticles: Important Role of Facet-Dependent Binding of Cysteine-Rich Proteins

Cadmium-bearing nanoparticles, such as nanoparticulate cadmium selenide (CdSe) and cadmium sulfide (CdS), widely exist in the environment and originate from both natural and anthropogenic sources. Risk assessment of these nanoparticles cannot be accurate without taking into account the properties of the protein corona that is acquired by the nanoparticles upon biouptake. Here, we show that the compositions of the protein corona on CdSe/CdS nanoparticles are regulated collectively by the surface atomic arrangement of the nanoparticles and the abundance and distribution of cysteine moieties of the proteins in contact with the nanoparticles. A proteomic analysis shows that the observed facet-dependent preferential binding of proteins is mostly related to the cysteine contents of the proteins, among commonly recognized protein properties controlling the formation of the protein corona. Theoretical calculations further demonstrate that the atomic arrangement of surface Cd atoms, as dictated by the exposed facets of the nanoparticles, controls the specific binding mode of the S atoms in the disulfide bonds of the proteins. Supplemental protein adsorption experiments confirm that disulfide bonds remain intact during protein adsorption, making the binding of protein molecules sensitive to the abundance and distribution of Cd-binding moieties and possibly molecular rigidity of the proteins. The significant conformational changes of adsorbed proteins evidenced from a circular dichroism spectroscopy analysis suggest that disrupting the structural stability of proteins may be an additional risk factor of Cd-bearing nanoparticles. These findings underline that the unique properties and behaviors of nanoparticles must be fully considered when evaluating the biological effects and health risks of metal pollutants.

From Bulk to Nano: Formation, Features, and Functions of Nano-Black Carbon in Biogeochemical Processes

Globally increasing wildfires and widespread applications of biochar have led to a growing amount of black carbon (BC) entering terrestrial ecosystems. The significance of BC in carbon sequestration, environmental remediation, and the agricultural industry has long been recognized. However, the formation, features, and environmental functions of nanosized BC, which is one of the most active fractions in the BC continuum during global climate change, are poorly understood. This review highlights the formation, surface reactivity (sorption, redox, and heteroaggregation), biotic, and abiotic transformations of nano-BC, and its major differences compared to other fractions of BC and engineered carbon nanomaterials. Potential applications of nano-BC including suspending agent, soil amendment, and nanofertilizer are elucidated based on its unique properties and functions. Future studies are suggested to develop more reliable detection techniques to provide multidimensional information on nano-BC in environmental samples, explore the critical role of nano-BC in promoting soil and planetary health from a one health perspective, and extend the multifield applications of nano-BC with a lower environmental footprint but higher efficiency.

Metal-containing nanoparticles in road dust from a Chinese megacity over the last decade: Spatiotemporal variation and driving factors

As a crucial sink of metal-containing nanoparticles (MNPs), road dust can record their spatiotemporal variations in urban environments. In this study, taking Shanghai as a representative megacity in China, a total of 272 dust samples were collected in the winter and summer of 2013 and 2021/2022 to understand the spatiotemporal variations and driving factors of MNPs. The number concentrations of Fe-, Ti-, and Zn-containing NPs were 3.8 × 106 - 8.4 × 108, 2.3 × 106-1.4 × 108, and 6.0 × 105-2.3 × 108 particles/mg, respectively, according to single particle (sp)ICP-MS analysis. These MNPs showed significantly higher number concentrations in summer than in winter. Hotspots of Fe-containing NPs were more concentrated in industrial and traffic areas, Zn-containing NPs were mainly distributed in the central urban areas, while Ti-containing NPs were abundant in areas receiving high rainfall. The structural equation model results indicates that substantial rainfall in summer can help remove MNPs from atmospheric PM2.5 into dust, while in winter industrial and traffic activities were the primary contributors for MNPs. Moreover, the contribution of traffic emissions to MNPs has surpassed industrial one over the last decade, highlighting the urgency to control traffic-sourced MNPs, especially those from non-exhaust emissions by electric vehicles.

Location-dependent occurrence and distribution of metal-based nanoparticles in bay environments

Metal-based nanoparticles (MNPs) are increasingly being released into the marine environment, posing potential environmental risks. However, factors governing the environmental occurrence and distribution of MNPs in bays still lack a comprehensive understanding. Herein, we collected seawater and sediment samples from two adjacent bays (Daya Bay and Honghai Bay, which have similar water qualities), and determined the particle concentrations and sizes of multi-element MNPs (Ti-, Cu-, Zn-, Ag-, Mn-, Pb- and Cr-based NPs) via single particle inductively coupled plasma-mass spectrometry (spICP-MS). The internal circulation in Daya Bay has resulted in an even distribution of MNPs' particle concentrations and sizes in both seawater and sediments, while the terrestrial discharge in Honghai Bay has led to a gradient-decreasing trend in MNPs' concentrations from nearshore to offshore. Moreover, the relatively high abundance of MNPs in Honghai Bay has contributed to 2.35-fold higher environmental risks than Daya Bay. Overall, this study has provided solid evidence on the critical but overlooked factors that have shaped the occurrence and distribution of MNPs, providing new insights for risk management and emission regulation.

Tracking fine particles in urban and rural environments using honey bees as biosamplers in Mexico

This work explores the efficiency of honey bees (Apis mellifera) as biosamplers of metal pollution. To understand this, we selected two cities with different urbanization (a medium-sized city and a megacity), and we collected urban dust and honey bees captured during flight. We sampled two villages and a university campus as control areas. The metal content in dust was analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Atomic Force Microscopy (AFM) and Scanning electron microscopy (SEM) were used to investigate the shape and size distribution of the particles, and to characterize the semiquantitative chemical composition of particles adhered to honey bee's wings. Principal Component Analysis (PCA) shows a distinctive urban dust geochemical signature for each city, with component 1 defining V-Cr-Ni-Tl-Pt-Pb-Sb as characteristic of Mexico City and Ce-As-Zr for dust from Hermosillo. Particle count using SEM indicates that 69% and 63.4% of the resuspended dust from Hermosillo and Mexico City, respectively, corresponds to PM2.5. Instead, the particle count measured on the honey bee wings from Hermosillo and Mexico City is mainly PM2.5, 91.4% and 88.9%, respectively. The wings from honey bees collected in the villages and the university campus show much lower particle amounts. AFM-histograms confirmed that the particles identified in Mexico City have even smaller sizes (between 60 and 480 nm) than those in Hermosillo (between 400 and 1400 nm). Particles enriched in As, Zr, and Ce mixed with geogenic elements such as Si, Ca, Mg, K, and Na dominate honey bee' wings collected in Hermosillo. In contrast, those particles collected from Mexico City contain V, Cr, Ni, Tl, Pt, Pb, and Sb. Such results agree with the urban dust data. This work shows that honey bees are suitable biosamplers for the characterization of fine dust fractions by microscopy techniques and reflect the urban pollution of the sites.

Repeated marine heatwaves aggravate the adverse effects of nano-TiO2 on physiological metabolism of the thick-shelled mussel Mytilus coruscus

Global climate change is a major trigger of unexpected temperature fluctuations. The impacts of marine heatwaves (MHWs) and nano-titanium dioxide (nano-TiO2) on marine organisms have been extensively investigated. However, the potential mechanisms underlying their interactive effects on physiological processes and metabolism remain poorly understood, especially regarding periodic MHWs in real-world conditions. In this study, the effects of nano-TiO2 (at concentrations of 0, 25, and 250 μg/L) and periodic MHWs on the condition index (CI) and underlying metabolic mechanisms were investigated in mussels (Mytilus coruscus). The results showed that mussels try to upregulate their respiration rate (RR) to enhance aerobic metabolism (indicated by elevated succinate dehydrogenase) under short-term nano-TiO2 exposure. However, even at ambient concentration (25 μg/L), prolonged nano-TiO2 exposure inhibited ingestion ability (decreased clearance rate) and glycolysis (inhibited pyruvate kinase, hexokinase, and phosphofructokinase activities), which led to an insufficient energy supply (decreased triglyceride, albumin, and ATP contents). Repeated thermal scenarios caused more severe physiological damage, demonstrating that mussels are fragile to periodic MHWs. MHWs decreased the zeta potential of the nano-TiO2 particles but increased the hydrodynamic diameter. Additionally, exposure to nano-TiO2 and periodic MHWs further affected aerobic respiration (inhibited lactate dehydrogenase and succinate dehydrogenase activities), metabolism (decreased RR, activities of respiratory metabolism-related enzymes, and expressions of PEPCK, PPARγ, and ACO), and overall health condition (decreased ATP and CI). These findings indicate that the combined stress of these two stressors exerts more detrimental impact on the physiological performance and energy metabolism of mussels, and periodic MHWs exacerbate the toxicological effects of ambient concentration nano-TiO2. Given the potential worsening of nanoparticle pollution and the increase in extreme heat events in the future, the well-being of mussels in the marine environment may face further threats.

Nanoparticle-plant interactions: Physico-chemical characteristics, application strategies, and transmission electron microscopy-based ultrastructural insights, with a focus on stereological research

Ensuring global food security is pressing among challenges like population growth, climate change, soil degradation, and diminishing resources. Meeting the rising food demand while reducing agriculture's environmental impact requires innovative solutions. Nanotechnology, with its potential to revolutionize agriculture, offers novel approaches to these challenges. However, potential risks and regulatory aspects of nanoparticle (NP) utilization in agriculture must be considered to maximize their benefits for human health and the environment. Understanding NP-plant cell interactions is crucial for assessing risks of NP exposure and developing strategies to control NP uptake by treated plants. Insights into NP uptake mechanisms, distribution patterns, subcellular accumulation, and induced alterations in cellular architecture can be effectively drawn using transmission electron microscopy (TEM). TEM allows direct visualization of NPs within plant tissues/cells and their influence on organelles and subcellular structures at high resolution. Moreover, integrating TEM with stereological principles, which has not been previously utilized in NP-plant cell interaction assessments, provides a novel and quantitative framework to assess these interactions. Design-based stereology enhances TEM capability by enabling precise and unbiased quantification of three-dimensional structures from two-dimensional images. This combined approach offers comprehensive data on NP distribution, accumulation, and effects on cellular morphology, providing deeper insights into NP impact on plant physiology and health. This report highlights the efficient use of TEM, enhanced by stereology, in investigating diverse NP-plant tissue/cell interactions. This methodology facilitates detailed visualization of NPs and offers robust quantitative analysis, advancing our understanding of NP behavior in plant systems and their potential implications for agricultural sustainability.

Potassium permanganate-modified eggshell biosorbent for the removal of diclofenac from liquid environment: adsorption performance, isotherm, kinetic, and thermodynamic analyses

This study assess how well diclofenac (DCF) can be separated from aqueous solution using potassium permanganate-modified eggshell biosorbent (MEB). The MEB produced was characterised using XRD, FTIR, and SEM. Batch experiments were conducted to examine and assess the impact of contact time, adsorbent dosage, initial concentration, and temperature on the adsorption capacity of the MEB in the DCF sequestration. The best parameters to obtained 95.64% DCF removal from liquid environment were 0.05 g MEB weight, 50 mg/L initial concentration, and 60 min contact time at room temperature. The maximum DCF sequestration capacity was found to be 159.57 mg/g with 0.05 g of MEB at 298 K. The adsorption isotherm data were more accurately predicted by the Freundlich model, indicating a process of heterogeneous multilayer adsorption. The results of the kinetic study indicated that the pseudo-second-order kinetic models best matched the experimental data. The findings revealed that the dynamic of DCF entrapment is largely chemisorption and diffusion controlled. Based on the values of thermodynamic parameters, the process is both spontaneous and endothermic. The primary processes of DCF sorption mechanism onto the MEB were chemical surface complexation, hydrogen bonding, π-π stacking, and electrostatic interactions. The produced MEB showed effective DCF separation from the aqueous solution and continued to have maximal adsorption capability even after five regeneration cycles. These findings suggest that MEB could be highly efficient adsorbent for the removal of DCF from pharmaceutical wastewater.

Nanotechnology for the enhancement of algal cultivation and bioprocessing: Bridging gaps and unlocking potential

Algae cultivation and bioprocessing are important due to algae's potential to effectively tackle crucial environmental challenges like climate change, soil and water pollution, energy security, and food scarcity. To realize these benefits high algal biomass production and valuable compound extraction are necessary. Nanotechnology can significantly improve algal cultivation through enhanced nutrient uptake, catalysis, CO2 utilization, real-time monitoring, cost-effective harvesting, etc. Synthetic nanoparticles are extensively used due to ease of manufacturing and targeted application. Nonetheless, there is a growing interest in transitioning to environmentally friendly options like natural and 'green' nanoparticles which are produced from renewable/biological sources by using eco-friendly solvents. Presently, natural, and 'green' nanoparticles are predominantly utilized in algal harvesting, with limited application in other areas, the reasons for which remain unclear. This review aims to critically evaluate research on nanotechnology-based algae system enhancement, identify research gaps and propose solutions using natural and 'green' nanoparticles for a sustainable future.

Bacterial Susceptibility to Ceria Nanoparticles: The Critical Role of Surrounding Molecules

Investigating the ternary relationship among nanoparticles (NPs), their immediate molecular environment, and test organisms rather than the direct interaction between pristine NPs and test organisms has been thrust into the mainstream of nanotoxicological research. Diverging from previous work that predominantly centered on surrounding molecules affecting the toxicity of NPs by modulating their nanoproperties, this study has unveiled a novel dimension: surrounding molecules altering bacterial susceptibility to NPs, consequently impacting the outcomes of nanobio interaction. The study found that adding nitrate as the surrounding molecules could alter bacterial respiratory pathways, resulting in an enhanced reduction of ceria NPs (nanoceria) on the bacterial surfaces. This, in turn, increased the ion-specific toxicity originating from the release of Ce3+ ions at the nanobio interface. Further transcriptome analysis revealed more mechanistic details underlying the nitrate-induced changes in the bacterial energy metabolism and subsequent toxicity patterns. These findings offer a new perspective for the deconstruction of nanobio interactions and contribute to a more comprehensive understanding of NPs' environmental fate and ecotoxicity.

Validation of a Method for Surveillance of Nanoparticles in Mussels Using Single-Particle Inductively Coupled Plasma-Mass Spectrometry

BACKGROUND

Determining the concentration of nanoparticles (NPs) in marine organisms is important for evaluating their environmental impact and to assess potential food safety risks to human health.

OBJECTIVE

The current work aimed at developing an in-house method based on single-particle inductively coupled plasma-mass spectrometry (SP-ICP-MS) suitable for surveillance of NPs in mussels.

METHODS

A new low-cost and simple protease mixture was utilized for sample digestion, and novel open-source data processing was used, establishing detection limits on a statistical basis using false-positive and false-negative probabilities. The method was validated for 30 and 60 nm gold NPs spiked to mussels as a proxy for seafood.

RESULTS

Recoveries were 76-77% for particle mass concentration and 94-101% for particle number concentration. Intermediate precision was 8-9% for particle mass concentration and 7-8% for particle number concentration. The detection limit for size was 18 nm, for concentration 1.7 ng/g, and 4.2 × 105 particles/g mussel tissue.

CONCLUSION

The performance characteristics of the method were satisfactory compared with numeric Codex criteria. Further, the method was applied to titanium-, chromium- and copper-based particles in mussels.

HIGHLIGHTS

The method demonstrates a new practical and cost-effective sample treatment, and streamlined, transparent, and reproducible data treatment for the routine surveillance of NPs in mussels.

Past progress in environmental nanoanalysis and a future trajectory for atomic mass-spectrometry methods

The development of engineered nanotechnology has necessitated a commensurate maturation of nanoanalysis capabilities. Building off a legacy established by electron microscopy and light-scattering, environmental nanoanalysis has now benefited from ongoing advancements in instrumentation and data analysis, which enable a deeper understanding of nanomaterial properties, behavior, and impacts. Where once environmental nanoparticles and colloids were grouped into broad 'dissolved or particulate' classes that are dependent on a filter size cut-off, now size distributions of submicron particles can be separated and characterized providing a more comprehensive examination of the nanoscale. Inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS), directly coupled to field flow fractionation (FFF-ICP-QMS) or operated in single particle mode (spICP-MS) have spearheaded a revolution in nanoanalysis, enabling research into nanomaterial behavior in environmental and biological systems at expected release concentrations. However, the complexity of the nanoparticle population drives a need to characterize and quantify the multi-element composition of nanoparticles, which has begun to be realized through the application of time-of-flight MS (spICP-TOFMS). Despite its relative infancy, this technique has begun to make significant strides in more fully characterizing particulate systems and expanding our understanding of nanoparticle behavior. Though there is still more work to be done with regards to improving instrumentation and data processing, it is possible we are on the cusp of a new nanoanalysis revolution, capable of broadening our understanding of the size regime between dissolved and bulk particulate compartments of the environment.