Search

Radiotherapy is an integral part of cancer therapy. Due to the low tissue specificity of radiation, damage to tumor-surrounding healthy tissue remains a major concern. Radio-enhancers based on inorganic nanomaterials have attracted considerable attention in recent years. In addition to widely exploited metal and metal oxides nanoparticles, 2D materials may offer potential advantages due to their intrinsically high specific surface area. Here, we report on the promising radio-enhancement properties of Ti3C2Tx MXenes. We show that Ti3C2Tx MXenes are readily internalized and well-tolerated by mammalian cells. In contrast to MXenes suspended in aqueous buffers which fully oxidize within days (yielding rice-grain shaped rutile nanoparticles), MXenes internalized by cells display slower oxidation rates, in line with cell-free experiments showing slower oxidation in cell media and lysosomal buffers compared to antioxidant-devoid dispersants. The MXenes show potent radio-enhancement properties with dose enhancement factors of up to 2.5 in human soft tissue sarcoma cells and no toxicity towards healthy human fibroblasts. Benchmarking against oxidized MXenes and commercial titanium dioxide nanoparticles indicates superior radio-enhancement properties of the intact 2D titanium carbide flakes. Taken together, this work provides direct evidence for the potent radio-enhancement properties of Ti3C2Tx MXenes rendering them a promising candidate material for radiotherapy enhancement.

Inorganic nanomaterials have gained increasing attention in radiation oncology, owing to their radiation therapy enhancing properties. To accelerate candidate material selection and overcome the disconnect between conventional 2D cell culture and in vivo findings, screening platforms unifying high-throughput with physiologically relevant endpoint analysis based on 3D in vitro models are promising. Here, a 3D tumor spheroid co-culture model based on cancerous and healthy human cells is presented for the concurrent assessment of radio-enhancement efficacy, toxicity, and intratissural biodistribution with full ultrastructural context of radioenhancer candidate materials. Its potential for rapid candidate materials screening is showcased based on the example of nano-sized metal–organic frameworks (nMOFs) and direct benchmarking against gold nanoparticles (the current “gold standard”). Dose enhancement factors (DEFs) ranging between 1.4 and 1.8 are measured for Hf-, Ti-, TiZr-, and Au-based materials in 3D tissues and are overall lower than in 2D cell cultures, where DEF values exceeding 2 are found. In summary, the presented co-cultured tumor spheroid—healthy fibroblast model with tissue-like characteristics may serve as high-throughput platform enabling rapid, cell line-specific endpoint analysis for therapeutic efficacy and toxicity assessment, as well as accelerated radio-enhancer candidate screening., Advanced Biology, ISSN:2701-0198

Nano-sized metal organic frameworks (nanoMOFs) have gained increasing importance in biomedicine due to their tunable properties. In addition to their use as carriers in drug delivery, nanoMOFs containing hafnium have been successfully employed as radio-enhancers augmenting damage caused by X-ray irradiation in tumor tissue. While results are encouraging, there is little mechanistic understanding available, and the biological fate of these radio-enhancer nanoparticles remains largely unexplored. Here, we synthesized a selection of group IV metal-based (Hf, Ti, Ti/Zr) nanoMOFs and investigated their cell compatibility and radio-enhancement performance in direct comparison to the corresponding metal oxides. We report surprising radio-enhancement performance of Ti-containing nanoMOFs reaching dose modifying ratios of 3.84 in human sarcoma cells and no relevant dose modification in healthy human fibroblasts. These Ti-based nanoMOFs even outperformed previously reported Hf-based nanoMOFs as well as equimolar group IV metal oxides in direct benchmarking experiments. While group IV nanoMOFs were well-tolerated by cells in the absence of irradiation, the nanoMOFs partially dissolved in lysosomal buffer conditions showing distinctly different chemical stability compared to widely researched group IV oxides (TiO2, ZrO2, and HfO2). Taken together, this study illustrates the promising potential of Ti-based nanoMOFs for radio-enhancement and provides insight into the intracellular fate and stability of group IV nanoMOFs., Biomaterials Science, 10 (22), ISSN:2047-4830, ISSN:2047-4849

Deep-tissue fluorescence imaging remains a major challenge as there is limited availability of bright biocompatible materials with high photo- and chemical stability. Contrast agents with emission wavelengths above 1000 nm are most favorable for deep tissue imaging, offering deeper penetration and less scattering than those operating at shorter wavelengths. Organic fluorophores suffer from low stability while inorganic nanomaterials (e.g. quantum dots) are based typically on heavy metals raising toxicity concerns. Here, we report scalable flame aerosol synthesis of water-dispersible Ba3(VO4)2 nanoparticles doped with Mn5+ which exhibit a narrow emission band at 1180 nm upon near-infrared excitation. Their co-synthesis with Bi2O3 results in even higher absorption and ten-fold increased emission intensity. The addition of Bi2O3 also improved both chemical stability and cytocompatibility by an order of magnitude enabling imaging deep within tissue. Taken together, these bright particles offer excellent photo-, chemical and colloidal stability in various media with cytocompatibility to HeLa cells superior to existing commercial contrast agents.

Since the start of the current COVID-19 pandemic, for the first time a significant fraction of the world's population cover their respiratory system for an extended period with mostly medical facemasks and textile masks. This new situation raises questions about the extent of mask related debris (fibers and particles) being released and inhaled and possible adverse effects on human health. This study aimed to quantify the debris release from a textile-based facemask in comparison to a surgical mask and a reference cotton textile using both liquid and air extraction. Under liquid extractions, cotton-based textiles released up to 29'452 ± 1'996 fibers g− 1 textile while synthetic textiles released up to 1'030 ± 115 fibers g− 1 textile. However, when the masks were subjected to air-based extraction scenarios, only a fraction (0.1–1.1%) of this fiber amount was released. Several metals including copper (up to 40.8 ± 0.9 µg g− 1) and iron (up to 7.0 ± 0.3 µg g− 1) were detected in acid dissolved textiles. Additionally the acute in vitro toxicity of size-fractionated liquid extracts (below and above 0.4 µm) were assessed on human alveolar basal epithelial cells. The current study shows no acute cytotoxicity response for all the analyzed facemasks.

Synchrotron hard X-ray spectroscopy with focussing optics allows recording X-ray fluorescence (XRF) maps at energies around element specific X-ray absorption edges. Stacking multiple XRF maps along the energy axis yields chemical images that contain spatially resolved information on the speciation of the absorber in the sample matrix at the micrometre scale. Short dwell times needed to keep measurement time and radiation-induced sample changes within acceptable limits result in spectral noise that affects the uncertainty in data analysis. In this study, we develop a model to quantify the uncertainty associated with the processing of XRF image stacks using Bayesian inference. To demonstrate the potential of our approach, the model is applied to stacks of XRF maps collected around the copper (Cu) K-edge (pixel size: 3 × 3 μm2, map sizes: 500 × 500 μm2). The investigated samples include digested sewage sludge spiked with either CuO nanoparticles (NP) or dissolved CuSO4 and their corresponding ashes obtained through incineration. The chemical imaging data reveal differences in species distribution between sludge spiked with CuO NP or dissolved Cu. These differences disappear during the incineration process and the resulting ashes exhibit almost identical Cu species distribution. The uncertainty analysis approach developed in this study can be used for data interpretation, but can also be used for the planning of chemical imaging experiments at synchrotron beamlines., Journal of Analytical Atomic Spectrometry, 35 (3), ISSN:0267-9477, ISSN:1364-5544

Engineered nanoparticles (NPs) that are released into wastewater are retained by wastewater treatment plants (WWTPs) and accumulate in sewage sludge. Increasing shares of sludge are incinerated and landfilled, especially in industrialized countries. It is debated whether certain types of NPs can outlive the incineration process and subsequently be released from sewage sludge ash (SSA) landfills. To investigate the release of different types of NPs from SSA, we spiked gold (Au), silver (Ag) and cerium dioxide (CeO2) NPs to a pilot WWTP increasing the Au, Ag and Ce concentrations to 30, 43 and 389 mg kg−1 (dry matter basis) in the digested sludge. The spiked sludge was incinerated in a pilot fluidized bed reactor resulting in SSA with Au, Ag and Ce concentrations of 61, 103 and 854 mg kg−1. In addition, two sludge samples from a full-scale WWTP with Au concentrations of 5 and 16 mg kg−1 were incinerated, resulting in SSA with 9 mg kg−1 and 30 mg kg−1 Au. The spiked Au-NPs remain largely unaltered during the wastewater treatment and incineration process, whereas Ag-NPs and CeO2-NPs undergo transformation. During simulated landfill leaching in columns flushed with 400 to 500 pore volumes of artificial rainwater, Ag and Ce were retained in the ash, whereas about 17% of the spiked Au was released, mainly in particulate form. Lower fractions of mostly particulate Au were released from the ashes (3 and 9%) of unspiked SSA. In conclusion, unaltered Au-NPs significantly leach from landfilled SSA, whereas the incorporation of Ag-NPs and CeO2-NPs as transformed species into the SSA matrix limits the leaching of (nano)particulate and dissolved Ag and Ce compounds. ISSN:2051-8153 ISSN:2051-8161

Engineered nanoparticles (NPs) that are released into wastewater are retained by wastewater treatment plants (WWTPs) and accumulate in sewage sludge. Increasing shares of sludge are incinerated and landfilled, especially in industrialized countries. It is debated whether certain types of NPs can outlive the incineration process and subsequently be released from sewage sludge ash (SSA) landfills. To investigate the release of different types of NPs from SSA, we spiked gold (Au), silver (Ag) and cerium dioxide (CeO2) NPs to a pilot WWTP increasing the Au, Ag and Ce concentrations to 30, 43 and 389 mg kg−1 (dry matter basis) in the digested sludge. The spiked sludge was incinerated in a pilot fluidized bed reactor resulting in SSA with Au, Ag and Ce concentrations of 61, 103 and 854 mg kg−1. In addition, two sludge samples from a full-scale WWTP with Au concentrations of 5 and 16 mg kg−1 were incinerated, resulting in SSA with 9 mg kg−1 and 30 mg kg−1 Au. The spiked Au-NPs remain largely unaltered during the wastewater treatment and incineration process, whereas Ag-NPs and CeO2-NPs undergo transformation. During simulated landfill leaching in columns flushed with 400 to 500 pore volumes of artificial rainwater, Ag and Ce were retained in the ash, whereas about 17% of the spiked Au was released, mainly in particulate form. Lower fractions of mostly particulate Au were released from the ashes (3 and 9%) of unspiked SSA. In conclusion, unaltered Au-NPs significantly leach from landfilled SSA, whereas the incorporation of Ag-NPs and CeO2-NPs as transformed species into the SSA matrix limits the leaching of (nano)particulate and dissolved Ag and Ce compounds., Conservative engineered nanoparticles (ENPs) that resist transformation during wastewater treatment and sludge incineration can be released from sewage sludge ash. Transient ENPs that undergo transformation are retained in the sewage sludge ash.

Extracorporeal blood purification has been applied to artificially support kidney or liver function. However, convection and diffusion based blood purification systems have limited removal rates for high molecular weight and hydrophobic molecules. This limitation is due to the finite volume of infusion and limited membrane permeability, respectively. Adsorption provides an attractive alternative for the removal of higher molecular weight compounds. The use of adsorption resins containing ion exchanging groups to capture specific molecules has become well-established. Instead of stationary adsorption resins, however, ion exchanging polymers may be immobilized on magnetic particles and serve as freely diffusing, mobile, high capacity solid phase of ion exchange chromatography. While small beads with high surface area are attractive in terms of mass transfer and binding, unifying high capturing capacity with rapid and quantitative bead recovery remains an issue. Therefore, most of the current magnetic ion exchangers are based on micron-sized beads or require long times to separate. In addition to unfavorable magnetic recovery rates, the usually poor cytocompatibility limits their applicability in biomedicine. Here, we report on the synthesis and performance of polycationic polymer coated magnetic nanoflowers (MNF) for highly efficacious anion capturing. We demonstrate accurate control over the polymer content and composition on the beads and show its direct influence on colloidal stability, capturing capacity and magnetic separability. We present the removal of clinically relevant targets by capturing bilirubin with capacities 2-fold higher than previous work as well as quantitative heparin removal. Additionally, we illustrate how copolymerization of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) with poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) leads to improved cytocompatibility of the polymer-coated MNF capturing agents while retaining high capturing capacities. Taken together, we present a nanoparticle/polymer material, which upon future in vivo validation, unifies high binding capacities and magnetic separability for rapid toxin capturing and hence fulfills key requirements of clinical utility.

Rare Earth Elements (REEs) are used in increasing amounts in technical applications and consumer products. However, to date, the contribution of industrial sources to the loads of individual REEs in wastewater streams have not been quantified. Here, we determine the REE contents in sludge collected from 63 wastewater treatment plants (WWTPs) across Switzerland. To quantify the industrial fraction of individual REEs in the sewage sludge, we develop two complementary approaches, based on REE ratios and REE pattern fitting. Unspecific (background) inputs, with REE patterns similar to the averaged REE pattern of soils collected across Switzerland, dominate the REE budget of most WWTPs. A few WWTPs receive significant REE inputs from specific industrial sources. Based on population equivalents of Switzerland, we estimate a total annual load of 4200 kg Cerium (Ce, 0.5 g Ce year-1 capita-1), with an industrial contribution of 2000 kg year-1. The latter agrees with estimates of probabilistic mass flow models for engineered nanoscale CeO2 particles discharged to the sewer network. About 7 kg year-1 of Samarium (Sm,total for Switzerland: 184 kg year-1 or 0.02 g Sm year-1 capita-1) and 3 kg year-1 of Europium (Eu,total for Switzerland: 44 kg year-1 or 0.005 g Eu year-1 capita-1) are assigned to industrial inputs from single WWTPs. Gadolinium (Gd) is used in the form of a stable complex as contrast agent in magnetic resonance imaging. Assuming 10% removal of Gd during wastewater treatment, we calculate an annual discharge of 90 kg of Gd from one individual WWTP to surface waters. WWTPs with exceptionally high industrial inputs of specific REEs warrant detailed investigations to identify the respective sources and to assess whether REE concentrations in effluents are elevated to the same degree., Water Research X, 11, ISSN:2589-9147

Bacterial infections are one of the main health concerns humanity faces today and bacterial resistances and protection mechanisms are set to aggravate the issue in the coming years. An increasing number of bacterial strains evades antibiotic treatment by hiding inside cells. Conventional antimicrobial agents are unable to penetrate or be retained in the infected mammalian cells. Recent approaches to overcome these limitations have focused on load-carrier systems, requiring a triggered discharge leading to complex release kinetics. The unison of potent antimicrobial activity with high mammalian cell compatibility is a prerequisite for intracellular activity, which is not well-met by otherwise well-established inorganic systems, such as silver-based nanoparticles. In this work, load and carrier are combined into one functional inorganic nanoparticle system, which unites antimicrobial activity with mammalian cell compatibility. These multicomponent nanohybrids based on cerium oxide are produced in one step, yet unite complex materials. The nanoparticles form suprastructures of similar size and surface charge as bacteria, therefore facilitating the uptake into the same subcellular compartments, where they unleash their antibacterial effect. Such intrinsically antibacterial nanohybrids significantly reduce bacterial survival inside macrophages without harming the latter. Furthermore, blocking of nanoparticle endocytosis and subcellular electron microscopy elucidate the mechanism of action. Taken together, this work presents the first demonstration of antibacterial activity of ceria-based nanoparticles inside of mammalian cells and offers a route to straightforward and robust intracellular antibacterial agents that do not depend on payload delivery or biological constituents., Ceria/bioglass nanohybrids significantly reduce bacterial survival inside human cells without harming the latter and overcome major shortcomings of conventional antibiotics.

Implant infections due to bacterial biofilms constitute a major healthcare challenge today. One way to address this clinical need is to modify the implant surface with an antimicrobial nanomaterial. Among such nanomaterials, nanosilver is arguably the most powerful one, due to its strong and broad antimicrobial activity. However, there is still a lack of understanding on how physicochemical characteristics of nanosilver coatings affect their antibiofilm activity. More specifically, the contributions of silver (Ag)+ ion-mediated vs. contact-based mechanisms to the observed antimicrobial activity are yet to be elucidated. To address this knowledge gap, we produce here nanosilver coatings on substrates by flame aerosol direct deposition that allows for facile control of the coating composition and Ag particle size. We systematically study the effect of (i) nanosilver content in composite Ag silica (SiO2) coatings from 0 (pure SiO2) up to 50 wt%, (ii) the Ag particle size and (iii) the coating thickness on the antibiofilm activity against Staphylococcus aureus (S. aureus), a clinically-relevant pathogen often present on the surface of surgically-installed implants. We show that the Ag+ ion concentration in solution largely drives the observed antibiofilm effect independently of Ag size and coating thickness. Furthermore, co-incubation of both pure SiO2 and nanosilver coatings in the same well also reveals that the antibiofilm effect stems predominantly from the released Ag+ ions, which is especially pronounced for coatings featuring the smallest Ag particle sizes, rather than direct bacterial contact inhibition. We also examine the biocompatibility of the developed nanosilver coatings in terms of pre-osteoblastic cell viability and proliferation, comparing it to that of pure SiO2. This study lays the foundation for the rational design of nanosilver-based antibiofilm implant coatings., Journal of Colloid and Interface Science, 608 (3), ISSN:0021-9797, ISSN:1095-7103

Nanoparticle-based radio-enhancement has the potential to improve cancer cell eradication by augmenting the photoelectric cross-section of targeted cancer cells relative to the healthy surroundings. Encouraging results have been reported for various nanomaterials, including gold and hafnia. However, the lack of scalable synthesis methods and comparative studies is prohibitive to rationalized material design and hampers translation of this promising cancer management strategy. Here, we present a scalable (>100 g day–1) and sterile alternative to conventional batch synthesis of group IV metal oxides (TiO2, ZrO2, and HfO2), which yields near-monodisperse ultrasmall metal oxide nanoparticles with radio-enhancement properties. Access to group IV oxide nanoparticles, which solely differ in atomic number but otherwise exhibit comparable morphologies, sizes, and surface chemistries, enables the direct comparison of their radio-enhancement properties to rationally guide material selection for optimal radio-enhancement performance. We show that the metal oxide nanoparticles exhibit atomic-number-dependent radio-enhancement in cancer cells (HT1080 and HeLa), which is attenuated to baseline levels in normal fibroblasts (normal human dermal fibroblasts). The observed radio-enhancement effects show excellent agreement with physical dose enhancement and nanoparticle dosimetry calculations. Direct benchmarking against gold nanoparticles, the current gold standard in the field, rationalizes the use of hafnia nanoparticles based on their radio-enhancement performance, which is superior to equi-sized gold nanoparticles. Taken together, the competitive radio-enhancement properties for near-monodisperse nanoparticles produced by scalable and sterile flame spray synthesis offer a route to overcoming key roadblocks in the translation of nanoparticle-based radio-enhancers., Chemistry of Materials, 33 (9), ISSN:0897-4756

Nanotechnology is identified as a key enabling technology due to its potential to contribute to economic growth and societal well-being across industrial sectors. Sustainable nanotechnology requires a scientifically based and proportionate risk governance structure to support innovation, including a robust framework for environmental risk assessment (ERA) that ideally builds on methods established for conventional chemicals to ensure alignment and avoid duplication. Exposure assessment developed as a tiered approach is equally beneficial to nano-specific ERA as for other classes of chemicals. Here we present the developing knowledge, practical considerations and key principles need to support exposure assessment for engineered nanomaterials for regulatory and research applications.

Radiotherapy is an integral and highly effective part of cancer therapy, applicable in over 50% of patients affected by cancer. Due to the low specificity of the X-ray irradiation, the maximal radiation dose is greatly limited in order to avoid damage to surrounding healthy tissue. The limitations in applicable dose oftentimes result in the survival of a subpopulation of radio-resistant cells that then cause cancer reoccurence. Approaches based on tumor-targeted high atomic number inorganic nanoparticles have been proposed to locally increase the photoelectric absorption cross-section of tumors relative to healthy tissue. However, the complex interplay between the nanoparticle radio-enhancers and the tumor tissue has led to poor translation of in vitro findings to (pre)clinics. Here, we report the development of a tumor microtissue model along with analytical imaging for the quantitative assessment of nanoparticle-based radio-enhancement as a function of nanoparticle size, uptake and intratissural distribution. The advanced in vitro model exhibits key features of cancerous tissues, including diminished susceptibility to drugs and attenuated response to nanoparticle treatment compared to corresponding conventional 2D cell cultures. Whereas radio-enhancement effects between 2D and 3D cell cultures were comparable for 5 nm gold particles, the limited penetration of 50 nm gold nanoparticles into 3D microtissues led to a significantly reduced radio-enhancement effect in 3D compared to 2D. Taken together, tumor microtissues, which in stark contrast to 2D cell culture exhibit tissue-like features, may provide a valuable high-throughput intermediate pre-selection step in the preclinical translation of nanoparticle-based radio-enhancement therapy designs., Nanoscale Advances, 2 (7), ISSN:2516-0230

Emissions of Ce from anthropogenic activities (anthropogenic Ce) into urban wastewater systems and the environment result from its widespread industrial use (abrasives, catalysts, nanotechnology). Because Ce in sewage sludge can also be of geogenic origin, the quantification of anthropogenic Ce in sewage sludge remains elusive. In this study, we evaluated the suitability of Ce oxidation state and rare earth element (REE) patterns for the quantification of anthropogenic Ce fractions in sewage sludge. A diverse set of soil samples served to gain baseline information on geogenic Ce. Geogenic Ce in the soils was characterized by high Ce(III) fractions (≥70%) and their REE patterns were comparable to the REE patterns of the upper continental crust. The sewage sludges contained on average ∼80% Ce(IV) (range 18–108%), pointing to the importance of anthropogenic inputs of Ce(IV). The quantification of the anthropogenic Ce fraction based on Ce oxidation state, however, was associated with considerable uncertainty because geogenic and anthropogenic Ce cannot exclusively be assigned to Ce(III) and Ce(IV), respectively. The REE patterns of most sewage sludges indicated a clear enrichment of Ce compared to heavier REE. Based on the assumption that the industrially used Ce is free of (most) other REE, we estimated the fraction of anthropogenic Ce in the sludges based on individual Ce/REE ratios. For the individual sludges the anthropogenic contributions were very variable (10–100%) but consistent fractions were obtained for individual sludges when calculated based on Ce/Dy (dysprosium), Ce/Er (erbium) and Ce/Eu (europium) ratios. Electron microscopy analysis of sludges dominated by anthropogenic Ce revealed that the Ce was mostly contained in nanoscale particles devoid of elements characteristic of Ce-bearing minerals. Thus, anthropogenic Ce contents derived from REE patterns may be used to validate current mass flow models for engineered CeO2 nanoparticles., Graphical abstract Image 1, Highlights • Characterization of Ce redox speciation in a set of different soils and sewage sludges using XANES. • Oxidation state of Ce from industrial Ce inputs to sludge can vary considerably. • Ce:La ratios in sewage sludge are often distorted by industrial La inputs. • The use of REE patterns yields a robust quantification of industrial Ce. • Ce-bearing particles of industrial origin in the sludge often occur in the nanoscale.

Sulfidation of copper oxide nanoparticles (CuO NPs) in urban wastewater systems is expected to influence their impact on the environment. However, the kinetics of this reaction has not been studied to date and the reaction mechanism remains largely unexplored. We therefore investigated the sulfidation kinetics of CuO NPs reacted with bisulfide (HS−) at concentrations relevant to wastewater systems. Pristine CuO NPs (50 nm, 7.7 μM) were reacted with HS− (26.4–105.6 μM) in oxic solutions buffered to pH 8.0. The reaction progress was monitored using silver nitrate to quench the reaction and selectively dissolve the copper sulfides (CuxS) and zincon to spectrophotometrically quantify the released Cu2+. In addition, the reaction products were characterized at selected time points using analytical electron microscopy and X-ray absorption spectroscopy (XAS). The sulfidation rate of the CuO NPs was best described by a pseudo first order rate law and the corresponding half-life times ranged between 1 and 6 minutes. XAS results showed that crystalline CuO NPs rapidly transformed into amorphous CuxS and gradually into crystalline CuS (covellite). The comparable size of pristine and transformed primary particles, the similar morphology of their aggregates, and the initial formation of CuO–CuxS core–shell structures revealed by analytical electron microscopy suggest that the initial sulfidation occurred via a direct conversion reaction mechanism. Our findings suggest that CuO NPs released from various sources into wastewater will rapidly transform into amorphous CuxS and eventually recrystallize into covellite.

Engineered nanoparticles (NP) discharged to sewers are efficiently retained by wastewater treatment plants and accumulate in the sewage sludge, which is commonly digested. The resulting biosolids are either used as fertilizer or incinerated. In this study, we address the transformation of Cu and Zn during sewage sludge incineration and evaluate whether the form of Cu or Zn (nanoparticulate versus dissolved) added to the digested sewage sludge affects the fate of the metals during incineration. We spiked CuO-NP, dissolved CuSO4, ZnO-NP, or dissolved ZnSO4 into anaerobically digested sewage sludge to reach Cu and Zn concentrations of ≈2500 and ≈3700 mg/kg and maintained the sludge under mesophilic, anaerobic conditions for 24 h. Subsequently, the sludge was incinerated in a pilot fluidized bed reactor. The speciation of Cu and Zn in the sludge, derived from X-ray absorption spectroscopy measurements, was dominated by sulfidic species, with >90% of Cu and >60% of Zn coordinated to reduced sulfur groups. In t...

Production volumes of cerium dioxide nanoparticles (CeO2 NP) are predicted to increase in the near future, which will result in increasing amounts of CeO2 NP discharged into wastewater systems and their accumulation in the sewage sludge. At the same time, thermal treatments of sewage sludge, especially incineration, are gaining in importance. Therefore, knowledge on the physical–chemical transformations of CeO2 NP during wastewater treatment and sludge incineration is critical for assessing possible (eco-) toxicological effects related to the increased use of CeO2 NP. We, thus, incinerated unspiked municipal sewage sludge as well as sludge spiked with CeO2 of different particle sizes (4 nm (CeO2-s1), 26 nm (CeO2-s2) and >16 μm (CeO2-s3)) in a pilot fluidized bed reactor to investigate the (size dependent) transformation of CeO2 under conditions mimicking full-scale incineration facilities. We used Ce K- and LIII-edge X-ray absorption spectroscopy (XAS) complemented by analytical electron microscopy to assess the changes in Ce speciation and to characterize the morphology of the pristine and the transformed Ce-(nano)particles. After one week of incubation in digested sludge under anaerobic conditions, CeO2-s1 already showed partial reduction (≈40%) to a Ce(III)-phase. Cerium dioxide of larger particle size (CeO2-s2 and -s3) was less reactive and did not show any detectable reduction within the same reaction time. Incineration of the sludge in general led to a further reduction of Ce, irrespective of whether the Ce was spiked (CeO2-s1, CeO2-s2, CeO2-s3) or already present in the sludge. Reduction during incineration was nearly complete for CeO2-s1 but much less pronounced for CeO2-s2 and -s3. Ce(IV) in larger (primary-) particle sizes thus was more resistant to reduction during anaerobic digestion and incineration. In addition, elemental distribution maps of the CeO2-s1 fly ash revealed elevated Ce signal intensities evenly distributed over areas of several 100 nm. The complementary results obtained from spectroscopic and microscopic analyses indicate that incineration led to the reductive decomposition of the initial CeO2-s1 NP and the sequestration of Ce(III) into a mineralogical phase with probably allanite-like local Ce(III) coordination. Our results, thus, highlight the importance of particle size and the surrounding matrix both affecting the transformation of CeO2 during sewage sludge incineration.

Carbon nanotubes (CNTs) have numerous exciting potential applications and some that have reached commercialization. As such, quantitative measurements of CNTs in key environmental matrices (water, soil, sediment, and biological tissues) are needed to address concerns about their potential environmental and human health risks and to inform application development. However, standard methods for CNT quantification are not yet available. We systematically and critically review each component of the current methods for CNT quantification including CNT extraction approaches, potential biases, limits of detection, and potential for standardization. This review reveals that many of the techniques with the lowest detection limits require uncommon equipment or expertise, and thus, they are not frequently accessible. Additionally, changes to the CNTs (e.g., agglomeration) after environmental release and matrix effects can cause biases for many of the techniques, and biasing factors vary amongst the techniques. Five case studies are provided to illustrate how to use this information to inform responses to real-world scenarios such as monitoring potential CNT discharge into a river or ecotoxicity testing by a testing laboratory. Overall, substantial progress has been made in improving CNT quantification during the past ten years, but additional work is needed for standardization, development of extraction techniques from complex matrices, and multi-method comparisons of standard samples to reveal the comparability of techniques.

The understanding of living systems and their building blocks relies on the assessment of structure-function relationships at the nanoscale. Although electron microscopy (EM) gives access to ultrastructural imaging with nanometric resolution, the unambiguous localization of specific molecules is challenging. An EM approach capable of localizing biomolecules with respect to the cellular ultrastructure will offer a direct route to the molecular blueprints of biological systems. In an approach departing from conventional correlative imaging, an electron beam may be used as excitation source to generate optical emission with nanometric resolution, that is, cathodoluminescence (CL). Once suitable luminescent labels become available, CL may be harnessed to enable identification of biomolecule labels based on spectral signatures rather than electron density and size. This work presents CL-enabled immunolabeling based on rare-earth element doped nanoparticle-labels allowing specific molecules to be visualized at nanoscale resolution in the context of the cellular ultrastructure. Folic acid decorated nanoparticles exhibiting single particle CL emission are employed to specifically label receptors and identify characteristic receptor clustering on the surface of cancer cells. This demonstration of CL immunotargeting gives access to protein localization in the context of the cellular ultrastructure and paves the way for immunolabeling of multiple proteins in EM.

Dissolved organic matter (DOM) influences the colloidal properties of engineered nanomaterials (ENMs) and impacts their transport and transformation in the environment. Sulfidation affects the fate and the ecological effects of released chalcophile ENMs. For copper oxide nanoparticles (CuO-NPs), the sulfidation and its kinetics have been described. However, the influence of DOM on this reaction has not been investigated yet. In wastewater systems, having high bisulfide contents, the DOM mainly consists of proteins, polysaccharides and humic substances. We therefore investigated the influence of the organic compounds bovine serum albumin (BSA, model protein), alginate (ALG, model polysaccharide), and polyacrylic acid (PAA, natural organic matter analogue) as well as that of natural humic acid (HA) and filtered wastewater (FW) on the sulfidation of CuO-NPs. Experiments were conducted in solutions buffered to pH 8.0 at concentrations of 1.3 mM CuO and ∼3.2 mM HS−. Increasing amounts of organic compounds were added to reach concentrations of 10–1000 mg L−1. Reacted CuO-NPs were collected at selected time points and characterized using Cu K-edge X-ray absorption spectroscopy and analytical electron microscopy. The sulfidation of the CuO-NPs was complete after 3 h in all experiments, except in the presence of 1000 mg L−1 BSA where ∼30% of CuO remained untransformed. Complete sulfidation of the CuO-NPs as observed in experiments conducted in FW suggests quantitative sulfidation of CuO-NPs in real wastewater. Without organic compounds, initially formed amorphous CuxS transformed into covellite over time. The presence of BSA, HA, ALG, and FW (but not PAA) hampered this transformation resulting in higher fractions of CuxS after sulfidation. Different amounts of CuxS with sizes of 10 kDa up to 10 nm formed during sulfidation depending on the type of organic compound. The properties of the CuxS-NPs formed by CuO-NP sulfidation must be considered when assessing their environmental impact.

Among a wide range of possible applications of nanotechnology in agriculture, there has been a particular interest in developing novel nanoagrochemicals. While some concerns have been expressed regarding altered risk profile of the new products, many foresee a great potential to support the necessary increase in global food production in a sustainable way. A critical evaluation of nanoagrochemicals against conventional analogues is essential to assess the associated benefits and risks. In this assessment, recent literature was critically analysed to determine the extent to which nanoagrochemicals differ from conventional products. Our analysis was based on 78 published papers and shows that median gain in efficacy relative to conventional products is about 20-30%. Environmental fate of agrochemicals can be altered by nanoformulations, but changes may not necessarily translate in a reduction of the environmental impact. Many studies lacked nano-specific quality assurance and adequate controls. Currently, there is no comprehensive study in the literature that evaluates efficacy and environmental impact of nanoagrochemicals under field conditions. This is a crucial knowledge gap and more work will thus be necessary for a sound evaluation of the benefits and new risks that nanoagrochemicals represent relative to existing products.

Analytical detection and quantification of multi-walled carbon nanotubes (MWCNTs) in complex matrices such as soils is very challenging. In an initial approach to this task, we identify MWCNTs by making use of their different (e.g., rod-like) shape compared to other (native) soil particles and in particular soot, which is ubiquitously present in soils. A shape factor ρ, determined using asymmetric flow field-flow fractionation coupled to multi-angle light scattering (aF4-MALS), was used to discriminate MWCNTs of different aspect ratios, as well as mixtures of soot and MWCNTs, in pure suspensions. MALS results were additionally confirmed using automated electron microscopy image analysis. We then analyzed different soil types which consistently showed ρ-values that differed from pure MWCNTs. To test the performance of the method for MWCNT detection in such complex matrices, we conducted standard additions of a MWCNT as well as soot to an agricultural soil. Extracts from these MWCNT-spiked soils showed increased ρ-values compared to soot-spiked or native soil. The method detection limit for the MWCNT was 1.6 to 4.0 mg g−1 soil and lies within the range of commonly used black carbon quantification methods, but is much higher than any currently predicted environmental concentration. Additionally, the method is currently limited by a relatively narrow dynamic range of ρ. Despite these limitations, our results suggest that aF4-MALS provides specific shape information that may be linked to an actual MWCNT presence in soils. Further method improvement potential is outlined along different steps of the workflow.

Background Agricultural soils represent a potential sink for increasing amounts of different nanomaterials that nowadays inevitably enter the environment. Knowledge on the relation between their actual exposure concentrations and biological effects on crops and symbiotic organisms is therefore of high importance. In this part of a joint companion study, we describe the vertical translocation as well as plant uptake of three different titanium dioxide (nano-)particles (TiO2 NPs) and multi-walled carbon nanotubes (MWCNTs) within a pot experiment with homogenously spiked natural agricultural soil and two plant species (red clover and wheat). Results TiO2 NPs exhibited limited mobility from soil to leachates and did not induce significant titanium uptake into both plant species, although average concentrations were doubled from 4 to 8 mg/kg Ti at the highest exposures. While the mobility of MWCNTs in soil was limited as well, microwave-induced heating suggested MWCNT-plant uptake independent of the exposure concentration. Conclusions Quantification of actual exposure concentrations with a series of analytical methods confirmed nominal ones in soil mesocosms with red clover and wheat and pointed to low mobility and limited plant uptake of titanium dioxide nanoparticles and carbon nanotubes., Journal of Nanobiotechnology, 14 (1), ISSN:1477-3155

Scientific publications and patents on nanomaterials (NM) used in plant protection or fertilizer products have exponentially increased since the millennium shift. While the United States and Germany have published the highest number of patents, Asian countries released most scientific articles. About 40% of all contributions deal with carbon-based NM, followed by titanium dioxide, silver, silica, and alumina. Nanomaterials come in many diverse forms (surprisingly often ≫100 nm), from solid doped particles to (often nonpersistent) polymer and oil-water based structures. Nanomaterials serve equally as additives (mostly for controlled release) and active constituents. Product efficiencies possibly increased by NM should be balanced against enhanced environmental NM input fluxes. The dynamic development in research and its considerable public perception are in contrast with the currently still very small number of NM-containing products on the market. Nanorisk assessment and legislation are largely in their infancies.

Hyperspectral imaging with enhanced darkfield microscopy (HSI-M) possesses unique advantages in its simplicity and non-invasiveness. In consideration of the urgent need for profound knowledge on the behavior and effects of engineered nanoparticles (NPs), here, we determined the capability of HSI-M for examining cellular uptake of different metal-based NPs, including nanosized metals (silver and gold, both citrate stabilized), metal oxides (copper oxide and titanium dioxide), and CdSe/ZnS core/shell quantum dots at subtoxic concentrations. Specifically, we demonstrated that HSI-M can be used to detect and semi-quantify these NPs in the ciliated protozoan Tetrahymena thermophila as a model aquatic organism. Detection and semi-quantification were achieved on the basis of spectral libraries for the NPs suspended in extracellular substances secreted by this single-celled organism, accounting for matrix effects. HSI-M was able to differentiate between NP types, provided that spectral profiles were significantly different from each other. This difference, in turn, depended upon NP type, size, agglomeration status, and position relative to the focal plane. As an exception among the NPs analyzed in this study, titanium dioxide NPs showed spectral similarities compared to cell material of unexposed control cells, leading to false positives. High biological variability resulted in highly variable uptake of NPs in cells of the same sample as well as between different exposures. We therefore encourage the development of techniques able to reduce the currently long analysis times that still hamper the acquisition of statistically strong data sets. Overall, this study demonstrates the potential and challenges of HSI-M in monitoring cellular uptake of synthetic NPs.

Titanium dioxide nanoparticles (TiO2 NPs) are in consideration to be used in plant protection products. Before these products can be placed on the market, ecotoxicological tests have to be performed. In this study, the nitrogen fixing bacterium Rhizobium trifolii and red clover were exposed to two TiO2 NPs, i.e., P25, E171 and a non-nanomaterial TiO2. Growth of both organisms individually and their symbiotic root nodulation were investigated in liquid and hydroponic systems. While 23 and 18 mg l(-1) of E171 and non-nanomaterial TiO2 decreased the growth rate of R. trifolii by 43 and 23% respectively, P25 did not cause effects. Shoot length of red clover decreased between 41 and 62% for all tested TiO2 NPs. In 21% of the TiO2 NP treated plants, no nodules were found. At high concentrations certain TiO2 NPs impaired R. trifolii as well as red clover growth and their symbiosis in the hydroponic systems.

Background Nanoparticles are produced and used worldwide and are released to the environment, e.g., into soil systems. Titanium dioxide (TiO2) nanoparticles (NPs), carbon nanotubes (CNTs) and cerium dioxide (CeO2) NPs are among the ten most produced NPs and it is therefore important to test, whether these NPs affect plants and symbiotic microorganisms that help plants to acquire nutrients. In this part of a joint companion study, we spiked an agricultural soil with TiO2 NPs, multi walled CNTs (MWCNTs), and CeO2 NPs and we examined effects of these NP on red clover, biological nitrogen fixation by rhizobia and on root colonization of arbuscular mycorrhizal fungi (AMF). We also tested whether effects depended on the concentrations of the applied NPs. Results Plant biomass and AMF root colonization were not negatively affected by NP exposure. The number of flowers was statistically lower in pots treated with 3 mg kg−1 MWCNT, and nitrogen fixation slightly increased at 3000 mg kg−1 MWCNT. Conclusions This study revealed that red clover was more sensitive to MWCNTs than TiO2 and CeO2 NPs. Further studies are necessary for finding general patterns and investigating mechanisms behind the effects of NPs on plants and plant symbionts. Electronic supplementary material The online version of this article (doi:10.1186/s12951-016-0188-7) contains supplementary material, which is available to authorized users.