Reusable magnetic mixture of CuFe2O4-Fe2O3 and TiO2 for photocatalytic degradation of pesticides in water

Photocatalysis is a promising treatment method to remove pollutants from water. TiO2-P25 is a commercially available model photocatalyst, which very efficiently degrades organic pollutants under UVA light exposure. However, the collection and the recovery of TiO2-P25 from cleaned water poses significant difficulties, severely limiting its usability. To address this challenge, we have prepared a sintered mixture of TiO2-P25 nanomaterials and magnetic CuFe2O4-Fe2O3 nanocomposites. The mixture material was shown to contain spinel ferrite, hematite and maghemite structures, copper predominantly in Cu2+ and iron predominantly in Fe3+ state. The CuFe2O4-Fe2O3 and TiO2-P25 mixture demonstrated magnetic collectability from processed water and photocatalytic activity, which was evidenced through the successful photodegradation of the herbicide 2,4-D. Our findings suggest that the sintered mixture of CuFe2O4-Fe2O3 and TiO2-P25 holds a promise for improving photocatalytic water treatment, with the potential to overcome current photocatalyst recovery issues.

Material-Intrinsic NIR-Fluorescence Enables Image-Guided Surgery for Ceramic Fracture Removal

Hip arthroplasty effectively treats advanced osteoarthritis and is therefore entitled as "operation of the 20th century." With demographic shifts, the USA alone is projected to perform up to 850 000 arthroplasties annually by 2030. Many implants now feature a ceramic head, valued for strength and wear resistance. Nonetheless, a fraction, up to 0.03% may fracture during their lifespan, demanding complex removal procedures. To address this, a radiation-free, fluorescence-based image-guided surgical technique is presented. The method uses the inherent fluorescence of ceramic implant materials, demonstrated through chemical and optical analysis of prevalent implant types. Specifically, Biolox delta implants exhibited strong fluorescence around 700 nm with a 74% photoluminescence quantum yield. Emission tails are identified extending into the near-infrared (NIR-I) biological transparency range, forming a vital prerequisite for the label-free visualization of fragments. This ruby-like fluorescence could be attributed to Cr within the zirconia-toughened alumina matrix, enabling the detection of even deep-seated millimeter-sized fragments via camera-assisted techniques. Additionally, fluorescence microscopy allowed detection of µm-sized ceramic particles, enabling debris visualization in synovial fluid as well as histological samples. This label-free optical imaging approach employs readily accessible equipment and can seamlessly transition to clinical settings without significant regulatory barriers, thereby enhancing the safety, efficiency, and minimally invasive nature of fractured ceramic implant removal procedures.

Protein Aggregation on Metal Oxides Governs Catalytic Activity and Cellular Uptake

Engineering of catalytically active inorganic nanomaterials holds promising prospects for biomedicine. Catalytically active metal oxides show applications in enhancing wound healing but have also been employed to induce cell death in photodynamic or radiation therapy. Upon introduction into a biological system, nanomaterials are exposed to complex fluids, causing interaction and adsorption of ions and proteins. While protein corona formation on nanomaterials is acknowledged, its modulation of nanomaterial catalytic efficacy is less understood. In this study, proteomic analyses and nano-analytic methodologies quantify and characterize adsorbed proteins, correlating this protein layer with metal oxide catalytic activity in vitro and in vivo. The protein corona comprises up to 280 different proteins, constituting up to 38% by weight. Enhanced complement factors and other opsonins on nanocatalyst surfaces lead to their uptake into macrophages when applied topically, localizing >99% of the nanomaterials in tissue-resident macrophages. Initially, the formation of the protein corona significantly reduces the nanocatalysts' activity, but this activity can be partially recovered in endosomal conditions due to the proteolytic degradation of the corona. Overall, the research reveals the complex relationship between physisorbed proteins and the catalytic characteristics of specific metal oxide nanoparticles, providing design parameters for optimizing nanocatalysts in complex biological environments.

Bioglass/ceria nanoparticle hybrids for the treatment of seroma: a comparative long-term study in rats

Background: Seroma formation is a common postoperative complication. Fibrin-based glues are typically employed in an attempt to seal the cavity. Recently, the first nanoparticle (NP)-based treatment approaches have emerged. Nanoparticle dispersions can be used as tissue glues, capitalizing on a phenomenon known as 'nanobridging'. In this process, macromolecules such as proteins physically adsorb onto the NP surface, leading to macroscopic adhesion. Although significant early seroma reduction has been shown, little is known about long-term efficacy of NPs. The aim of this study was to assess the long-term effects of NPs in reducing seroma formation, and to understand their underlying mechanism. Methods: Seroma was surgically induced bilaterally in 20 Lewis rats. On postoperative day (POD) 7, seromas were aspirated on both sides. In 10 rats, one side was treated with NPs, while the contralateral side received only NP carrier solution. In the other 10 rats, one side was treated with fibrin glue, while the other was left untreated. Seroma fluid, blood and tissue samples were obtained at defined time points. Biochemical, histopathological and immunohistochemical assessments were made. Results: NP-treated sides showed no macroscopically visible seroma formation after application on POD 7, in stark contrast to the fibrin-treated sides, where 60% of the rats had seromas on POD 14, and 50% on POD 21. At the endpoint (POD 42), sides treated with nanoparticles (NPs) exhibited significant macroscopic differences compared to other groups, including the absence of a cavity, and increased fibrous adhesions. Histologically, there were more macrophage groupings and collagen type 1 (COL1) deposits in the superficial capsule on NP-treated sides. Conclusion: NPs not only significantly reduced early manifestations of seroma and demonstrated an anti-inflammatory response, but they also led to increased adhesion formation over the long term, suggesting a decreased risk of seroma recurrence. These findings highlight both the adhesive properties of NPs and their potential for clinical therapy.

Embedding Pd into SnO2 drastically enhances gas sensing

Combustion aerosol processes can uniquely embed noble metals into semiconducting particles. Here, monocrystalline SnO2 particles embedded with Pd and/or PdOx were made by flame spray pyrolysis (FSP) of appropriate precursors through microexplosions by droplet-to-particle conversion as the crystal size was proportional to the cube root of precursor solution concentration, C. These particles were air-annealed and leached with nitric acid for removal of metallic Pd from their surface. The SnO2 crystal size varied from 11 to 24 nm and was in close agreement with the primary particle size determined by nitrogen adsorption. The embedded fraction of Pd ranged from about 30 to 80% of the nominal Pd-content. This was achieved by judiciously varying the C, Pd content and the ratio of precursor solution to dispersion oxygen flowrates during FSP. The response of sensors made by doctor blading films of such particles to 1 ppm of acetone and CO was evaluated at 350 °C and 50% relative humidity. Embedding Pd/PdOx into SnO2 significantly increased the sensor response: 2-6 times over that of pure or conventionally-made Pd-containing SnO2 sensors at low nominal Pd-contents (0.2 mol%). For higher ones (i.e. 1 mol% Pd), the sensor response was enhanced by up to two orders of magnitude. This is attributed to Pd atoms in the SnO2 lattice near the particle surface and/or Pd/PdOx clusters acting as nanoelectrodes into SnO2 films and altering their transducing properties as shown by high resolution electron microscopy, XPS and baseline resistance measurements of pure and Pd-embedded SnO2 sensing films.

Boron Nitride Nanosheets Induce Lipid Accumulation and Autophagy in Human Alveolar Lung Epithelial Cells Cultivated at Air-Liquid Interface

Hexagonal boron nitride (hBN) is an emerging 2D material attracting significant attention due to its superior electrical, chemical, and therapeutic properties. However, inhalation toxicity mechanisms of hBN in human lung cells are poorly understood. Here, cellular interaction and effects of hBN nanosheets is investigated in alveolar epithelial cells cultured on porous inserts and exposed under air-liquid interface conditions for 24 h. hBN is taken up by the cells as determined in a label-free manner via RAMAN-confocal microscopy, ICP-MS, TEM, and SEM-EDX. No significant (p > 0.05) effects are observed on cell membrane integrity (LDH release), epithelial barrier integrity (TEER), interleukin-8 cytokine production or reactive oxygen production at tested dose ranges (1, 5, and 10 µg cm-2 ). However, it is observed that an enhanced accumulation of lipid granules in cells indicating the effect of hBN on lipid metabolism. In addition, it is observed that a significant (p < 0.05) and dose-dependent (5 and 10 µg cm-2 ) induction of autophagy in cells after exposure to hBN, potentially associated with the downstream processing and breakdown of excess lipid granules to maintain lipid homeostasis. Indeed, lysosomal co-localization of lipid granules supporting this argument is observed. Overall, the results suggest that the continuous presence of excess intracellular lipids may provoke adverse outcomes in the lungs.

X-ray radio-enhancement by Ti3C2Tx MXenes in soft tissue sarcoma

Radiotherapy is a cornerstone of cancer treatment. However, due to the low tissue specificity of ionizing radiation, damage to the surrounding healthy tissue of the tumor remains a significant challenge. In recent years, radio-enhancers based on inorganic nanomaterials have gained considerable interest. Beyond the widely explored metal and metal oxide nanoparticles, 2D materials, such as MXenes, could present potential benefits because of their inherently large specific surface area. In this study, we highlight the promising radio-enhancement properties of Ti3C2Tx MXenes. We demonstrate that atomically thin layers of titanium carbides (Ti3C2Tx MXenes) are efficiently internalized and well-tolerated by mammalian cells. Contrary to MXenes suspended in aqueous buffers, which fully oxidize within days, yielding rice-grain shaped rutile nanoparticles, the MXenes internalized by cells oxidize at a slower rate. This is consistent with cell-free experiments that have shown slower oxidation rates in cell media and lysosomal buffers compared to dispersants without antioxidants. Importantly, the MXenes exhibit robust radio-enhancement properties, with dose enhancement factors reaching up to 2.5 in human soft tissue sarcoma cells, while showing no toxicity to healthy human fibroblasts. When compared to oxidized MXenes and commercial titanium dioxide nanoparticles, the intact 2D titanium carbide flakes display superior radio-enhancement properties. In summary, our findings offer evidence for the potent radio-enhancement capabilities of Ti3C2Tx MXenes, marking them as a promising candidate for enhancing radiotherapy.

Biochemical transformations of inorganic nanomedicines in buffers, cell cultures and organisms

The field of nanomedicine is rapidly evolving, with new materials and formulations being reported almost daily. In this respect, inorganic and inorganic-organic composite nanomaterials have gained significant attention. However, the use of new materials in clinical trials and their final approval as drugs has been hampered by several challenges, one of which is the complex and difficult to control nanomaterial chemistry that takes place within the body. Several reviews have summarized investigations on inorganic nanomaterial stability in model body fluids, cell cultures, and organisms, focusing on their degradation as well as the influence of corona formation. However, in addition to these aspects, various chemical reactions of nanomaterials, including phase transformation and/or the formation of new/secondary nanomaterials, have been reported. In this review, we discuss recent advances in our understanding of biochemical transformations of medically relevant inorganic (composite) nanomaterials in environments related to their applications. We provide a refined terminology for the primary reaction mechanisms involved to bridge the gaps between different disciplines involved in this research. Furthermore, we highlight suitable analytical techniques that can be harnessed to explore the described reactions. Finally, we highlight opportunities to utilize them for diagnostic and therapeutic purposes and discuss current challenges and research priorities.

Nanoanalytical Insights into the Stability, Intracellular Fate, and Biotransformation of Metal-Organic Frameworks

Metal-organic frameworks (MOFs) have found increasing applications in the biomedical field due to their unique properties and high modularity. Although the limited stability of MOFs in biological environments is increasingly recognized, analytical techniques have not yet been harnessed to their full potential to assess the biological fate of MOFs. Here, we investigate the environment-dependent biochemical transformations of widely researched nanosized MOFs (nMOFs) under conditions relevant to their medical application. We assess the chemical stability of antimicrobial zinc-based drug delivery nMOFs (Zn-ZIF-8 and Zn-ZIF-8:Ce) and radio-enhancer candidate nMOFs (Hf-DBA, Ti-MIL-125, and TiZr-PCN-415) containing biologically nonessential group IV metal ions. We reveal that even a moderate decrease in pH to values encountered in lysosomes (pH 4.5-5) leads to significant dissolution of ZIF-8 and partial dissolution of Ti-MIL-125, whereas no substantial dissolution was observed for TiZr-PCN-415 and Hf-DBA nMOFs. Exposure to phosphate-rich buffers led to phosphate incorporation in all nMOFs, resulting in amorphization and morphological changes. Interestingly, long-term cell culture studies revealed that nMOF (bio)transformations of, e.g., Ti-MIL-125 were cellular compartment-dependent and that the phosphate content in the nMOF varied significantly between nMOFs localized in lysosomes and those in the cytoplasm. These results illustrate the delicate nature and environment-dependent properties of nMOFs across all stages of their life cycle, including storage, formulation, and application, and the need for in-depth analyses of biotransformations for an improved understanding of structure-function relationships. The findings encourage the considerate choice of suspension buffers for MOFs because these media may lead to significant material alterations prior to application.

Metal-Organic Framework Mediated Radio-Enhancement Assessed in High-Throughput-Compatible 3D Tumor Spheroid Co-Cultures

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.

Multiscale Multimodal Investigation of the Intratissural Biodistribution of Iron Nanotherapeutics with Single Cell Resolution Reveals Co-Localization with Endogenous Iron in Splenic Macrophages

Imaging of iron-based nanoparticles (NPs) remains challenging because of the presence of endogenous iron in tissues that is difficult to distinguish from exogenous iron originating from the NPs. Here, an analytical cascade for characterizing the biodistribution of biomedically relevant iron-based NPs from the organ scale to the cellular and subcellular scales is introduced. The biodistribution on an organ level is assessed by elemental analysis and quantification of magnetic iron by electron paramagnetic resonance, which allowed differentiation of exogenous and endogenous iron. Complementary to these bulk analysis techniques, correlative whole-slide optical and electron microscopy provided spatially resolved insight into the biodistribution of endo- and exogenous iron accumulation in macrophages, with single-cell and single-particle resolution, revealing coaccumulation of iron NPs with endogenous iron in splenic macrophages. Subsequent transmission electron microscopy revealed two types of morphologically distinct iron-containing structures (exogenous nanoparticles and endogenous ferritin) within membrane-bound vesicles in the cytoplasm, hinting at an attempt of splenic macrophages to extract and recycle iron from exogenous nanoparticles. Overall, this strategy enables the distinction of endo- and exogenous iron across scales (from cm to nm, based on the analysis of thousands of cells) and illustrates distribution on organ, cell, and organelle levels.

Encapsulated salts in velvet worm slime drive its hardening

Slime expelled by velvet worms entraps prey insects within seconds in a hardened biopolymer network that matches the mechanical strength of industrial polymers. While the mechanic stimuli-responsive nature and building blocks of the polymerization are known, it is still unclear how the velvet worms' slime hardens so fast. Here, we investigated the slime for the first time, not only after, but also before expulsion. Further, we investigated the slime's micro- and nanostructures in-depth. Besides the previously reported protein nanoglobules, carbohydrates, and lipids, we discovered abundant encapsulated phosphate and carbonate salts. We also detected CO₂ bubbles during the hardening of the slime. These findings, along with further observations, suggest that the encapsulated salts in expelled slime rapidly dissolve and neutralize in a baking-powder-like reaction, which seems to accelerate the drying of the slime. The proteins' conformation and aggregation are thus influenced by shear stress and the salts' neutralization reaction, increasing the slime's pH and ionic strength. These insights into the drying process of the velvet worm's slime demonstrate how naturally evolved polymerizations can unwind in seconds, and could inspire new polymers that are stimuli-responsive or fast-drying under ambient conditions.

Cellular fate and performance of group IV metal organic framework radioenhancers

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.

Evaluation of fiber and debris release from protective COVID-19 mask textiles and in vitro acute cytotoxicity effects

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.

Catalytic activity imperative for nanoparticle dose enhancement in photon and proton therapy

Nanoparticle-based radioenhancement is a promising strategy for extending the therapeutic ratio of radiotherapy. While (pre)clinical results are encouraging, sound mechanistic understanding of nanoparticle radioenhancement, especially the effects of nanomaterial selection and irradiation conditions, has yet to be achieved. Here, we investigate the radioenhancement mechanisms of selected metal oxide nanomaterials (including SiO₂, TiO₂, WO₃ and HfO₂), TiN and Au nanoparticles for radiotherapy utilizing photons (150 kVp and 6 MV) and 100 MeV protons. While Au nanoparticles show outstanding radioenhancement properties in kV irradiation settings, where the photoelectric effect is dominant, these properties are attenuated to baseline levels for clinically more relevant irradiation with MV photons and protons. In contrast, HfO₂ nanoparticles retain some of their radioenhancement properties in MV photon and proton therapies. Interestingly, TiO₂ nanoparticles, which have a comparatively low effective atomic number, show significant radioenhancement efficacies in all three irradiation settings, which can be attributed to the strong radiocatalytic activity of TiO₂, leading to the formation of hydroxyl radicals, and nuclear interactions with protons. Taken together, our data enable the extraction of general design criteria for nanoparticle radioenhancers for different treatment modalities, paving the way to performance-optimized nanotherapeutics for precision radiotherapy.

Nanoparticles have recently received attention in radiation therapy since they can act as radioenhancers. In this article, the authors report on the dose enhancement capabilities of a series of nanoparticles based on their metal core composition and beam characteristics, obtaining designing criteria for their optimal performance in specific radiotreatments.

The Role of Inorganics in Preeclampsia Assessed by Multiscale Multimodal Characterization of Placentae

Preeclampsia is one of the most dangerous diseases in pregnancy. Because of the hypertensive nature of preeclampsia, placental calcifications are believed to be a predictor for its occurrence, analogous to their role in cardiovascular diseases. However, the prevalence and the relevance of calcifications for the clinical outcome with respect to preeclampsia remains controversial. In addition, the role of other inorganic components present in the placental tissue in the development of preeclampsia has rarely been investigated. In this work, we therefore characterized inorganic constituents in placental tissue in groups of both normotensive and preeclamptic patients (N = 20 each) using a multi-scale and multi-modal approach. Examinations included elemental analysis (metallomics), sonography, computed tomography (CT), histology, scanning electron microscopy, X-ray fluorescence and energy dispersive X-ray spectroscopy. Our data show that tissue contents of several heavy metals (Al, Cd, Ni, Co, Mn, Pb, and As) were elevated whereas the Rb content was decreased in preeclamptic compared to normotensive placentae. However, the median mineral content (Ca, P, Mg, Na, K) was remarkably comparable between the two groups and CT showed lower calcified volumes and fewer crystalline deposits in preeclamptic placentae. Electron microscopy investigations revealed four distinct types of calcifications, all predominantly composed of calcium, phosphorus and oxygen with variable contents of magnesium in tissues of both maternal and fetal origin in both preeclamptic and normotensive placentae. In conclusion our study suggests that heavy metals, combined with other factors, can be associated with the development of preeclampsia, however, with no obvious correlation between calcifications and preeclampsia.

Antibiofilm activity of nanosilver coatings against Staphylococcus aureus

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.

Release of gold (Au), silver (Ag) and cerium dioxide (CeO2) nanoparticles from sewage sludge incineration ash

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.

Inorganic nanohybrids combat antibiotic-resistant bacteria hiding within human macrophages

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.

Quantification of individual Rare Earth Elements from industrial sources in sewage sludge

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.

Bi2O3 boosts brightness, biocompatibility and stability of Mn-doped Ba3(VO4)2 as NIR-II contrast agent

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.

Quantification of anthropogenic and geogenic Ce in sewage sludge based on Ce oxidation state and rare earth element patterns

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.

Impact of hypoxia-ischemia and dopamine treatment on dopamine receptor binding density in the preterm fetal sheep brain

Dopamine is often used to treat hypotension in preterm infants who are at risk of hypoxic-ischemic (HI) brain injury due to cerebral hypoperfusion and impaired autoregulation. There is evidence that systemically administered dopamine crosses the preterm blood-brain barrier. However, the effects of exogenous dopamine and cerebral HI on dopaminergic signaling in the immature brain are unknown. We determined the effect of HI and dopamine on D1 and D2 receptor binding and expressions of dopamine transporter (DAT) and tyrosine hydroxylase (TH) in the striatum of the preterm fetal sheep. Fetal sheep (99 days of gestation, term = 147days) were unoperated controls (n = 6) or exposed to severe HI using umbilical cord occlusion and saline infusion (UCO + saline, n = 8) or to HI with dopamine infusion (UCO + dopamine, 10 µg/kg/min, n = 7) for 74 h. D1 and D2 receptor densities were measured by autoradiography in vitro. DAT, TH, and cell death were measured using immunohistochemistry. HI resulted in cell death in the caudate nucleus and putamen, and dopamine infusion started before HI did not exacerbate or ameliorate these effects. HI led to reduced D1 and D2 receptor densities in the caudate nucleus and reduction in DAT protein expression in the caudate and putamen. Fetal brains exposed to dopamine in addition to HI were not different from those exposed to HI alone in these changes in dopaminergic parameters. We conclude that dopamine infusion does not alter the striatal cell death or the reductions in D1 and D2 receptor densities and DAT protein expression induced by HI in the preterm brain.NEW & NOTEWORTHY This is the first study on the effects of hypoxia-ischemia and dopamine treatment on the dopaminergic pathway in the preterm brain. In the striatum of fetal sheep (equivalent to ∼26-28 wk of human gestation), we demonstrate that hypoxia-ischemia leads to cell death, reduces D1 and D2 receptors, and reduces dopamine transporter. Intravenous dopamine infusion at clinical dosage used in preterm human infants does not alter the striatal cell death, D1 and D2 receptor density levels, and DAT protein expressions after hypoxia-ischemia in the preterm brain.

Correlative Cathodoluminescence Electron Microscopy: Immunolabeling Using Rare-Earth Element Doped Nanoparticles

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.

Key principles and operational practices for improved nanotechnology environmental exposure assessment

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.

Uptake, distribution and radio-enhancement effects of gold nanoparticles in tumor microtissues

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.

Tailoring the Colloidal Stability, Magnetic Separability, and Cytocompatibility of High-Capacity Magnetic Anion Exchangers

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.

Transformation of Nanoscale and Ionic Cu and Zn during the Incineration of Digested Sewage Sludge (Biosolids)

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 the ash, both Cu (>60%) and Zn (≈100%) were coordinated to oxygen. The chemical speciation of Cu and Zn in the ashes was independent of whether they were spiked in the dissolved or nanoparticulate form and closely matched the speciation of Cu and Zn observed in ashes from full-scale incinerators.

A critical evaluation of nanopesticides and nanofertilizers against their conventional analogues

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.

Correlation Between Depression and Cognitive Decline in Elderly Outpatients: A Preliminary Study

Introduction

Depressive disorder is common psychiatric morbidity among the elderly outpatients. It is also evident that cognitive disorders, ranging from mild cognitive impairment to severe dementia, are widely prevalent in the elderly coexistence of the above is quite common. Treatment for both conditions is quite challenging, aiming at symptomatic relief and improvement in functional status.

Objectives

To investigate the coexistence of depression and cognitive impairment in aged depressive outpatients, 65 years or older. Correlation of cognitive level and depressive symptomatology was measured.

Method

We used hamilton depression scale (HAM-D) and MMSE in 35 (mean age 68.2 years) depressed outpatients over 65-year-old. We excluded depressed schizophrenics and bipolar patient.

Results.

On a preliminary basis, a correlation between low MMSe and HAM-D (P < 0.05) was found. An interesting finding, though not measured primarily, was that low MMSE was accompanied with a low compliance with medication.

Conclusions

The mental deterioration that accompanies cognitive impairment is being widely studied and it is real complex. In our ongoing study previous findings are confirmed and can be interpreted both ways, i.e. depression is a risk factor for dementia and also the fact that existing dementia is positively correlated with a low HAM-D.

Compliance to medication is affected, among other variables, by the patients’ mental state.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Vertical transport and plant uptake of nanoparticles in a soil mesocosm experiment

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-016-0191-z) contains supplementary material, which is available to authorized users.

Effects of Titanium Dioxide Nanoparticles on Red Clover and Its Rhizobial Symbiont

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.

Effect of nanoparticles on red clover and its symbiotic microorganisms

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.

Quantification of Carbon Nanotubes in Environmental Matrices: Current Capabilities, Case Studies, and Future Prospects

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 among 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 multimethod comparisons of standard samples to reveal the comparability of techniques.

Potential of hyperspectral imaging microscopy for semi-quantitative analysis of nanoparticle uptake by protozoa

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.

Nanomaterials in plant protection and fertilization: current state, foreseen applications, and research priorities

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.

Assessment of suitability of tree species for the production of biomass on trace element contaminated soils

To alleviate the demand on fertile agricultural land for production of bioenergy, we investigated the possibility of producing biomass for bioenergy on trace element (TE) contaminated land. Soil samples and plant tissues (leaves, wood and bark) of adult willow (Salix sp.), poplar (Populus sp.), and birch (Betula pendula) trees were collected from five contaminated sites in France and Germany and analysed for Zn, Cd, Pb, Cu, Ca, and K. Cadmium concentration in tree leaves were correlated with tree species, whereas Zn concentration in leaves was site correlated. Birch revealed significantly lower leaf Cd concentrations (1.2-8.9 mg kg(-1)) than willow and poplar (5-80 mg kg(-1)), thus posing the lowest risk for TE contamination of surrounding areas. Birch displayed the lowest bark concentrations for Ca (2300-6200 mg kg(-1)) and K (320-1250 mg kg(-1)), indicating that it would be the most suitable tree species for fuel production, as high concentrations of K and Ca decrease the ash melting point which results in a reduced plant lifetime. Due to higher TE concentrations in bark compared to wood a small bark proportion in relation to the trunk is desirable. In general the bark proportion was reduced with the tree age. In summary, birch was amongst the investigated species the most suitable for biomass production on TE contaminated land.

The importance of baseline in identifying 8-OH-DPAT-induced effects on prepulse inhibition in rats

BACKGROUND AND PURPOSE

Prepulse inhibition (PPI) of the acoustic startle response is a model of sensorimotor gating which is disrupted in schizophrenia and other mental illnesses. We and others have shown that treatment with the 5-hydroxytryptamine-1A (5-HT(1A)) receptor agonist, 8-OH-DPAT, disrupts PPI in rats. In the present study, we highlight the importance of baseline levels on the effect of 8-OH-DPAT on PPI.

EXPERIMENTAL APPROACH

Adult male and female Sprague-Dawley rats were gonadectomised. These rats were treated with saline, 0.02 and 0.5 mg kg(-1) of 8-OH-DPAT using a random-sequence, repeated-measures protocol. The rats were allocated into high and low baseline groups depending on their baseline PPI observed after saline treatment.

KEY RESULTS

Treatment with 0.5 mg kg(-1) of 8-OH-DPAT significantly disrupted PPI in both male and female rats. In male rats only, 0.02 mg kg(-1) 8-OH-DPAT caused a small, but significant, increase in PPI. When these male rats were allocated to either a high or low baseline PPI group, 0.5 mg kg(-1) 8-OH-DPAT disrupted PPI in the high baseline group only. In contrast, treatment with 0.02 mg kg(-1) 8-OH-DPAT increased PPI only in the low baseline PPI group. There were no changes in the effect of 8-OH-DPAT administration in female rats when they were divided into high and low baseline PPI groups.

CONCLUSIONS AND IMPLICATIONS

The level of baseline PPI is an important variable that can influence the direction of drug effects induced by 8-OH-DPAT. The explanation for this phenomenon could be differential activation of pre- and postsynaptic 5-HT(1A) receptors.

Importance of animal models in schizophrenia research

OBJECTIVE

This review aims to summarize the importance of animal models for research on psychiatric illnesses, particularly schizophrenia.

METHOD AND RESULTS

Several aspects of animal models are addressed, including animal experimentation ethics and theoretical considerations of different aspects of validity of animal models. A more specific discussion is included on two of the most widely used behavioural models, psychotropic drug-induced locomotor hyperactivity and prepulse inhibition, followed by comments on the difficulty of modelling negative symptoms of schizophrenia. Furthermore, we emphasize the impact of new developments in molecular biology and the generation of genetically modified mice, which have generated the concept of behavioural phenotyping.

CONCLUSIONS

Complex psychiatric illnesses, such as schizophrenia, cannot be exactly reproduced in species such as rats and mice. Nevertheless, by providing new information on the role of neurotransmitter systems and genes in behavioural function, animal 'models' can be an important tool in unravelling mechanisms involved in the symptoms and development of such illnesses, alongside approaches such as post-mortem studies, cognitive and psychophysiological studies, imaging and epidemiology.

Assignment of enzyme substrate specificity by principal component analysis of aligned protein sequences: an experimental test using DNA glycosylase homologs

We have studied the relationship between amino acid sequence and substrate specificity in a DNA glycosylase family by characterizing experimentally the specificity of four new members of the family. We show that principal component analysis (PCA) of the sequence family correctly predicts the substrate specificity of one of the novel homologs even though conventional sequence analysis methods fail to group this homolog with other sequences of the same specificity. PCA also suggested, correctly, that another homolog characterized previously differs in its specificity from those sequences with which it clusters by conventional criteria. These results suggest that principal component analysis of sequence families can be a useful tool in annotating genome sequences when there is ambiguity concerning which subfamily a new homolog belongs to. Published 2000 Wiley-Liss, Inc.

Characterization of an 8-oxoguanine DNA glycosylase from Methanococcus jannaschii

A thermostable 8-oxoguanine (oxoG) DNA glycosylase from Methanococcus jannaschii has been expressed in Escherichia coli, purified, and characterized. The enzyme, which has been named mjOgg, belongs to the same diverse DNA glycosylase superfamily as the 8-oxoguanine DNA glycosylases from yeast (yOgg1) and human (hOgg1) but is substantially different in sequence. In addition, unlike its eukaryotic counterparts, which have a strong preference for oxoG.C base pairs, mjOgg has little specificity for the base opposite oxoG. mjOgg has both DNA glycosylase and DNA lyase (beta-elimination) activity, and the combined glycosylase/lyase activity occurs at a rate comparable with the glycosylase activity alone. Mutation of Lys-129, analogous to Lys-241 of yOgg1, abolishes glycosylase activity.

The C-terminal domain of the adenine-DNA glycosylase MutY confers specificity for 8-oxoguanine.adenine mispairs and may have evolved from MutT, an 8-oxo-dGTPase

MutY is an adenine-DNA glycosylase with specificity for mismatches involving 8-oxoguanine (oG.A) or guanine (G.A). In addition to a 25 kDa catalytic domain common to all members of its DNA glycosylase superfamily, MutY has a 14 kDa C-terminal domain. Sequence analyses suggest that this C-terminal domain is distantly related to MutT, a pyrophosphohydrolase specific for 2'-deoxy-8-oxoguanosine triphosphate (doGTP). Here we present biochemical evidence that the MutT-like domain of MutY is the principal determinant of oG specificity. First, MutY dissociates approximately 1500-fold more slowly from oG-containing product DNA than from G-containing product, but a truncated protein lacking the C-terminal domain dissociates as rapidly from oG-DNA as the full-length protein dissociates from G-DNA. Second, MutY removes adenine from oG.A mismatches almost 30-fold faster than from G.A mismatches in a pre-steady-state assay, but deletion of the C-terminal domain reduces this specificity for oG.A to less than 4-fold. The kinetic data are consistent with a model in which binding of oG to the C-terminal domain of MutY accelerates the pre-steady-state glycosylase reaction by facilitating adenine base flipping. The observation that oG specificity derives almost exclusively from the C-terminal domain of MutY adds credence to the sequence analyses and suggests that specificity for oG.A mismatches was acquired by fusion of a MutT-like protein onto the core catalytic domain of an adenine-DNA glycosylase.

Specific recognition of A/G and A/7,8-dihydro-8-oxoguanine (8-oxoG) mismatches by Escherichia coli MutY: removal of the C-terminal domain preferentially affects A/8-oxoG recognition

Escherichia coli MutY is a 39 kDa adenine DNA glycosylase and 3' apurinic/apyrimidinic (AP) lyase that is active on DNA substrates containing A/G, A/C, or A/8-oxoG mismatches. 8-oxoG (7,8-dihydro-8-oxoguanine or GO) is a major stable product of oxidative damage, and A/GO mismatches may be particularly important biological substrates for MutY. Proteolytic digestion of MutY using thermolysin was found to produce two relatively stable fragments of 25 and 12 kDa. The 25 kDa fragment begins at the N terminus of MutY and spans the region homologous with E. coli endonuclease III, a DNA glycosylase/AP lyase that repairs oxidatively damaged pyrimidines. The 12 kDa fragment, which consists of much of the rest of MutY, had no detectable activity. The purified 25 kDa fragment (M25) had nearly wild-type binding and cleavage activities with A/G-mismatched substrates. Binding to A/GO-mismatched DNA, however, was dramatically reduced in M25 compared to that in intact protein. Borohydride-dependent enzyme-DNA cross-linking, which is a hallmark of the reaction of several DNA glycosylases that possess concomitant AP lyase activity, was also substantially reduced when M25 was allowed to react with A/GO-mismatched DNA. The significant differences in M25 recognition and reactivity with A/G and A/GO mismatches suggest that the C-terminal region of MutY, a region with no homologous counterpart in E. coli endonuclease III, plays an important role in the repair of mismatched DNA arising from oxidation damage.