Stephan Wagner

Release of TiO2 nanoparticles from sunscreens into surface waters: a one-year survey at the old Danube recreational Lake.

Monitoring data are necessary for the future production of engineered nanomaterials and the development of regulations for nanomaterials. Therefore, it is necessary to develop methods that reliably detect and quantify nanomaterials in real-world systems at expectedly low concentrations. In this work we tested several methodological approaches to detect titanium dioxide nanomaterials released from sunscreen products into the Old Danube Lake (Vienna, Austria), which is heavily used for recreational activities like bathing and water sports during the summer season. During a 12-month period suspended particulate matter (SPM) was collected from the lake and analyzed using a combination of complementary techniques. By sampling at a location approximately 50 m from the nearest bathing area and at one meter depth from the water surface, we focused on the potentially mobile fraction of the released nanoparticles. We were able to identify titanium dioxide nanoparticles stemming from sunscreens in the suspended matter of the lake using electron microscopy. Bulk analysis of SPM clearly shows an increase of Ti-containing particles during the summer season. These analyses, however, are not able to distinguish sunscreen nanoparticles from natural Ti-bearing nanoparticles. Therefore, Elemental ratios of Ti with Al, V, Ga, Y, Nb, Eu, Ho, Er, Tm, Yb, and Ta as determined by ICPMS and ICPOES, in combination with single particle ICPMS analysis were applied to establish local background values. The observed mild increase of Ti elemental ratios, compared to spring background values indicates that the residence time of released nanomaterials in the water column is rather short. Overall, the advantages and disadvantages of the methods used to detect and characterize the nanomaterials are discussed.

Optimization and evaluation of asymmetric flow field-flow fractionation of silver nanoparticles

Asymmetric flow field-flow fractionation (AF(4)) in combination with on-line optical detection and mass spectrometry is one of the most promising methods for separation and quantification of nanoparticles (NPs) in complex matrices including food. However, to obtain meaningful results regarding especially the NP size distribution a number of parameters influencing the separation need to be optimized. This paper describes the development of a separation method for polyvinylpyrrolidone-stabilized silver nanoparticles (AgNPs) in aqueous suspension. Carrier liquid composition, membrane material, cross flow rate and spacer height were shown to have a significant influence on the recoveries and retention times of the nanoparticles. Focus time and focus flow rate were optimized with regard to minimum elution of AgNPs in the void volume. The developed method was successfully tested for injected masses of AgNPs from 0.2 to 5.0 μg. The on-line combination of AF(4) with detection methods including ICP-MS, light absorbance and light scattering was helpful because each detector provided different types of information about the eluting NP fraction. Differences in the time-resolved appearance of the signals obtained by the three detection methods were explained based on the physical origin of the signal. Two different approaches for conversion of retention times of AgNPs to their corresponding sizes and size distributions were tested and compared, namely size calibration with polystyrene nanoparticles (PSNPs) and calculations of size based on AF(4) theory. Fraction collection followed by transmission electron microscopy was performed to confirm the obtained size distributions and to obtain further information regarding the AgNP shape. Characteristics of the absorbance spectra were used to confirm the presence of non-spherical AgNP.

Alterations of ΔTA‐p 73 splice transcripts during melanoma development and progression

In the last 2 years, it has become apparent that the p53‐family members p53 and p73 play fundamentally different roles in human malignancies. In contrast to p53, many studies on cancer patients failed to detect mutational inactivation of p73 and reported overexpression of wild‐type p73 instead. A possible explanation was provided by the recent discovery of N‐terminal truncated isoforms of p73 (ΔTA‐p73) that act as dominant‐negative inhibitors of wild‐type p53 and TA‐p73 and result in tumor growth in nude mice. We investigated the role of ΔTA‐p73 in the development and progression of human melanomas, which lack p53 mutations. We analyzed 8 benign melanocytic nevi, 8 primary melanomas and 19 melanoma metastases for alterations of TA‐p73 and ΔTA‐p73 expression using isoform‐specific real‐time RT‐PCR. Based on our results, p73Δex2 and Δex2/3 spliced transcripts derived from the first promoter were significantly up‐regulated in melanoma metastases, whereas ΔN‐p73 generated from the second promoter was the predominant isoform in benign nevi. Moreover, increased expression of p73Δex2 and p73Δex2/3 correlated with high‐levels of both TA‐p73 and E2F1. Our data suggest a potential function of ΔTA‐p73 splice isoforms in melanoma progression.

First steps towards a generic sample preparation scheme for inorganic engineered nanoparticles in a complex matrix for detection, characterization, and quantification by asymmetric flow-field flow fractionation coupled to multi-angle light scattering and ICP-MS

The applicability of a multi-step generic procedure to systematically develop sample preparation methods for the detection, characterization, and quantification of inorganic engineered nanoparticles (ENPs) in a complex matrix was successfully demonstrated. The research focused on the optimization of the sample preparation, aiming to achieve a complete separation of ENPs from a complex matrix without altering the ENP size distribution and with minimal loss of ENPs. The separated ENPs were detected and further characterized in terms of particle size distribution and quantified in terms of elemental mass content by asymmetric flow-field flow fractionation coupled to a multi-angle light scattering detector and an inductively coupled plasma mass spectrometer. Following the proposed generic procedure SiO2-ENPs were separated from a tomato soup. Two potential sample preparation methods were tested these being acid digestion and colloidal extraction. With the developed method a complete SiO2-ENPs and matrix separation with a Si mass recovery >90% was achieved by acid digestion. The alteration of the particle size distribution was minimized by particle stabilization. The generic procedure which also provides quality criteria for method development is urgently needed for standardized and systematic development of procedures for separation of ENPs from a complex matrix. The chosen analytical technique was shown to be suitable for detecting SiO2-ENPs in a complex food matrix like tomato soup and may therefore be extended to monitor the existence of ENPs during production and safety control of foodstuffs, food labelling, and compliance with legislative limits.

Production of reference materials for the detection and size determination of silica nanoparticles in tomato soup.

A set of four reference materials for the detection and quantification of silica nanoparticles (NPs) in food was produced as a proof of principle exercise. Neat silica suspensions were ampouled, tested for homogeneity and stability, and characterized for total silica content as well as particle diameter by dynamic light scattering (DLS), electron microscopy (EM), gas-phase electrophoretic molecular mobility analysis (GEMMA), and field-flow fractionation coupled with an inductively coupled mass spectrometer (FFF-ICPMS). Tomato soup was prepared from ingredients free of engineered nanoparticles and was spiked at two concentration levels with the silica NP suspension. Homogeneity of these materials was found sufficient to act as reference materials and the materials are sufficiently stable to allow long-term storage and distribution at ambient temperature, providing proof of principle of the feasibility of producing liquid food reference materials for the detection of nanoparticles. The spiked soups were characterized for particle diameter by EM and FFF-ICPMS (one material only), as well as for the total silica content. Although questions regarding the trueness of the results from EM and FFF-ICPMS procedures remain, the data obtained indicate that even assigning values should eventually be feasible. The materials can therefore be regarded as the first step towards certified reference materials for silica nanoparticles in a food matrix.

Microplastic Exposure Assessment in Aquatic Environments: Learning from Similarities and Differences to Engineered Nanoparticles

Microplastics (MPs) have been identified as contaminants of emerging concern in aquatic environments and research into their behavior and fate has been sharply increasing in recent years. Nevertheless, significant gaps remain in our understanding of several crucial aspects of MP exposure and risk assessment, including the quantification of emissions, dominant fate processes, types of analytical tools required for characterization and monitoring, and adequate laboratory protocols for analysis and hazard testing. This Feature aims at identifying transferrable knowledge and experience from engineered nanoparticle (ENP) exposure assessment. This is achieved by comparing ENP and MPs based on their similarities as particulate contaminants, whereas critically discussing specific differences. We also highlight the most pressing research priorities to support an efficient development of tools and methods for MPs environmental risk assessment.

Silver and gold nanoparticle separation using asymmetrical flow-field flow fractionation: Influence of run conditions and of particle and membrane charges

Flow-Field Flow Fractionation (Flow-FFF), coupled with online detection systems is one of the most promising tools available for the separation and quantification of engineered nanoparticles (ENPs) in complex matrices. To correctly relate the retention of nanoparticles in the Flow-FFF-channel to the particle size, ideal separation conditions must be met. This requires optimization of the parameters that influence the separation behavior. The aim of this study was therefore to systematically investigate and evaluate the influence of parameters such as the carrier liquid, the cross flow, and the membrane material, on the separation behavior of two metallic ENPs. For this purpose the retention, recovery, and separation efficiency of sterically stabilized silver nanoparticles (AgNPs) and electrostatically stabilized gold nanoparticles (AuNPs), which represent two materials widely used in investigations on environmental fate and ecotoxicology, were investigated against a parameter matrix of three different cross-flow densities, four representative carrier solutions, and two membrane materials. The use of a complex mixture of buffers, ionic and non-ionic surfactants (FL-70 solution) together with a medium cross-flow density provided an acceptable compromise in peak quality and recovery for both types of ENPs. However, these separation conditions do not represent a perfect match for both particle types at the same time (maximized recovery at maximized retention). It could be shown that the behavior of particles within Flow-FFF channels cannot be predicted or explained purely in terms of electrostatic interactions. Particles were irreversibly lost under conditions where the measured zeta potentials suggested that there should have been sufficient electrostatic repulsion to ensure stabilization of the particles in the Flow-FFF channel resulting in good recoveries. The wide variations that we observed in ENP behavior under different conditions, together with the different behavior that has been reported in published literature for the same NPs under similar conditions, indicate a need for improvement in the membrane materials used for Flow-FFF analysis of NPs. This research has shown that careful adjustment of separation conditions can result in acceptable, but not ideal, separation conditions for two fundamentally different stabilized materials, and that it may not be possible to separate a set of different particles under ideal conditions for each particle type. This therefore needs to be taking into account in method development and when interpreting FFF results from complex samples.

EMCCD technology and its impact on rapid low-light photometry

Electron Multiplying Charge Coupled Devices (EMCCDs) are CCD cameras with potentially single-photon detection ability. Signal amplification is achieved by way of a unique electron-multiplying structure built into the silicon, and the gain can be varied in order to overcome the read-noise floor, which is the usual limiting factor in reading out a conventional CCD at high frame rates. In combination with its high quantum efficiencies, the EMCCD holds great promise for time-resolved photometry. We report here results from two observing campaigns aimed at assessing the suitability of EMCCD technology for detecting short-timescale, low-amplitude variability in blazars. Data were taken on the 2.2m telescope at Calar Alto using both front-illuminated and back-illuminated EMCCD cameras from Andor Technology’s iXon range. Approximately 410,000 science frames were recorded over 10 nights. The results presented here illustrate the photometric stability achieved with the cameras, under typical observing conditions. In general, photometric precision down to the level of a few millimagnitudes is found to be possible. We argue that reliable photometry is best achieved with high data collection rates (typically 4 frames per second) coupled to ultra-low-noise detectors such as the EMCCD.

Nanoparticles in the environment: where do we come from, where do we go to?

Nanoparticles serve various industrial and domestic purposes which is reflected in their steadily increasing production volume. This economic success comes along with their presence in the environment and the risk of potentially adverse effects in natural systems. Over the last decade, substantial progress regarding the understanding of sources, fate, and effects of nanoparticles has been made. Predictions of environmental concentrations based on modelling approaches could recently be confirmed by measured concentrations in the field. Nonetheless, analytical techniques are, as covered elsewhere, still under development to more efficiently and reliably characterize and quantify nanoparticles, as well as to detect them in complex environmental matrixes. Simultaneously, the effects of nanoparticles on aquatic and terrestrial systems have received increasing attention. While the debate on the relevance of nanoparticle-released metal ions for their toxicity is still ongoing, it is a re-occurring phenomenon that inert nanoparticles are able to interact with biota through physical pathways such as biological surface coating. This among others interferes with the growth and behaviour of exposed organisms. Moreover, co-occurring contaminants interact with nanoparticles. There is multiple evidence suggesting nanoparticles as a sink for organic and inorganic co-contaminants. On the other hand, in the presence of nanoparticles, repeatedly an elevated effect on the test species induced by the co-contaminants has been reported. In this paper, we highlight recent achievements in the field of nano-ecotoxicology in both aquatic and terrestrial systems but also refer to substantial gaps that require further attention in the future.

Tire wear particles in the aquatic environment - A review on generation, analysis, occurrence, fate and effects

Tire wear particles (TWP), generated from tire material during use on roads have gained increasing attention as part of organic particulate contaminants, such as microplastic, in aquatic environments. The available information on properties and generation of TWP, analytical techniques to determine TWP, emissions, occurrence and behavior and ecotoxicological effects of TWP are reviewed with a focus on surface water as a potential receptor. TWP emissions are traffic related and contribute 5-30% to non-exhaust emissions from traffic. The mass of TWP generated is estimated at 1,327,000 t/a for the European Union, 1,120,000 t/a for the United States and 133,000 t/a for Germany. For Germany, this is equivalent to four times the amount of pesticides used. The mass of TWP ultimately entering the aquatic environment strongly depends on the extent of collection and treatment of road runoff, which is highly variable. For the German highways it is estimated that up to 11,000 t/a of TWP reach surface waters. Data on TWP concentrations in the environment, including surface waters are fragmentary, which is also due to the lack of suitable analytical methods for their determination. Information on TWP properties such as density and size distribution are missing; this hampers assessing the fate of TWP in the aquatic environment. Effects in the aquatic environment may stem from TWP itself or from compounds released from TWP. It is concluded that reliable knowledge on transport mechanism to surface waters, concentrations in surface waters and sediments, effects of aging, environmental half-lives of TWP as well as effects on aquatic organisms are missing. These aspects need to be addressed to allow for the assessment of risk of TWP in an aquatic environment.