GN11 Abstracts

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Greener nanomaterial design and synthesis

Green synthesis of inorganic hydroxide clusters as precursors for thin film deposition
Wei Wang1, Shannon W. Boettcher2, and Douglas A. Keszler1, 1Oregon State University, 2University of Oregon
Polynuclear oxo/hydroxo- clusters exhibit unique structures, rich ligand exchange chemistry, and applications across multiple fields, including the life sciences and microelectronics. Highly toxic organic ligands, however, are normally required to produce and stabilize the structure. Moreover, we have found that controlling reaction pathway is critically important for production of a desired product. Here, we present two green approaches for the synthesis of clusters containing Al, Ga, In, and Sc. First, by treating the metal nitrate aqueous/methanol solution with zinc powder, “flat” M13 clusters and a Sc dimer can be realized. Second, electrolysis was used to synthesize Al13 clusters from aqueous solution, which as an alternative offers highly precise pH control. The clusters have been examined as solution precursors for deposition of thin films. The resultant thin films were characterized by several techniques, including TEM, SEM, and electrical measurements.

Untitled
Ryan Atkins, Dave Johnson, Paul Zschack, Michael Anderson
[(SnSe)1.06]m(VSe2)n, [(SnSe)1.16]m(TaSe2)n, and [(SnSe)1.06(VSe2)][(SnSe)1.16(VSe2)] ferecrystals were synthesized using the modulated elemental reactant (MER) technique. The material’s composition, crystal structure, and interdiffusion characteristics were characterized through electron microprobe, x-ray diffraction, and transmission electron microscope analysis. The influence of composition and layering sequence on intergrowth structure and solid diffusion for samples 1<m<6 and 1<n<6 was investigated.

Lead Sulfide Nanoparticles Functionalized with Short-Chain, Ionic, Thiol Ligands: Implications for Stability, Toxicity, and Efficiency in Photonic Devices
Ian Moody, Lisa Truong, Dylan Stankus, Jeff Nason, Robert Tanguay, Mark Lonergan
Semiconductor nanoparticles are of great interest for their size-tunable optical properties and ability to be solution-processed.  These properties make them ideal candidates for low-cost photonic devices (e.g. light-emitting diodes and photovoltaics) and fluorescent biological imaging agents.  Key to these properties is the presence of an organic ligand shell, which coats the surface of the inorganic cores, quenching defect sites and imbuing the nanoparticles with solubility.  However, this ligand-nanoparticle interface is also the weak link in many decomposition processes.  In our studies, we have developed a procedure for preparing lead sulfide nanoparticles (PbS-NPs) functionalized with short-chain, thiol ligands.  These materials can be easily cast into thin film device structures that exhibit efficient photodetection and intriguing electronic transport behavior that is attributed to the ionic nature of the nanoparticle ligand shell.  Additionally, these materials have been assessed in terms of their resistance to precipitation and toxicity in embryonic zebrafish models.  Embryos exposed to PbS-NPs functionalized with a chelating dithiol ligand exhibited less mortality and sub-lethal malformations than those exposed to structurally-analogous, monothiol-functionalized nanoparticles.  The results show how relatively minor changes in surface functionalization can have major implications for the design of  robust nanoparticle systems that are less toxic and more environmentally benign.

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Greener nanomaterial production and manufacturing

Enhanced Photovoltaic Conversion in Dye-Sensitized Solar Cells Utilizing Biological Photonic Crystals
Jeremy Campbell, Greg Rorrer, School of Chemical, Biological and Environmental Engineering, Oregon State University
Diatoms are single-celled photosynthetic organisms that are abundant in marine and freshwater ecosystems. A defining characteristic of these creatures is their production of a silicon dioxide cell wall called a frustule. Diatom frustules possess intricate periodic nanoscale patterning which is precisely genetically controlled and unique to each species. These structures hold promise in applications as natural photonic crystals which can control the flow of light within engineered devices.  Our research focuses on the incorporation of these structures into dye-sensitized solar cells (DSSCs), a promising class of third generation photovoltaic devices based on inexpensive materials and simple fabrication techniques. We have demonstrated that the addition of diatom frustules (31 µg cm-1) to DSSCs results in a 36% improvement in device efficiency, primarily due to increased photocurrent generation. Furthermore, we have developed a novel method for the controlled growth of diatom frustule thin films which have been functionalized to produce DSSCs. Although the current efficiency of these cells is low (>1%), this research demonstrates the feasibility of device fabrication based solely on biological methods.

Comparison studies for synthesis of metal nanoparticles by batch and continuous process.
Sudhir Ramprasad, Patrick E. Ramsing, R. Todd. Miller, Jack T. Rundel, Vincent T. Remcho and Daniel R. Palo
Transition of batchwise nanoparticle production routes to large-scale manufacturing processes is vital for commercialization of such materials. Comparison studies from batch and continuous mode for the synthesis of copper nanoparticles by the polyol method were made. The copper nanoparticles synthesized in continuous mode utilizing a novel microchannel mixer were found to be comparable to the nanoparticles developed in batch mode. Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), and Selected Area Electron Diffraction (SAED) techniques were used for characterization of the copper nanoparticles produced.

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Supercritical Fluids for Advancing Green Nanoparticle Processing
Brad. J Busche, Carlos A. Fernandez, Donnie Clubb, Marvin G. Warner, J. Timothy Bays, R. Shane Addleman

Supercritical fluids (ScF) and nearcritical (NcFs) exhibit many manufacturing advantages compared to conventional wet processing methods.  Many of these compressible fluids are nontoxic, inexpensive, easily removed after processing, and have a density that can be adjusted with pressure or temperature to provide tunable properties such as solubility. The ability to manipulate solubility allows control of the conditions for synthesis, purification, and deposition of nanoparticles.  Factors that affect nanoparticle solubility include the selection of the compressible fluid, the fluid density, stabilizing nanoparticle ligand shell and the nanoparticle size. Understanding and manipulating the dynamic parameters enables development of green processing methods for nanoparticles.

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Advances in nanomaterial characterization

Nanoparticle measurement in a 1m3 emission test chamber.
Michael Wensing, Wolfgang Delius, Ina Kirsch, Tobias Schripp, Tunga Salthamm, Fraunhodfer WKI, Department of Material Analysis and Indoor Chemistry, Braunschweig, Germany

Abstract submitted as an inaccessible, protected pdf file.

Preparation of CdSe nanoparticle films by layer-by-layer assembly for solar cells
Athavan Nadarajah and Rolf Könenkamp, Department of Physics, Portland State University

We report the use of 1,2-ethanedithiol (EDT) as an efficient binding molecule to achieve a smooth and continuous CdSe quantum dot films on deeply nanostructured samples. We combined CdSe semiconductor quantum dots and single-crystal ZnO nanowires to demonstrate a nanowire-quantum-dot heterojunction solar cell. An array of ZnO nanowires were grown electrochemically on a transparent conducting glass (FTO) substrate in aqueous solutions of KCl, ZnCl2, and AlCl3 at 80oC. The FTO substrate was coated with a compact planar ZnO thin film by spray pyrolysis prior to ZnO nanowire growth. The resulting ZnO nanowires were coated with an absorber layer of CdSe quantum dots by a layer-by-layer dip-coating that utilizes 1,2-ethanedithiol (EDT) in acetonitrile as a solvent to remove the initial electrically insulating capping ligand molecule. A p-layer was applied to sandwich the CdSe quantum dot film between a p-n junction of n-type ZnO nanowires and a hole conducting material. The back contact is a thermally evaporated Au layer. This design could offer new and enhanced opportunities to harvest light energy in the whole visible region of solar light. Previously, we have investigated number of variations of solar cell design. These included cells created with different p-type layers, with or without application of a compact ZnO thin film prior to ZnO electrodeposition, and using various durations of CdSe quantum dot layer annealing. We have also reported a power-conversion efficiency above 2 % with a short-circuit photocurrent density (Jsc) of 10 mA/cm2 and an opencircuit voltage (Voc) of 0.40 V for the well-annealed ZnO thin film/ZnO nanowires/CdSe/P3HT nanostructure [1]. Our recent ZnO based heterojunction solar cells were prepared by a layer by-layer dip-coating of CdSe quantum dots that utilizes 1.2-ethanedithiol (EDT) as a binding agent to improve the electronic coupling of nanoparticles by removing the electrically insulating ligand molecules originally capping the nanoparticles. We find that the photoresponse increases noticeably with EDT treatment of the nanoparticles surface, which causes the photo-response spectrum onset position to shift in energy towards the CdSe quantum dot bandgap value. The CdSe nanoparticles treated with EDT followed by surfactant-aided thermal annealing further increases the quantum efficiency. The surfactant-aided thermal annealing produces a CdSe continuous polycrystalline film in which carrier confinement effects are no longer active; this efficiently promotes the separation of photogenerated carriers. The combination of EDT treatment of CdSe nanoparticles surface followed by surfactant-aided thermal annealing play an important role in improving the solar cells’ performance, resulting in a maximum external quantum efficiency of 40% in the visible spectral range.
Reference:
[1] Athavan Nadarajah, Robert C. Word, and Rolf Koenenkamp, Mater. Res. Soc. Symp. Proc., 1178, 2009.

Directed assembly, characterization and manipulation of nanoparticle arrays on surfaces.
Edward W. Elliott III, Richard D. Glover, and Beverly L. Smith

Both the scale and dynamic nature of nanomaterials creates several characterization challenges when investigating transformations. By using a novel platform that allows for both the direct visualization and manipulation of nanoparticle arrays, many of these challenges are addressed. Functionalized TEM Smart grids are utilized for both directed assembly and characterization of nanoparticle arrays both before and after manipulation. Investigations have probed changes in the system due to thermal and chemical treatments. By monitoring nanoparticle arrays over the course of thermal treatments we have gained a greater understanding of the mechanism of nanoparticle growth on solid surfaces. Carefully tuned oxidative treatments afford the partial removal and modification of the ligand shell without compromising the integrity of the nanoparticle arrays. Taken together these investigations have provided insight into dynamic nanoparticle behaviors on surfaces, which will inform improved design of future nanomaterials with enhanced functionality.

Utilization of SAXS to Characterize Nanoparticles in Real Time and Perform Kinetic Measurements in a Continuous-flow Microreactor
Patrick Haben, Edward Elliott, Samuel Lohse, Erik Richman

As we seek to better understand and control nanoparticle formation reactions it has become increasingly important to access real-time information for these materials.  The use of a continuous-flow microreactor platform has enabled simultaneous in situ small-angle X-ray scattering (SAXS) and UV-visible characterization of reacting Au nanoparticle (AuNP) solutions. The microfluidic reactor allows us to view various reaction times for extended durations via these combined characterization techniques, which provide quantitative size distribution information coupled with rapidly collected optical spectra. Utilizing HAuCl4 as a Au source, mercapto-ethoxy-ethoxy-ethanol Bunte Salt (MEEE) as a passivating ligand and NaBH4 as reducing agent, we have observed AuNP formation and growth between 3- and 60-second residence times for two Au concentrations.  Combination of our real-time microfluidic characterization method with a recently acquired lab-scale SAXS instrument presents us with the ability to rapidly assess the influence of various reaction parameters (i.e., ligand and reductant concentration) on this system in addition to myriad other nanoparticle systems.

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Impacts and distribution in living systems and the environment

THE USE OF GREEN NANOTECHNOLOGY FOR DEVELOPMENT OF NOVEL DRUG DELIVERY SYSTEMS IN MEDICINE
Georgy Mikhaylov1, Ursa Mikac2, Anna A. Magaeva3, Volya I. Itin3, Thomas Reinheckel4, Christoph Peters4, Matthew Bogyo5, Sergej G. Psakhye3, Boris Turk1, Olga Vasiljeva1
1Department of Biochemistry and Molecular and Structural Biology, J. Stefan Institute, Ljubljana, Slovenia; 2Department of Condensed Matter Physics, J. Stefan Institute, Ljubljana, Slovenia,; 3Tomsk Scientific Center, Siberian Branch of Russian Academy of Sciences, Tomsk, Russia; 4Institut für Molekulare Medizin und Zellforschung, Albert-Ludwigs-Universität Freiburg, Germany, 5Department of Pathology, Microbiology and Immunology, Stanford University School of Medicine, USA.

Researchers from around the world are actively integrating nanotechnology into the treatment of various diseases that influence human health. The development of new safe and effective drug delivery systems for treatment of cancer is one of the top priority trends in the biomedical technology of the last decade. Among the different methods of drug delivery, magnetic drug targeting could be a promising approach by possibility of specific delivery of chemotherapeutic agents using magnetic nanoparticles and an external magnetic field. In the present study we aimed to develop a novel superparamagnetic nanoparticles based delivery system that could improve patient compliance and enhance safety and efficacy of cancer treatment.  Combining novel physical, chemical and bio-medical approaches we have developed and tested methods for preparing ferrimagnetic nanoparticles encapsulated in biocompatible lipid vesicles. Nanomaterial-biological interactions have been investigated at multiple levels of biological organization: from cellular to organismal; thus providing the key data to ensure the quality and safety of the developed delivery system employing green nanotechnology. Finally, a successful pre-clinical trial has confirmed the efficiency of the developed system in vivo. These data provided evidence that the developed magnet-sensitive lipidated nano-carrier appears to be a valuable and bio-safe drug delivery system that has a major potential for use in tumor diagnosis and treatment.

Aerosolized ZnO nanoparticles impose toxicity in alveolar type II epithelial cells at the air-liquid interface
Yumei Xie1, Nolann Williams1, Ana Tolic1, William Chrisler1, Justin Teeguarden1, Bettye Maddux2, Joel Pounds1, Alexander Laskin1 & Galya Orr1
1. Pacific Northwest National Laboratory, Richland, Washington; 2. University of Oregon, Eugene, Oregon

To date, the majority of in vitro studies characterizing the impact of engineered nanoparticles (NPs) on cells that line the respiratory tract have been carried out in cells exposed to NPs in solution. To more closely mimic in vivo exposures to airborne NPs, which are likely to be deposited in the alveolar region, we established the exposure of alveolar type II epithelial cells (C10 cell line) to aerosolized NPs at the air-liquid interface (ALI). This approach is especially important when assessing NPs that tend to agglomerate or are dissolved in solution, such as ZnO NPs. The cells are cultured on membrane inserts and exposed to ambient air at their apical surface when they reach confluence. Exposures to aerosolized NPs, generated by a vibrating membrane nebulizer and carried over the cells using humidified air-flow through the enclosed exposure chambers, are conducted over 10-20 min sessions. Precise exposure doses are quantified as the number of settled particles per unit area (or particles per cell) by collecting the particles on millimeter-size grids, placed randomly over the cells and visualized using electron microscopy.  Using this approach we find that aerosolized ZnO NPs (forming aggregates with 117 nm median diameter) become toxic to the cells at about 500 aggregates per cell (20 µm2), as assessed 24 hrs post exposure by quantifying LDH release, proliferation (MTS) and cell death (PI). Cells grown on the same membranes but exposed to ZnO NPs when submersed under growth media, elicit a toxic response at about 300 aggregates per cell, as assessed 24 hrs post exposure. Cells exposed at the ALI to aerosolized droplets generated from the supernatant alone, after removing the NPs by ultracentrifugation, do not elicit toxic response even when taken from high particle concentrations. Using flowcytometry to assess oxidative stress in cells exposed to aerosolized NPs at the ALI we find a clear increase in ROS generation that reaches maximum at 6 hrs post exposure.  Together, these observations indicate that airborne ZnO NPs induce toxicity that must originate from processes occurring at the site of particle contact with cellular structures, either by direct interactions with the intact NP or with locally (nm scale) dissolved Zn2+, and these processes elicit ROS generation as early as 4 hrs after the aerosolized particles land on the cell surface. The larger number of particles needed to elicit toxicity by airborne ZnO NPs, when compared with particles in solution, can be explained by the local processes at the contact site, rather than the massive and global dissolution that occurs when ZnO NP toxicity is assessed in solution.

A Novel Approach to Assess Nanomaterial Impacts on Aquatic Ecosystems: ‘Nanocosms’.
Cassandra Viéville1*and Stacey L. Harper1,2 , 1-Chemical, Biological and Environmental Engineering, 2-Environmental and Molecular Toxicology

Recent developments in the field of nanotechnology have led to exponential growth in the exploitation of nanomaterials.  While applications of nanomaterials are ever increasing, little information is available on toxicity and environmental impact of these nanomaterials.  Current methods for assessing nanomaterial toxicity are limited when applied to nanomaterials.  Here, we illustrate the utility of ‘nanocosms’ to rapidly determine the toxic potential and environmental impacts of nanomaterials on aquatic ecosystems.  ‘Nanocosms’ are comprised of multiple trophic levels (i.e. algae, ciliate, bacteria) and designed to simulate aquatic ecosystems at significantly reduced volumes.   Preliminary investigations indicate that ‘nanocosms’ are stable, reproducible, demonstrate typical predator-prey interactions, and are responsive to toxic insult.  Acute validation exposures to CuSO4 and AgNO3 (0ppm, 10ppm, 100ppm) resulted in a typical toxicological concentration-response.  Additional investigations have included acute exposures to <50nm yttrium oxide nanoparticles (Y203 NPs) in the presence and absence of dissolved organic matter (DOM).  The presence of DOM altered the impact to organisms differently. Some organisms became more sensitive to Y203 NPs in the presence of DOM.    We believe the development and standardization of ‘nanocosms’ will provide a rapid method to assess nanoparticle behavior within a controlled simulated ecosystem.

Evaluating the Toxicological Response of Peptide-Based Nanochelators Using the Zebrafish Model
Federico Sinche, Marilyn R. Mackiewicz, Stacey Harper

At the forefront of nanotechnology development is the design of innocuous nanomaterials which revolves around the use of biocompatible metals as well as stabilizing ligands.  Plant-based cysteine-rich peptides are of significant interest as these can serve as stabilizing ligands as well as chelating ligands that bind to exogenous heavy metal ions.  Natural phytochelatin (PC) cysteine-rich peptides found in certain plants have extremely high metal uptake, tolerance, and specificity and, thus, have the potential to serve as chelating and stabilizing ligands. A new class of gold-based nanochelators with these PC peptides has been developed. These materials have multi-modal functionalities such that they can serve as chelating agents, imaging sensors and can be used in metal recovery.  Each nanoparticle has thousands of these ligands on the surface with oxygen, nitrogen, and sulfur donor ligands that are available for binding and stabilization of metals with different oxidation state and coordination geometries. The synthetic methodology for the preparation of this new class of nanochelators with PC peptides will be presented along with UV-vis, TEM and dynamic light scattering measurements.   Since these materials will be used for bioimaging and chelation therapy in humans, it is equally important to evaluate for potential acute toxic effects. In this respect, the use of the zebrafish model has been used successfully as a rapid screening method to detect potential levels of toxicity from over 200 nanomaterials.  Preliminary results from the zebrafish assays show low levels of toxicity for nominal concentrations higher than 25 ppm for gold-based nanochelators surface functionalized with tripeptide and pentapeptide PC derivatives.  This platform of nanochelators with corresponding low toxicity presents a new class of materials that could be used for many biological applications.

The influence of divalent cations and Suwannee River Humic Acids on silver ion and silver nanoparticle toxicity on the ammonia oxidizing bacterium, Nitrosomonas europaea.
Tyler S. Radniecki, Dylan P. Stankus, Joseph W. Anderson, Margaret C. Schneider, Jeffrey A. Nason and Lewis Semprini; School of Chemical, Biological and Environmental Engineering, Oregon State University, 102 Gleeson Hall, Corvallis, OR 97331

The use of silver nanoparticles (Ag-NP) as a broad spectrum biocide in a wide range of consumer goods has grown exponentially since 2006.  Many of these consumer goods have been shown to release their Ag-NP content which will result in an increased release of Ag-NP into wastewater treatment plant (WWTP) influent and ultimately the WWTP receiving bodies of water.  Ammonia oxidizing bacteria (AOB) play a critical role in the removal of nitrogen during wastewater treatment through the oxidation of ammonia (NH3) to nitrite (NO2-) and are widely considered to be the most sensitive fauna in WWTPs.  This research examines how various aqueous chemistries influences the nitrification inhibition of Nitrosomonas europaea, the model AOB, by silver ions (Ag+) and citrate-stabilized BioPure 20 nm Ag-NP (nanoComposix, Inc., San Diego, CA).  The presence of divalent cations reduced Ag-NP toxicity by inducing aggregation of the Ag-NP suspensions and thus reduced their Ag+ dissolution rates.  Additionally, the presence of divalent cations reduced Ag+ toxicity through possible competition for binding sites on or transport within the cells.  The presence of Suwannee River Humic Acids stabilized Ag-NP suspensions in the presence of divalent cations but reduced toxicity even further through an increased drop in Ag+ dissolution rates.

Multi-modal toxicology and biohazard assessment of nanomaterial-based thin films
Navin K. Verma1,2*, Jennifer Conroy1*, Philip Lyons2, Jonathan Coleman2, Mary O’Sullivan1, Hardy Kornfeld3, Dermot Kelleher1, and Yuri Volkov1,2; 1Institute of Molecular Medicine, Trinity College Dublin, Ireland; 2Centre for Research on Adaptive Nanostructures & Nanodevices, Trinity College Dublin, Ireland; 3University of Massachusetts Medical School, Worcester, Massachusetts   *Equal contribution

Nanomaterials and their enabled products are increasingly attracting global attention due to their unique physicochemical properties. However, because of the raising health and safety concerns, nano-products require a rigorous biocompatibility assessment. Here, we analyzed the biocompatibility of silver nanowire-based transparent and flexible thin films. Based on confocal and atomic force microscopic analysis of cellular adhesion, morphology and topology of cultured human phagocytic cells THP1 grown on these films, they were found to be biocompatible. Due to the fact that components of nanomaterial-based products may come in contact with humans during handling, manufacture, use, and disposal with the increased possibility of them causing adverse health impact, we analyzed the biocompatibility of silver nanowires. Four cell lines including human epithelial, endothelial, gastric, and phagocytic cells were exposed to varying length (3-6 µm) silver nanowires (0.1-5 µg/ml). Confocal microscopic examination confirmed the possibility of intracellular accumulation of silver nanowires. Utilizing a high content screening system in combination with real-time impedance sensing, we observed a low but cell-type-, nanowire length-, dose- and incubation time-dependent cytotoxicity of silver nanowires. Our results emphasise the necessity of robust experimental procedures and multi-modal biohazard assessment of products incorporating nanomaterials.

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A new lens for monitoring nanomaterial fate and evolution.
John M. Miller, Richard Glover, James Hutchison, University of Oregon

A fundamental challenge in assessing the safety of nanotechnology has been the collective inability of the scientific community to accurately determine the fate and evolution of nanomaterials. For example, nanosilver has been actively studied due to its widespread presence as an antimicrobial agent in a large number of consumer products. However, the vast majority of these studies indirectly monitor the behavior of these particles (ions released or total silver content).    In this presentation, we report the use of a novel analysis strategy that enables, for the first time, the ability to capture and directly monitor the reactivity and transformations of nanomaterials under a wide range of conditions. This approach revealed the surprising discovery that all silver nanoparticles (AgNPs) exhibit dynamic behavior when deposited on surfaces. In the presence of humidity, large numbers of smaller Ag NPs form in the vicinity of deposited particles within hours, yet Ag NPs in solution remain stable for many months. Similar behavior was observed for a range of particle sizes (10 nm, 20 nm, and 75 nm) and stabilizers (polyvinylpyrrolidone (PVP), citrate, and polysorbate-20). These findings challenge conventional thinking about nanoparticle stability and how these particles behave in products over their lifetime.

Platform sessions

Session I: Addressing reproducibility in nanomaterial synthesis

Observing Environmental Transformations to Nanomaterials Using a Novel Characterization Platform, Richard Glover

Nanomaterials are increasingly incorporated into consumer products bringing concern over how to utilize them while still protecting human and environmental health.  Due to the complexity and unknown reactivity of nanomaterials there is uncertainty over what side products and interactions to monitor.  Often, the methods employed will indirectly monitor or attempt to recover these materials.  This process can be destructive and results are often incomplete, inconclusive, or misleading.  In order to better understand nanomaterial transformations we assembled nanoparticles on an electron transparent substrate.  With 2-D monolayers of these materials we can directly monitor particles, before and after the material is exposed to various environmental conditions.  Using high resolution characterization techniques like TEM, XPS, and AFM the physical and chemical transformations can be measured and quantified.  Our approach has enabled the observation of some new and fundamentally interesting behavior of silver and gold nanoparticles.

Session II. Advances and challenges in exploring the nano/bio interface

Multi-modal toxicology and biohazard assessment of nanomaterial-based thin films
Navin K. Verma1,2*, Jennifer Conroy1*, Philip Lyons2, Jonathan Coleman2, Mary O’Sullivan1, Hardy Kornfeld3, Dermot Kelleher1, and Yuri Volkov1,2

1Institute of Molecular Medicine, Trinity College Dublin, Ireland; 2Centre for Research on Adaptive Nanostructures & Nanodevices, Trinity College Dublin, Ireland; 3University of Massachusetts Medical School, Worcester, Massachusetts   *Equal contribution

Nanomaterials and their enabled products are increasingly attracting global attention due to their unique physicochemical properties. However, because of the raising health and safety concerns, nano-products require a rigorous biocompatibility assessment. Here, we analyzed the biocompatibility of silver nanowire-based transparent and flexible thin films. Based on confocal and atomic force microscopic analysis of cellular adhesion, morphology and topology of cultured human phagocytic cells THP1 grown on these films, they were found to be biocompatible. Due to the fact that components of nanomaterial-based products may come in contact with humans during handling, manufacture, use, and disposal with the increased possibility of them causing adverse health impact, we analyzed the biocompatibility of silver nanowires. Four cell lines including human epithelial, endothelial, gastric, and phagocytic cells were exposed to varying length (3-6 µm) silver nanowires (0.1-5 µg/ml). Confocal microscopic examination confirmed the possibility of intracellular accumulation of silver nanowires. Utilizing a high content screening system in combination with real-time impedance sensing, we observed a low but cell-type-, nanowire length-, dose- and incubation time-dependent cytotoxicity of silver nanowires. Our results emphasise the necessity of robust experimental procedures and multi-modal biohazard assessment of products incorporating nanomaterials.

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