Fate, Transport, and Toxicity of Nanoparticles in the Environment Steven J. OIdenburg, Thomas K. Darlington nanocomposix, Inc., San Diego, CA Tonya Savage and Mitch Bogle AFOSR, Eglin AFB, FL
Talk Outline Nanotechnology and Nanotoxicology Challenges of Nanotoxicology Research Nanoparticles for Environmental Studies Transport of Benchmark Nanoparticles Transport of Aluminum Nanoparticles
Nanotechnology Research and technology development at the atomic, molecular, or macromolecular levels using a length scale of 1-100 nanometers in any dimension. EPA Nanotechnology White Paper February 2007
Risks Associated with Nanotechnology Nanotechnology has emerged as a growing and rapidly changing field. New generations of nanomaterials will evolve, and with them new and possibly unforeseen environmental issues. EPA White Paper on Nanotechnology February 2007
Environmental Nanotoxicology Determine the impact of manufactured nanomaterials on the environment Monitor the fate and transport of nanoparticles in soil, water, and the atmosphere Understand the effect of nanoparticles on plants, micro-organisms, and aquatic species Once hazards have been identified, propose remediation techniques that will minimize environmental impact
Challenges #1: Size, Shape and Surface Dependent Properties Nanostructures of zinc oxide Wang ZL, Materials Today, June 2004 p.27-33
Challenges #2: Size Dependent Toxicity 20 nm diameter TiO 2 particles have a much greater pulmonary toxicity than pigment-grade TiO 2 particles (>10X larger) with the same composition (Bermudez, E., et al., Toxicol. Sci. (2004) 77, 347) Individual 26 nm diameter polytetrafluoroethene (PTFE) particles are toxic to rats as individual but not as agglomerated particles. (Oberdörster, G., et al., Inhal. Toxicol. (1995) 7, 111) Multi-walled carbon nanotubes are more proinflammatory when compared to ultrafine carbon black particles on an equivalent mass dose metric. (Shvedova et al. Am. J. Physiol. Lung Cell Mol. Physiol. (2005) 289, L698)
Challenges #3: Aggregation Dependent Properties 2000 nanoparticles dispersed (diameter = 10 nm) 2000 nanoparticles aggregated (aggregate size = 100 nm)
Initial Study Goals Understand transport of aluminum nanoparticles in sand and soil. Study nanoparticle benchmark particles with monodisperse sizes and well defined surface chemistry. Compare benchmark particle transport to aluminum nanoparticle transport (aggregated nanoparticles with a dynamic surface chemistry). Measure nanoparticle induced toxicity in plants and aquatic species
Gold and silver nanoparticle benchmark materials Well controlled size and shape Colorimetric aggregation signature Surface chemistry can be easily modified ICP can trace to PPB level Gold is non-toxic, silver is toxic
Nanoparticle Characterization: Dark Field Microscopy & Plasmon Resonance The optical properties of gold and silver change dramatically when the dimensions of the material are reduced below 100 nm. From Kelly et. al, J. Phys. Chem B, 107, 668.
Nanoparticle Characterization: Dark Field Microscopy 80 nm Gold Colloid 60 nm Silver Colloid
Nanoparticle Characterization: Dark Field Microscopy Dark field images of (a) 80 nm diameter gold particles (b) soil sample (c) gold nanoparticles and soil samples mixed.
Soil Analysis After Transport 40 nm Gold nanoparticles interact with specific soil components
Nanoparticle Transport Experimental Setup Syringe pump delivery of particles and precise flow rate Glass column to hold transport matrix In line flow cell detection with HP8453 UV-Vis
Transport of 19 nm Gold in Sand 1.2 1 0.8 C/C0 0.6 0.4 0.2 0 0 1 2 3 4 5 Pore Volumes Sample 1 Sample 2 Sample 3 Sample 4 Tracer Dye Nanoparticle flow through a 7 cm sand (60 mesh) column loaded with 3.9 g of sand at a rate of 0.05 ml / minute.
Transport of Gold Particles in Sand 1.2 1.0 0.8 C/Co 0.6 0.4 0.2 4 nm Gold (THPC) 19 nm (Citrate) 43 nm (KCarbonate) 86 nm (KCarbonate) 190 nm (Citrate) 0.0 0 2 4 6 8 10 12 14 16 Pore Volumes Nanoparticle flow through a 7 cm sand (60 mesh) column loaded with 3.9 g of sand at a rate of 0.05 ml / minute.
Transport of Gold Particles in Soil C/C0 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.0 5.0 10.0 Volume (ml) 19 nm citrate stabilized gold nanoparticles flowing through a 7 cm soil column (Eglin AFB soil sample).
Transport of Gold Nanoparticles in Sand Low affinity of gold particles for sand: consistent with negative surface charge of both sand and gold No effect of size on particle mobility in the range tested (4-190 nm) Surface properties determine transport characteristics Gold nanoparticles interact with soil components.
Bulk Aluminum Toxicity Aluminum in bulk form is generally regarded as safe: Oral little toxicity on the order of grams Dermal minimal Inhalation on the order of nuisance dust Systemic suggested link with Alzheimer's Disease
Nanoaluminum Toxicity Toxicity of nanoaluminum is under investigation: Nanoaluminum readily internalized into cell lysosomes Evidence that unreacted nanoaluminum is more toxic than aluminum oxide (in-vitro model A549 cells) Possible mechanism is the release of heat or H 2 gas during oxidation once the nanoparticles are inside the cells. Flake shaped nanomaterials more toxic than spherical. Comparable toxicity to that of quartz
Aluminum Nanoparticle Characteristics 50 nm aluminum particles from Nanotechnologies, Inc. (NT50 Austin, TX). Supplied as dried gray powder Average Grain Size (TEM): 44 ± 18 nm DLS: Hydrodynamic Radius = 340 ± 210 nm Zeta Potential: +44 mv Solution prepared using probe sonication and degassed 18.2 MΩ water. 100 ppm solution
DLS vs TEM: Aluminum Nanoparticles TEM of aluminum nanoparticles: Grain Size: 44 ± 18 nm DLS of aqueous suspension of aluminum nanoparticles: 340 ± 210 nm
Transport of Aluminum in Sand 1.0 0.9 0.8 0.7 0.6 C/C0 0.5 0.4 0.3 0.2 0.1 0.0 0 5 10 15 20 25 30 Pore Volumes Nanoparticle flow through a 7 cm sand (60 mesh) column at a rate of 0.05 ml / minute.
Transport of Aluminum in Soil 1.0 0.9 0.8 0.7 0.6 C/C0 0.5 0.4 0.3 0.2 0.1 0.0 0 5 10 15 20 25 30 35 40 45 50 Pore Volumes Nanoparticle flow through a 7 cm soil column at a rate of 0.05 ml / minute.
Transport of Gold Nanoparticles in Sand Aluminum nanoparticles bind strongly to sand until sand is saturated Even higher retention rates are demonstrated when looking at transport in soil Rate dependent transport effects are observed Transport is complicated by oxidation of aluminum nanoparticles in water
Conclusions and Future Directions Further studies will use precisely fabricated nanoparticles where a single variable is changed for each run (size, shape, surface chemistry, etc.) Transport dependence on flow rates, ph, TOC, conductivity, and particle loading levels will be investigated Develop models to link nanoparticle characteristics to transport dynamics.
Acknowledgements Eglin AFB: Tonya Savage Mitch Bogle AF SBIR Phase II Contract: FA8651-06-C0136