Silver Nanoparticles Accumulate in Food Chain Nate Vetter Chem 4101- Professor Edgar Arriaga December 7, 2011Problem Statement and Hypothesis Problem Statement Silver nanoparticles are being used in wound dressings, catheters, and various household products. Little research has been conducted to evaluate the impact of nanoparticles on terrestrial ecosystems Hypothesis My hypothesis is silver nanoparticles can end up in the drainage, sewage, and waste water we expel which can make its way to the terrestrial ecosystems. Insects can uptake these nanoparticles and the nanoparticles can translate up the food chain as predators eat the prey.Overview Main Analyte: Ag0 Nanoparticles 5-20 nm Possible Concentration in soil: 2.0 to 7.0 μg kg−1 Matrixes: Waste Water, Soil, Plant Material, Worm Tissues Figure 1. Retrieved from Judy J. D. ; Unrine J. M. ; Bertsch P. M. Environ. Sci. Technol. 2011, 45, 776-78Requirements for Successful Analysis 1)Must be able to detect small amounts of analyte a. Low Limit of Detection 2)Must be able to detect small changes in analyte Concentration a. High Sensitivity 3)Results must be reproducible and timely a. High Precision b. High Accuracy c. Fast (minutes, not hours)Studies Needed to Test Hypothesis Identify waste streams with nanoparticles present. Determine greatest area of concentration of silver nanoparticles. Measure concentration of silver nanoparticles in soils near waste streams of interest. Based on concentrations of silver nanoparticles found in soil, construct a study similar using concentrations below, at, and above to determine the effect on accumulation in worms. Figure 2. Retrieved from http://toxics.usgs.gov/highlights/tracing_wastewater.html(accessed Dec 7, 2011)Possible Separation Techniques Technique Pros Cons Ion-exchange Chromatography -Fast (minutes) -Low detection limit (ppm) -Other Ions can be detected -Only separation method is retention time -analyte must be charged Size Exclusion Chromatography (SEC) -Separation based on particle size -Fast -No physical or chemical interaction with analyte -Upper and lower limit to retention time -Possible irreversible adsorption of the particles by column packing material Capillary Electrophoresis (CE) -Very Fast analysis -Low detection limit -Expensive equipmentPossible Detection Techniques Technique Pros Cons Ultraviolet- Visible Absorption (UV-Vis) -Simple -Easy to use -Cheap -High Limit of Detection -Can have high signal noise -Requires Standards Atomic absorption Spectroscopy (AAS) -Low Limit of Detection -Can use solid sample -Requires Standards - Slow -Specialized Equipment Inductively Coupled Plasma – Mass Spectroscopy (ICP-MS) -Low Limit of Detection -Can use solid sample -Highly Sensitive -Requires Standards -Specialized EquipmentBest Separation Technique: Ion-exchange Chromatography Simplified Exchange Equilibrium: It is a non-denaturing technique Speed: Fast (minutes) High Selectivity Example data output Figure 4. Retrieve from Skoog, D.A.; Holler, F. J.; Crouch, S. R. Principles of Instrumental Analysis, 6th ed.; Cengage Learning: California, 2007. Figure 3. Retrieved from Skoog, D.A.; Holler, F. J.; Crouch, S. R. Principles of Instrumental Analysis, 6th ed.; Cengage Learning: California, 2007.Best Detector: AAS Multi-element analysis Possible limit of detection: 0.1 – 100 pg AA-500 series specifications High Sensitivity - > 0,85 Abs with 5ppm Cu Resolution – Better than 0.25 nm at 200 nm Figure 5. Retrieved From Skoog, D.A.; Holler, F. J.; Crouch, S. R. Principles of Instrumental Analysis, 6th ed.; Cengage Learning: California, 2007. Figure 6. Retrieve from EPOND. AAS Instrumentation. http://www.e-pond.biz/aas_instr.html(accessed Dec 7, 2011)Experimental Sample Preparation Digestion/microcentrifuge - Using hydrochloric acid and hydrogen peroxide, digest the tissues of the worms or food source. Centrifuge the sample to extract the silver from the matrix. Vacuum Filter – Pores on filter should remove debris in sample but not impede nanoparticles. Dry/Store – Rotovap to remove solvents and store at room temperature until needed Figure 7. Retrieved from http://www.dynamicstar.com.hk/page12.html(Accessed Dec 7, 2011) Figure 8. Retrieved from http://www.komline.com/docs/rotary_drum_vacuum_filter.html(Accessed Dec 7, 2011) Figure 9. Retrieved from http://www.willequipped.com/rotovap.html(accessed Dec. 7, 2011)Possible Outcomes Predicted Results: Worms cannot shed the silver nanoparticles efficiently, resulting in concentration in tissues far exceeding that of their food source. The results of this study should demonstrate trophic transfer and biomagnification of silver nanoparticles from a primary producer to a primary consumer. The observation that nanoparticles could biomagnify highlights the importance of considering dietary uptake as a pathway for nanoparticle exposure. This raises questions about potential human exposure to nanoparticles from long-term land application of biosolids. Figure 10. Retrieved from http://cen.acs.org/articles/88/web/2010/10/Nanoparticles-Worm-Way-Food-Web.html(accessed Dec 7, 2011)References 1. AshaRani, P. V.; Kah Mun G. L.; Hande M. P.; Valiyaveettil, S. Cytotoxicity and Genotoxicity of Silver Nanoparticles in Human Cells. ACS Nano, 2009, 3 (2), 279-290 2. Jensen, T.; Schatz, G.C.; Van Duyne, R. P. Nanosphere Lithography: Surface Plasmon Resonance Spectrum of a Periodic Array of Silver Nanoparticles by Ultraviolet−Visible Extinction Spectroscopy and Electrodynamic Modeling. J. Phys. Chem. B.1999, 103, 2394-2401 3. Judy J. D. ; Unrine J. M. ; Bertsch P. M. Evidence for Biomagnification of Gold Nanoparticles within a Terrestrial Food Chain. Environ. Sci. Technol. 2011, 45, 776-78 4. Lim, S. F.; Riehn R.; Ryu W. S. ; Khanarian N. ; Tung C. ; Tank D. ; Austin R. H. In Vivo and Scanning Electron Microscopy Imaging of Upconverting Nanophosphors in Caenorhabditis elegans. Am. Chem. Soc. 2006, 6, 169-174 5. Link, S.; Wang, Z.L.; El-Sayed, M.A. Alloy Formation of Gold-Silver Nanoparticles and the Dependence of the Plasmon Absorption on Their Composition. J. Phys. Chem. B.1999, 103, 3529-3533 6. Journal of Nanobiotechnology. Silver nanoparticles.
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