Silver Nanoparticles Accumulate in Food

ChainNate Vetter

Chem 4101- Professor Edgar Arriaga

December 7, 2011

Problem 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

Limit of Detection: 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, 776-78

Requirements for Successful Analysis

1)Must be able to detect small amounts of analyte1)Low Limit of Detection

2)Must be able to detect small changes in analyte Concentration

1)High Sensitivity

3)Results must be reproducible and timely 1)High Precision

2)High Accuracy

3)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 soils, construct a study similar in the lab using concentrations below, at, and above to determine the effect on accumulation in worms.

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 equipment

Possible 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 Equipment

Best Separation Technique: Ion-exchange Chromatography

Speed: Very fast (minutes)

It is a non-denaturing technique that

can be used at all stages and scales

of purification.

Selectivity:  Can resolve molecules

with small differences in charge.

Simplified Exchange Equilibrium:

Figure 2. Retrieve 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 Limit of Detection:

0.1 – 100 pg

Reproducibility: 5-10% High Sensitivity Easy to use Can buy commercially

Figure 3. Retrieved From Skoog, D.A.; Holler, F. J.; Crouch, S. R. Principles of Instrumental Analysis, 6th ed.; Cengage Learning: California, 2007.

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 matix.

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

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 can 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 containing nanoparticles.

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. http://www.jnanobiotechnology.com/content/3/1/6/figure/F1?highres=y (accessed Oct 26, 2011)

7. Nanocs. Silver nanoparticles. http://www.nanocs.com/Silver_nanoparticles.htm (accessed Oct 26, 2011) 8. Wei, G. T.; Liu, F.K.; Wang C. Shape Separation of Nanometer Gold Particles by Size-Exclusion

Chromatography. Anal. Chem. 1999, 71, 2085-2091 9. Skoog, D.A.; Holler, F. J.; Crouch, S. R. Principles of Instrumental Analysis, 6th ed.; Cengage Learning:

California, 2007.