Session IIIB

Monday, May 16th

Session IIIB


T23

Mass Spectral Identification of Biomarkers of Exposure to Silver Nanoparticles in Corn Roots

Nita Chavez Soria, Mary A. Bisson, G. Ekin Atilla-Gokcumen, and Diana S. Aga

University at Buffalo, Department of Chemistry

Engineered nanomaterials have led to advances in technology and medicine due to their unique properties and characteristics. Their production and usage is rapidly growing, raising concerns on their impact on environmental and human health. Silver nanoparticles (AgNPs) are used in many facets of industry due to their antimicrobial properties. They can be found in clothing, food packaging, cosmetics and electronics. Due to their wide range of applications, AgNP containing products are expected to be disposed of in landfills. Alternatively, they can leach out from textiles during washing, reach wastewater treatment plants, and accumulate in biosolids. This can later be land-applied in agricultural fields and eventually absorbed by crops. Understanding the effects of AgNPs on the growth and health of crops is paramount. Root systems secrete chemicals into the environment, which dictates their interaction not only with soil, but also with microorganisms present in the rhizosphere. The goal of our project is to determine the impact of AgNPs on hydroponically grown corn. Corn plants were exposed to AgNPs, and changes in the composition of polar metabolites in the roots were determined using liquid chromatography and high-resolution mass spectrometry. Evaluating the impact of metabolic changes will be critical for the biomarker identification in exposure of affected plants to AgNPs. The results will provide fundamental understanding and insight on the interactions of nanomaterials exposed to an agricultural crop, and the environmental impact of the new technology.


T24

Role of Nucleation Mechanism on the Size Dependent Morphology of Organic Aerosol

Muhammad Altaf, Andreas Zuend, and Miriam Freedman

Penn State University, Department of Chemistry

Aerosol particles composed of mixtures of organic and inorganic compounds can undergo liquid-liquid phase separation to form an aqueous two phase system.  In the submicron size regime, the morphology of particles is dependent on size, where for some systems, small particles are homogeneous and large particles are phase separated.  In this work, the origins of the size dependence are explored by probing the morphology of aqueous poly(ethylene glycol) 400 (PEG-400)/ammonium sulfate mixtures for many different particle compositions.  Surprisingly, we observe size dependence at some organic/inorganic ratios, but not at others.  Our results suggest that phase separation occurs by different mechanisms for the different ratios.  At organic/inorganic mass ratios near the critical point where the activation barrier for phase separation is reduced, phase separation is seen at all particle sizes studied.  Away from the critical point, the activation barrier leads to a size dependent morphology.  Our results suggest that the size dependence occurs due to activated processes.  This may have important consequences for the growth of new particles and the activation of cloud condensation nuclei, which impact Earth’s radiation budget.

 

T25

Imaging Silver Nanoparticles (AgNPs) in Plant Tissue by Cryo-Time-of-Flight Secondary Ion Mass Spectrometry (Cryo-ToF-SIMS)

Angelina Montes,1 Mary Bisson,2 and Joseph Gardella Jr.1

(1)   University at Buffalo, Department of Chemistry (2)   University at Buffalo, Department of Biological Sciences

Silver nanoparticles (AgNPs) are incorporated into commercial products because of their beneficial properties.1 As their applications become more diverse, there is an increased risk of entry into the environment such as from groundwater runoff.  Their unique properties raise concerns regarding fate, transport, and their subsequent effects on plants and animals. While the presence of AgNPs in water, soil, and plants has been established, the mechanism by which these or are sequestered in plants is not clear.2 The present work aims to study the uptake of AgNPs in Arabidopsis thaliana. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) imaging has been used to determine spatial distribution and spectral information characteristic of the plant, ionic Ag, AgNPs, and plants exposed to either ionic Ag or AgNPs. An ION-TOF V equipped with a bismuth primary ion source and a cryogenic chamber was used to study Arabidopsis in its native state.  Cryo-ToF-SIMS images and spectra were collected from surfaces of frozen-hydrated Arabidopsis stem cross-sections treated with AgNPs or silver nitrate.  Morphological features similar to those seen by optical microscopy were identified using the burst alignment mode of analysis.  Additional analysis on the same sample area using the high current bunched mode allowed for identification of specific regions where the AgNPs are present. By using the ratio of Ag+/Ag3+, it is possible to distinguish the differences between ionic Ag and AgNPs within Arabidopsis in its native state while preserving spatial resolution.

(1) Rubiales, D. and A. Perez-de-Luque, Pest Manag. Sci. 2009, 65, 540-545.                                                                                 (2) Wang, J. et. al.  Environ. Sci. Technol. 2013, 47, 5442-5449.

 

T26

Investigation of Trace Element Distribution and Dose-Dependence in Caprine Horn using Inductively-Coupled Plasma Mass Spectrometry (ICP-MS) and Synchrotron X-Ray Fluorescence (SXRF)

Mina Tehrani and Dr. Patrick Parsons

SUNY Albany and NYSDOH Wadsworth Center

Keratinized tissue, including skin, hair, nail, and horn, is the main component of the outer covering of vertebrates. Given their ability to incorporate trace elements via environmental exposure, and to preserve trace element content over time, keratin tissues such as hair and nails are widely used in human biomonitoring. However, qualitative and quantitative knowledge of the relationship between exposure and elemental distribution in keratin tissues is incomplete, weakening the reliability of keratin tissue analyses. In this work, elemental spatial distributions in a model keratin tissue, horn derived post mortem from lead-dosed goats, were investigated using two complementary techniques. Preliminary validation using two hair certified reference materials was conducted for both methods. Concentrations of lead and six other trace elements along horn lengths were measured using solution-nebulization ICP-MS. SXRF generated elemental distribution maps for five elements in horn cross sections. ICP-MS results suggest correlation between lead concentration in horn and dose above seven years of age, with a spike in concentration in the horn tip, corresponding to early non-dosed years. This unexpected spike may be explained by a growth pattern in which the horn tip contains keratin layers grown throughout the animal’s life. SXRF maps support this pattern, as well as providing preliminary information about cysteine distribution and the effect of pigmentation on zinc content in horn. Among other findings, this study suggests that lead is incorporated into horn at low levels in a dose-dependent manner. Due to horn’s similarity to human keratins, these findings may offer insight into longstanding biomonitoring challenges. Further investigation into the distribution of lead in horn is needed and will be conducted using laser-ablation ICP-MS.