Professional Education


  • Doctor of Philosophy, Carnegie Mellon University (2019)
  • Master of Science, Carnegie Mellon University (2016)
  • BS, Oberlin College, Chemistry (2014)

Stanford Advisors


All Publications


  • Protein coating composition targets nanoparticles to leaf stomata and trichomes. Nanoscale Spielman-Sun, E., Avellan, A., Bland, G. D., Clement, E. T., Tappero, R. V., Acerbo, A. S., Lowry, G. V. 2020

    Abstract

    Plant nanobiotechnology has the potential to revolutionize agriculture. However, the lack of effective methods to deliver nanoparticles (NPs) to the precise locations in plants where they are needed impedes these technological innovations. Here, model gold nanoparticles (AuNP) were coated with citrate, bovine serum albumin (BSA) as a protein control, or LM6-M, an antibody with an affinity for functional groups unique to stomata on leaf surfaces to deliver the AuNPs to stomata. One-month-old Vicia faba leaves were exposed via drop deposition to aqueous suspensions of LM6-M-coated AuNPs and allowed to air dry. After rinsing, Au distribution on the leaf surface was investigated by enhanced dark-field microscopy and X-ray fluorescence mapping. While citrate-coated AuNPs randomly covered the plant leaves, LM6M-AuNPs strongly adhered to the stomata and remained on the leaf surface after rinsing, and BSA-AuNPs specifically targeted trichome hairs. To the authors' knowledge, this is the first report of active targeting of live leaf structures using NPs coated with molecular recognition molecules. This proof-of-concept study provides a strategy for future targeted nanopesticide delivery research.

    View details for DOI 10.1039/c9nr08100c

    View details for PubMedID 31998910

  • Differential Reactivity of Copper- and Gold-Based Nanomaterials Controls Their Seasonal Biogeochemical Cycling and Fate in a Freshwater Wetland Mesocosm. Environmental science & technology Avellan, A., Simonin, M., Anderson, S. M., Geitner, N. K., Bossa, N., Spielman-Sun, E., Bernhardt, E. S., Castellon, B. T., Colman, B. P., Cooper, J. L., Ho, M., Hochella, M. F., Hsu-Kim, H., Inoue, S., King, R. S., Laughton, S., Matson, C. W., Perrotta, B. G., Richardson, C. J., Unrine, J. M., Wiesner, M. R., Lowry, G. V. 2020

    Abstract

    Reliable predictions of the environmental fate and risk of engineered nanomaterials (ENMs) require a better understanding of ENM reactivity in complex, biologically active systems for chronic low-concentration exposure scenarios. Here, simulated freshwater wetland mesocosms were dosed with ENMs to assess how their reactivity and seasonal changes in environmental parameters influence ENM fate in aquatic systems. Copper-based ENMs (Kocide), known to dissolve in water, and gold nanoparticles (AuNPs), stable against dissolution in the absence of specific ligands, were added weekly to mesocosm waters for 9 months. Metal accumulation and speciation changes in the different environmental compartments were assessed over time. Copper from Kocide rapidly dissolved likely associating with organic matter in the water column, transported to terrestrial soils and deeper sediment where it became associated with organic or sulfide phases. In contrast, Au accumulated on/in the macrophytes where it oxidized and transferred over time to surficial sediment. A dynamic seasonal accumulation and metal redox cycling were found between the macrophyte and the surficial sediment for AuNPs. These results demonstrate the need for experimental quantification of how the biological and chemical complexity of the environment, combined with their seasonal variations, drive the fate of metastable ENMs.

    View details for DOI 10.1021/acs.est.9b05097

    View details for PubMedID 31951397

  • Nanoparticle surface charge influences translocation and leaf distribution in vascular plants with contrasting anatomy ENVIRONMENTAL SCIENCE-NANO Spielman-Sun, E., Avellan, A., Bland, G. D., Tappero, R., Acerbo, A. S., Unrine, J. M., Giraldo, J., Lowry, G. 2019; 6 (8): 2508–19

    View details for DOI 10.1039/c9en00626e

    View details for Web of Science ID 000479313800010

  • Effect of Soil Organic Matter, Soil pH, and Moisture Content on Solubility and Dissolution Rate of CuO NPs in Soil ENVIRONMENTAL SCIENCE & TECHNOLOGY Gao, X., Rodrigues, S. M., Spielman-Sun, E., Lopes, S., Rodrigues, S., Zhang, Y., Avellan, A., Duarte, R. O., Duarte, A., Casman, E. A., Lowry, G. V. 2019; 53 (9): 4959–67

    Abstract

    The objectives of this research were to quantify the impact of organic matter content, soil pH and moisture content on the dissolution rate and solubility of copper oxide nanoparticles (CuO NPs) in soil, and to develop an empirical model to predict the dissolution kinetics of CuO NPs in soil. CuO NPs were dosed into standard LUFA soils with various moisture content, pH and organic carbon content. Chemical extractions were applied to measure the CuO NP dissolution kinetics. Doubling the reactive organic carbon content in LUFA 2.1 soil increased the solubility of CuO NP 2.7-fold but did not change the dissolution rate constant. Increasing the soil pH from 5.9 to 6.8 in LUFA 2.2 soil decreased the dissolution rate constant from 0.56 mol1/3·kg1/3·s-1 to 0.17 mol1/3·kg1/3·s-1 without changing the solubility of CuO NP in soil. For six soils, the solubility of CuO NP correlated well with soil organic matter content ( R2 = 0.89) independent of soil pH. In contrast, the dissolution rate constant correlated with pH for pH < 6.3 ( R2 = 0.89), independent of soil organic matter content. These relationships predicted the solubility and dissolution rate constants of CuO NP in two test soils (pH 5.0 and pH 7.6). Moisture content showed negligible impact on the dissolution kinetics of CuO NPs. Our study suggests that soil pH and organic matter content affect the dissolution behavior of CuO NP in soil in a predictable manner.

    View details for DOI 10.1021/acs.est.8b07243

    View details for Web of Science ID 000467641800032

    View details for PubMedID 30920811

  • Nanoparticle Size and Coating Chemistry Control Foliar Uptake Pathways, Translocation, and Leaf-to-Rhizosphere Transport in Wheat ACS NANO Avellan, A., Yun, J., Zhang, Y., Spielman-Sun, E., Unrine, J. M., Thieme, J., Li, J., Lombi, E., Bland, G., Lowry, G. V. 2019; 13 (5): 5291–5305

    Abstract

    Nanoenabled foliar-applied agrochemicals can potentially be safer and more efficient than conventional products. However, limited understanding about how nanoparticle properties influence their interactions with plant leaves, uptake, translocation through the mesophyll to the vasculature, and transport to the rest of the plant prevents rational design. This study used a combination of Au quantification and spatial analysis to investigate how size (3, 10, or 50 nm) and coating chemistry (PVP versus citrate) of gold nanoparticles (AuNPs) influence these processes. Following wheat foliar exposure to AuNPs suspensions (∼280 ng per plant), adhesion on the leaf surface was increased for smaller sizes, and PVP-AuNPs compared to citrate-AuNPs. After 2 weeks, there was incomplete uptake of citrate-AuNPs with some AuNPs remaining on the outside of the cuticle layer. However, the fraction of citrate-AuNPs that had entered the leaf was translocated efficiently to the plant vasculature. In contrast, for similar sizes, virtually all of the PVP-AuNPs crossed the cuticle layer after 2 weeks, but its transport through the mesophyll cells was lower. As a consequence of PVP-AuNP accumulation in the leaf mesophyll, wheat photosynthesis was impaired. Regardless of their coating and sizes, the majority of the transported AuNPs accumulated in younger shoots (10-30%) and in roots (10-25%), and 5-15% of the NPs <50 nm were exuded into the rhizosphere soil. A greater fraction of larger sizes AuNPs (presenting lower ζ potentials) was transported to the roots. The key hypotheses about the NPs physical-chemical and plant physiology parameters that may matter to predict leaf-to-rhizosphere transport are also discussed.

    View details for DOI 10.1021/acsnano.8b09781

    View details for Web of Science ID 000469886300038

    View details for PubMedID 31074967

  • Gold nanoparticle biodissolution by a freshwater macrophyte and its associated microbiome NATURE NANOTECHNOLOGY Avellan, A., Simonin, M., McGivney, E., Bossa, N., Spielman-Sun, E., Rocca, J. D., Bernhardt, E. S., Geitner, N. K., Unrine, J. M., Wiesner, M. R., Lowry, G. 2018; 13 (11): 1072-+

    Abstract

    Predicting nanoparticle fate in aquatic environments requires mimicking of ecosystem complexity to observe the geochemical processes affecting their behaviour. Here, 12 nm Au nanoparticles were added weekly to large-scale freshwater wetland mesocosms. After six months, ~70% of Au was associated with the macrophyte Egeria densa, where, despite the thermodynamic stability of Au0 in water, the pristine Au0 nanoparticles were fully oxidized and complexed to cyanide, hydroxyls or thiol ligands. Extracted biofilms growing on E. densa leaves were shown to dissolve Au nanoparticles within days. The Au biodissolution rate was highest for the biofilm with the lowest prevalence of metal-resistant taxa but the highest ability to release cyanide, known to promote Au0 oxidation and complexation. Macrophytes and the associated microbiome thus form a biologically active system that can be a major sink for nanoparticle accumulation and transformations. Nanoparticle biotransformation in these compartments should not be ignored, even for nanoparticles commonly considered to be stable in the environment.

    View details for DOI 10.1038/s41565-018-0231-y

    View details for Web of Science ID 000449291700022

    View details for PubMedID 30104621

  • Temporal Evolution of Copper Distribution and Speciation in Roots of Triticum aestivum Exposed to CuO, Cu(OH)(2), and CuS Nanoparticles ENVIRONMENTAL SCIENCE & TECHNOLOGY Spielman-Sun, E., Lombi, E., Donner, E., Avellan, A., Etschmann, B., Howard, D., Lowry, G. V. 2018; 52 (17): 9777–84

    Abstract

    Utilization of nanoparticles (NP) in agriculture as fertilizers or pesticides requires an understanding of the NP properties influencing their interactions with plant roots. To evaluate the influence of the solubility of Cu-based NP on Cu uptake and NP association with plant roots, wheat seedlings were hydroponically exposed to 1 mg/L of Cu NPs with different solubilities [CuO, CuS, and Cu(OH)2] for 1 h then transferred to a Cu-free medium for 48 h. Fresh, hydrated roots were analyzed using micro X-ray fluorescence (μ-XRF) and imaging fluorescence X-ray absorption near edge spectroscopy (XANES imaging) to provide laterally resolved distribution and speciation of Cu in roots. Higher solubility Cu(OH)2 NPs provided more uptake of Cu after 1 h of exposure, but the lower solubility materials (CuO and CuS) were more persistent on the roots and continued to deliver Cu to plant leaves over the 48 h depuration period. These results demonstrate that NPs, by associating to the roots, have the potential to play a role in slowly providing micronutrients to plants. Thus, tuning the solubility of NPs may provide a long-term slow delivery of micronutrients to plants and provide important information for understanding mechanisms responsible for plant uptake, transformation, and translocation of NPs.

    View details for DOI 10.1021/acs.est.8b02111

    View details for Web of Science ID 000444061100025

    View details for PubMedID 30078329

  • Effect of silver concentration and chemical transformations on release and antibacterial efficacy in silver-containing textiles NANOIMPACT Spielman-Sun, E., Zaikova, T., Dankovich, T., Yun, J., Ryan, M., Hutchison, J. E., Lowry, G. V. 2018; 11: 51–57
  • Elucidating nanoparticle-plant leaf interactions, uptake, and mobility for designing highly efficient foliar-applied agrochemicals Avellan, A., Yun, J., Spielman-Sun, E., Lowry, G. AMER CHEMICAL SOC. 2018
  • Toward improving agrochemical efficiency: Impact of Cu-based nanoparticle solubility on metal uptake, speciation, translocation, and distribution in Triticum aestivum (wheat) Spielman-Sun, E., Lombi, E., Donner, E., Etschmann, B., Howard, D., Lowry, G. AMER CHEMICAL SOC. 2018
  • Impact of Surface Charge on Cerium Oxide Nanoparticle Uptake and Translocation by Wheat (Triticum aestivum) ENVIRONMENTAL SCIENCE & TECHNOLOGY Spielman-Sun, E., Lombi, E., Donner, E., Howard, D., Unrine, J. M., Lowry, G. V. 2017; 51 (13): 7361–68

    Abstract

    Nanoparticle (NP) physiochemical properties, including surface charge, affect cellular uptake, translocation, and tissue localization. To evaluate the influence of surface charge on NP uptake by plants, wheat seedlings were hydroponically exposed to 20 mg/L of ∼4 nm CeO2 NPs functionalized with positively charged, negatively charged, and neutral dextran coatings. Fresh, hydrated roots and leaves were analyzed at various time points over 34 h using fluorescence X-ray absorption near-edge spectroscopy to provide laterally resolved spatial distribution and speciation of Ce. A 15-20% reduction from Ce(IV) to Ce(III) was observed in both roots and leaves, independent of NP surface charge. Because of its higher affinity with negatively charged cell walls, CeO2(+) NPs adhered to the plant roots the strongest. After 34 h, CeO2(-), and CeO2(0) NP exposed plants had higher Ce leaf concentrations than the plants exposed to CeO2(+) NPs. Whereas Ce was found mostly in the leaf veins of the CeO2(-) NP exposed plant, Ce was found in clusters in the nonvascular leaf tissue of the CeO2(0) NP exposed plant. These results provide important information for understanding mechanisms responsible for plant uptake, transformation, and translocation of NPs, and suggest that NP coatings can be designed to target NPs to specific parts of plants.

    View details for DOI 10.1021/acs.est.7b00813

    View details for Web of Science ID 000405056200007

    View details for PubMedID 28575574

  • Tuning NP properties for optimizing plant uptake and translocation Lowry, G., Spielman-Sun, E., Lombi, E., Unrine, J. AMER CHEMICAL SOC. 2017
  • Time and Nanoparticle Concentration Affect the Extractability of Cu from CuO NP-Amended Soil ENVIRONMENTAL SCIENCE & TECHNOLOGY Gao, X., Spielman-Sun, E., Rodrigues, S. M., Casman, E. A., Lowry, G. V. 2017; 51 (4): 2226–34

    Abstract

    We assess the effect of CuO nanoparticle (NP) concentration and soil aging time on the extractability of Cu from a standard sandy soil (Lufa 2.1). The soil was dosed with CuO NPs or Cu(NO3)2 at 10 mg/kg or 100 mg/kg of total added Cu, and then extracted using either 0.01 M CaCl2 or 0.005 M diethylenetriaminepentaacetic acid (DTPA) (pH 7.6) extraction fluid at selected times over 31 days. For the high dose of CuO NPs, the amount of DTPA-extractable Cu in soil increased from 3 wt % immediately after mixing to 38 wt % after 31 days. In contrast, the extractability of Cu(NO3)2 was highest initially, decreasing with time. The increase in extractability was attributed to dissolution of CuO NPs in the soil. This was confirmed with synchrotron X-ray absorption near edge structure measurements. The CuO NP dissolution kinetics were modeled by a first-order dissolution model. Our findings indicate that dissolution, concentration, and aging time are important factors that influence Cu extractability in CuO NP-amended soil and suggest that a time-dependent series of extractions could be developed as a functional assay to determine the dissolution rate constant.

    View details for DOI 10.1021/acs.est.6b04705

    View details for Web of Science ID 000394724300037

    View details for PubMedID 28106997

  • In Situ Measurement of CuO and Cu(OH)(2) Nanoparticle Dissolution Rates in Quiescent Freshwater Mesocosms ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS Vencalek, B. E., Laughton, S. N., Spielman-Sun, E., Rodrigues, S. M., Unrine, J. M., Lowry, G. V., Gregory, K. B. 2016; 3 (10): 375–80
  • Impact of metal and metal oxide nanoparticle speciation and solubility on their bioavailability to terrestrial and aquatic plants Lowry, G., Stegemeier, J., Gao, X., Spielman-Sun, E., Rodrigues, S. AMER CHEMICAL SOC. 2016
  • Thermal decomposition of nano-enabled thermoplastics: Possible environmental health and safety implications JOURNAL OF HAZARDOUS MATERIALS Sotiriou, G. A., Singh, D., Zhang, F., Chalbot, M. G., Spielman-Sun, E., Hoering, L., Kavouras, I. G., Lowry, G. V., Wohlleben, W., Demokritou, P. 2016; 305: 87–95

    Abstract

    Nano-enabled products (NEPs) are currently part of our life prompting for detailed investigation of potential nano-release across their life-cycle. Particularly interesting is their end-of-life thermal decomposition scenario. Here, we examine the thermal decomposition of widely used NEPs, namely thermoplastic nanocomposites, and assess the properties of the byproducts (released aerosol and residual ash) and possible environmental health and safety implications. We focus on establishing a fundamental understanding on the effect of thermal decomposition parameters, such as polymer matrix, nanofiller properties, decomposition temperature, on the properties of byproducts using a recently-developed lab-based experimental integrated platform. Our results indicate that thermoplastic polymer matrix strongly influences size and morphology of released aerosol, while there was minimal but detectable nano-release, especially when inorganic nanofillers were used. The chemical composition of the released aerosol was found not to be strongly influenced by the presence of nanofiller at least for the low, industry-relevant loadings assessed here. Furthermore, the morphology and composition of residual ash was found to be strongly influenced by the presence of nanofiller. The findings presented here on thermal decomposition/incineration of NEPs raise important questions and concerns regarding the potential fate and transport of released engineered nanomaterials in environmental media and potential environmental health and safety implications.

    View details for DOI 10.1016/j.jhazmat.2015.11.001

    View details for Web of Science ID 000369451400010

    View details for PubMedID 26642449

    View details for PubMedCentralID PMC4707061

  • Toward a mechanistic understanding of the effect of natural organic matter coatings on nanoparticle aggregation Lowry, G., Louie, S., Spielman-Sun, E., Tilton, R. AMER CHEMICAL SOC. 2015
  • Correlation of the Physicochemical Properties of Natural Organic Matter Samples from Different Sources to Their Effects on Gold Nanoparticle Aggregation in Monovalent Electrolyte ENVIRONMENTAL SCIENCE & TECHNOLOGY Louie, S. M., Spielman-Sun, E. R., Small, M. J., Tilton, R. D., Lowry, G. V. 2015; 49 (4): 2188–98

    Abstract

    Engineered nanoparticles (NPs) released into natural environments will interact with natural organic matter (NOM) or humic substances, which will change their fate and transport behavior. Quantitative predictions of the effects of NOM are difficult because of its heterogeneity and variability. Here, the effects of six types of NOM and molecular weight fractions of each on the aggregation of citrate-stabilized gold NPs are investigated. Correlations of NP aggregation rates with electrophoretic mobility and the molecular weight distribution and chemical attributes of NOM (including UV absorptivity or aromaticity, functional group content, and fluorescence) are assessed. In general, the >100 kg/mol components provide better stability than lower molecular weight components for each type of NOM, and they contribute to the stabilizing effect of the unfractionated NOM even in small proportions. In many cases, unfractionated NOM provided better stability than its separated components, indicating a synergistic effect between the high and low molecular weight fractions for NP stabilization. Weight-averaged molecular weight was the best single explanatory variable for NP aggregation rates across all NOM types and molecular weight fractions. NP aggregation showed poorer correlation with UV absorptivity, but the exponential slope of the UV-vis absorbance spectrum was a better surrogate for molecular weight. Functional group data (including reduced sulfur and total nitrogen content) were explored as possible secondary parameters to explain the strong stabilizing effect of a low molecular weight Pony Lake fulvic acid sample to the gold NPs. These results can inform future correlations and measurement requirements to predict NP attachment in the presence of NOM.

    View details for DOI 10.1021/es505003d

    View details for Web of Science ID 000349806400027

    View details for PubMedID 25611369

  • Properties of various natural organic matter samples that control gold nanoparticle aggregation Louie, S. M., Spielman-Sun, E., Tilton, R. D., Lowry, G. V. AMER CHEMICAL SOC. 2014