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Zein nanoparticles uptake by hydroponically grown soybean plants Kurt Ristroph, Carlos E Astete, Ede Bodoki, and Cristina M. Sabliov Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b03923 • Publication Date (Web): 17 Nov 2017 Downloaded from http://pubs.acs.org on November 18, 2017
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Environmental Science & Technology
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Zein nanoparticles uptake by hydroponically
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grown soybean plants
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Kurt D. Ristroph, Carlos E. Astete, Ede Bodoki, and Cristina M. Sabliov*
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141 E. B. Doran Bldg, Department of Biological and Agricultural Engineering
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Louisiana State University and LSU Agricultural Center
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Baton Rouge, LA 70803
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Email:
[email protected] 9
KEYWORDS Polymeric nanoparticles, nanodelivery systems, zein, nanoparticle plant interaction, nanoparticle
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uptake kinetics
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ABSTRACT: In the interest of developing and characterizing a polymeric nanoparticle pesticide
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delivery vehicle to soybeans, zein nanoparticle (ZNP) uptake by the roots and biodistribution to
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the leaves of soybean plants was measured. Zein was tagged with fluorescein isothiocyanate
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(FITC) and made into nanoparticles (135±3 nm diameter. 0.202±0.034 PDI and 81±4 mV zeta-
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potential at pH 6) using an emulsion-diffusion method. After ten days of hydroponic exposure,
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association between particles and roots of plants was found to vary based on bulk nanoparticle
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concentration. While 0.37 mg NP/mg dry weight were detected in roots immersed in 0.88 mg
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NP/ml nanoparticle suspension, 0.58 mg NP/mg dry weight associated with roots immersed in a
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high dose nanoparticle suspension of 1.75 mg NP/ml at 10 days. Nanoparticle root uptake
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followed second order kinetics. A small amount of increased fluorescence was detected in the 1
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hydroponically exposed plant’s leaves, suggesting that either small amounts of particles or other
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fluorescent contaminants of zein were up taken by the roots and bio-distributed within the plant.
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To the authors’ knowledge, this is the first study in which the uptake and time-dependent
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association between polymeric nanoparticles and soybeans are quantified.
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1. INTRODUCTION
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In general, concerns over fate and impact of engineered nanoparticles (ENPs) made of
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biodegradable chemical components such as zein, a corn protein, are significantly lower than
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concerns over the use of inorganic metallic and metal oxide ENPs, which are often perceived as
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potentially toxic.1 It is therefore not surprising that most reports investigating ENP impact on
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plants as measured by germination, root elongation, and growth have focused on inorganic
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nanoparticles. Studies of inorganic NPs environmental fate have provided insights on particle
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accumulation in plants and soil, crucial for further use of these materials in agriculture. What is
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known at this point is that plants can uptake ENPs through roots and leaves, but the uptake
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mechanisms are poorly understood, even for inorganic ENPs.2 It has been proposed that ENPs
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can penetrate the root epidermis and endodermis to access the xylem vessel and further
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translocate to the aerial parts of the plant. The leaves can internalize ENPs through the leaf
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stoma, which allows ENPs to reach the vascular system of the plant, with subsequent transport to
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other tissues through the phloem.3-6
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The data available for inorganic nanoparticles suggests that ENPs size, surface charge, functional
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groups, type of plant, stage of plant growth, and exposure duration can all affect the amount of
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ENPs internalized by plants;7-12 such findings are expected to hold true for organic nanoparticles 2
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as well. The literature is diverse, and comparisons between studies are difficult given the
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multitude of plants, conditions, and types of particles tested. A few trends can be identified for
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inorganic nanoparticles. 1. ENP-plant interaction is very much a function of plant type. For
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example, translocation of gold NPs was higher in rice and ryegrass compared to pumpkin and
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radish.13 The internalization of 38 nm CeO2 NPs by maize was not significant,14 while 37 nm
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Fe3O4 NPs, a similar primary particle size, were transported through pumpkin plants15 2. Size of
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the ENPs plays an important role. Nanoparticles of sizes ranging from very small (
