More than the ions: The effects of silver nanoparticles on

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1 Supporting Information More than the ions: The effects of silver nanoparticles on Lolium multiflorum Liyan Yin 1,2, 3 Yingwen Cheng 2,4 Benjamin Espinasse 2,5 Benjamin P. Colman 2,3 Melanie Auffan 6 Mark Wiesner 2,5 Jie Liu 2,4 Emily S. Bernhardt 2,3 1 Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, , People s Republic of China 2 Center for the Environmental Implications of Nanotechnology 3 Department of Biology, Duke University, Durham, NC Department of Chemistry, Duke University, Durham, NC Department of Civil and Environmental Engineering Department 6 CEREGE UMR 6635 CNRS/Aix-Marseille university, iceint international Consortium for the Environmental Implications of NanoTechnology, Aix-en-Provence, France Corresponding Author Emily S. Bernhardt Box Department of Biology Duke University Durham, NC ebernhar@duke.edu Phone: Number of tables: 2 Number of figures: 8 S1

2 SUPPORTING INFORMATION SUPPLEMENTAL METHODS - PREPARATION OF AGNP SOLUTIONS The 6 nm GA-coated AgNPs were synthesized by quickly adding 15 ml of 0.08 M NaBH 4 (Aldrich, Milwaukee, USA) to a 270 ml aqueous solution containing 0.3 g L -1 GA (Fisher, Fair Lawn, USA) and 2 mm AgNO 3 (Fisher, Fair Lawn, USA) while under vigorous stirring for 10 min to allow sufficient reaction. Nanoparticles were separated from the synthesis solution by using an Optima L-100XP ultracentrifuge (Beckman Coulter, Brea, USA) at 41,000 rpm (F=195,000g). The precipitate was redispersed in 100 ml nanopure water (resistivity > 18 MΩ cm, ph 5.8) by 10 min of sonication at 100W with a Sonicator 4000 (Misonix, QSonica, Newton, USA) equipped with a ½ inch diameter flat titanium tip. Temperature was controlled by using an ice-water bath. The ultracentrifugation and redispersion steps were repeated three times before use in the seed germination experiments to ensure nanoparticle purity. The 25 nm GA-coated AgNPs were prepared by adding 1 ml of aqueous 1 M trisodium citrate (Fisher, Fair Lawn, USA) into a boiling solution containing 10 ml GA (10 g L -1 ), 5 ml AgNO 3 (0.1M), and 34 ml nanopure water while vigorously stiring. After 10 min of reaction, the suspension was cooled in an ice-bath. These nanoparticles were purified by centrifugation (15,000 rpm, 27,000g; Sorvall RC-5B, DuPont Instruments, Wilmington, USA) at). The precipitate was redispersed and centrifuged three times. S2

3 SUPPLEMENTAL RESULTS DETAILED CHARACTERIZATION OF AgNPs The 6 nm and 25 nm GA coating AgNPs are spherical with mean size of 6.0±1.7 nm and 25±4 nm as determined by TEM (Figure S1 A&B). From DLS analysis, particles appeared to be monodisperse (data not shown). The shape and the monodispersity are confirmed by the narrow UV-vis absorption peak around 400 nm (Figure S2). The specific surface area (SSA) was estimated about 100±25 m 2 /g (6 nm diameter), and 24±4 m 2 /g (25 nm diameter). The crystallinity of the nanoparticles in their stock suspensions was analyzed by powder XRD. The position of the main diffraction patterns is in agreement with the crystallographic d-spacing of metallic silver (Ag 0 ) reference standard (Figure S3A). The elemental analysis of the 6 nm GA coating AgNPs particle surfaces by XPS shows signals from metallic silver, carbon and oxygen from the GA coating. While NaBH 4 was used in synthesizing these particles, no boron was detected (Figure S3B). In suspension, the 6 nm and 25 nm nanoparticles have a negative zeta-potential (-49.5±1.5 mv, and -44.6±0.2mV respectively) (Table S2). The concentration of dissolved silver within the stock suspension is less than 3 % weighted: 7.0±0.3 and 0.3±0.01 mg Ag L -1 in 250 mg L -1 6 nm and 25nm GA-coated Ag-NP, respectively. The 6nm AgNPs were very stable during the course of the experiment; at the end of the experiment, there was no measurable change in particle size as determined by TEM (Figure S1 C and D). S3

4 TABLE S1. Effect of engineered nanoparticles (ENPs) on higher plants: MWCNT stands for multiwalled carbon nanotubes Focal Plant species Manifestation of effects Ref ENP(s) Brassica napus, No effects or inhibition of Raphanus sativus, MWCNT; root growth, varied Lin and Xing, Lactuca sativa, Al 2 O 3 ; ZnO; greatly among 2007 Zea mays and Al; Zn nanoparticles and plants Cucumis sativus Growth inhibition, root tip Lin and Xing, Lolium perenne ZnO morphology change 2008 Spinacia oleracea TiO 2 Zea mays magnetic Increases in germination rate, growth, rubisco carboxylase activity, Hill reaction, and chloroplast activity Increased growth at intermediate concentrations Zhang et al., 2005; Gao et al., 2006; Hong et al., 2005a, b; Zheng et al., 2005 Racuciu and Creanga, 2007 Phaseolus vulgaris; Lolium Al No effects Doshi et al., 2008 perenne Cucurbita maxima magnetite Bioaccumulation Zhu et al., 2008 Phaseolus radiatus; Triticum aestivum Lactuca Tomato (cv. Micro-Tom) Cu Pd; Cu; Si; Au MWCNT Bioaccumulation, growth inhibition Increase of root/shoot ratio Increase of germination rate and growth Allium cepa Ag Genotoxicity Lee et al., 2008 Shah and Belozerova, 2009 Khodakovskays et al., 2009 Kumari et al TABLE S2. Physico-chemical characterization of the AgNPs before any incubations. Coating Average Size (nm) zeta-potential (mv) shape GA 6.0± ±1.5 spherical GA 25.0± ±0.2 spherical S4

5 C D FIGURE S1: TEM images of 6nm GA-AgNPs before (A) and after (B) 7 days of seed incubation and 25 nm GA-AgNPs before (C) and after (D) 7 days of seed incubation.. S5

6 A B FIGURE S2. UV-Vis absorption spectrum (A) and particle size distribution (B) of the Gum arabic (GA) coated 6nm AgNPs. The particle size was determined from the TEM image and the size distribution was based on 450 nanoparticles from multiple TEM images. S6

7 35 x 10 3 Survey 5nm GA coate d Silver Nanoparticles O 1s B Ag 3d- Ag 3d CPS 20 Ag 3p- Ag 3p 15 O KLL Ag 3s C 1s 10 Ag MNN c Ag MNN a b 5 Ag 4s Ag 4p- O 2s Binding Energy (ev) FIGURE S3. Powder X-ray diffraction (XRD) shows that the position of the main diffraction patterns is in agreement with the crystallographic d-spacing of metallic silver (Ag 0 ) reference standard (A). XPS shows that Boron is not present on the particle surface (B). Typical B signal is around 185eV. S7

8 A B FIGURE S4. TEM image (A), UV-Vis absorption spectrum (B) and particle size distribution of the Gum arabic (GA) coated 25nm AgNPs. The particle size was determined from the TEM image and the size distribution was based on 350 nanoparticles from multiple TEM images. S8

9 Shoot Root Length, cm DDI Water KNO 3 Cysteine GA FIGURE S5. Effect of KNO 3, cysteine and GA on the seedling growth of L. multiflorum after 5 days exposure. No significant differences were found between the treatments (P<0.05). S9

10 20 Shoot Root Dry weight, mg DDI Water KNO 3 Cysteine GA FIGURE S6. Effect of KNO 3, cysteine and GA on the dry weight of L. multiflorum after 5 days exposure. No significant differences were found between the treatments (P<0.05). S10

11 FIGURE S7. Effect of AgNPs and ionic silver on the root growth of L. multiflorum after 3 days exposure. A: Surpernant of 40 mg L-1 GA-coated nanosilver as control; B: 40 mg L-1 6 nm GA-coated AgNPs; C:40 mg L-1 AgNO 3. It shows control plants have long and strait roots, ionic silver treated plants have long and curved roots, AgNPs treated plants have very short and curved roots. S11

12 FIGURE S8. Light microscopy reveals AgNPs absorbed on root surface. S12

13 FIGURE S9. TEM reveals dark particles within AgNP treated roots. A: control; B 6 nm GA coated AgNPs S13

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