Abstract:
The study investigated the interactions of coated-gold engineered nanoparticles (nAu)
with the aquatic higher plant Salvinia minima Baker in 2,7, and 14 d. Herein, the nAu concentration
of 1000 g/L was used; as in lower concentrations, analytical limitations persisted but >1000 g/L
were deemed too high and unlikely to be present in the environment. Exposure of S. minima to
1000 g/L of citrate (cit)- and branched polyethyleneimine (BPEI)-coated nAu (5, 20, and 40 nm) in
10% Hoagland’s medium (10 HM) had marginal effect on biomass and growth rate irrespective of nAu
size, coating type, or exposure duration. Further, results demonstrated that nAu were adsorbed on
the plants’ roots irrespective of their size or coating variant; however, no evidence of internalization
was apparent, and this was attributed to high agglomeration of nAu in 10 HM. Hence, adsorption
was concluded as the basic mechanism of nAu accumulation by S. minima. Overall, the long-term
exposure of S. minima to nAu did not inhibit plant biomass and growth rate but agglomerates on
plant roots may block cell wall pores, and, in turn, alter uptake of essential macronutrients in plants,
thus potentially affecting the overall ecological function.
Description:
Supplementary Materials: Equation (S1): Calculation of ζ potentials using Smoluchowski equation,
Equation (S2): Calculation of ionic strength (IS) of the exposure medium, Figure S1: TEM images of
nAu (a) 5 nm-Cit, (b) 20 nm-Cit, (c) 40 nm-Cit, (d) 5 nm-BPEI, (e) 20 nm-BPEI, (f) and 40 nm-BPEI,
Table S1: Composition of Hoagland’s medium, Table S2: Mean sizes (nm) of nAu obtained using TEM,
Figure S2: Particle size distribution of nAu at 1000 µg/L in 10% Hoagland’s medium measured using
Dynamic Light Scattering technique (a) 5 nm Cit-nAu, (b) 20 nm Cit-nAu, (c) 40 nm Cit-nAu, (d) 5 nm
BPEI-nAu, (e) 20 nm BPEI-nAu, and (f) 40 nm BPEI-nAu, Figure S3: Hydrodynamic diameters of
nAu in de-ionized water and 10% Hoagland’s medium tracked using Dynamic Light Scattering
technique over 48 h; (a) 5 nm Cit-nAu, (b) 20 nm Cit-nAu, (c) 40 nm Cit-nAu, (d) 5 nm BPEI-nAu,
(e) 20 nm BPEI-nAu, and (f) 40 nm BPEI-nAu, Figure S4: Zeta potentials of nAu in de-ionized
water and 10% Hoagland’s medium obtained using Dynamic Light Scattering technique over 48 h;
(a) 5 nm Cit-nAu, (b) 20 nm Cit-nAu, (c) 40 nm Cit-nAu, (d) 5 nm BPEI-nAu, (e) 20 nm BPEI-nAu,
and (f) 40 nm BPEI-nAu, Figure S5: UV-vis spectrum of nAu in de-ionized water as a function
of time; (a) 5 nm Cit-nAu, (b) 20 nm Cit-nAu, (c) 40 nm Cit-nAu, (d) 5 nm BPEI-nAu, (e) 20 nm
BPEI-nAu, and (f) 40 nm BPEI-nAu, Figure S6: in situ nAu concentration (particles/mL) examined
using Nanoparticle Tracking Analysis (NTA), Figure S7: TEM-EDX spectra confirming the absence of
nAu internalization on plant roots: (a) control, (b) 5 nm cit-nAu, (c) 20 nm-cit nAu, (d) 40 nm cit-nAu,
(e) 5 nm BPEI-nAu, (f) 20 nm BPEI-nAu, and (g) 40 nm BPEI.
