This presentation is based on our review paper ‘Engineered nanoparticles in the soil and their potential implications to microbial activity’, Geoderma, 2012, 173-174, 19-27 (http://dx.doi.org/10.1016/j.geoderma.2011.12.018)
Engineered nanoparticles in the soil and their Engineered nanoparticles in the soil and their potential implications to microbial activity potential implications to microbial activity R. Dinesh R. Dinesh M. Anandaraj M. Anandaraj V. Srinivasan V. Srinivasan S. Hamza S. Hamza Indian Institute of Spices Research Indian Institute of Spices Research (Indian Council of Agricultural Research) (Indian Council of Agricultural Research) Marikunnu PO., Calicut-673012 Marikunnu PO., Calicut-673012 Kerala State, India Kerala State, India This presentation is based on our review paper ‘Engineered nanoparticles in the soil and their potential implications to microbial activity’, Geoderma, 2012, 173-174, 19-27 (http:// www.sciencedirect.com/science/article/pii/S0016706111003661 )
Transcript
Engineered nanoparticles in the soil and their potential implications to Engineered nanoparticles in the soil and their potential implications to microbial activitymicrobial activity
R. DineshR. Dinesh
M. AnandarajM. Anandaraj
V. SrinivasanV. Srinivasan
S. HamzaS. Hamza
Indian Institute of Spices ResearchIndian Institute of Spices Research
(Indian Council of Agricultural Research)(Indian Council of Agricultural Research)
This presentation is based on our review paper ‘Engineered nanoparticles in the soil and their potential implications to microbial activity’, Geoderma, 2012, 173-174, 19-27 (http://www.sciencedirect.com/science/article/pii/S0016706111003661) (http://dx.doi.org/10.1016/j.geoderma.2011.12.018)
The U.S. National Nanotechnology Initiative (NNI) has defined The U.S. National Nanotechnology Initiative (NNI) has defined
nanotechnology as the nanotechnology as the science, engineering, and technology science, engineering, and technology conducted at the nanoscale, which is about 1 to 100 conducted at the nanoscale, which is about 1 to 100 nanometersnanometers (nm). (nm).
Nanoscience and nanotechnology are the study and application of Nanoscience and nanotechnology are the study and application of extremely small things and can be used across all the other science extremely small things and can be used across all the other science fields, such as chemistry, biology, physics, materials science, and fields, such as chemistry, biology, physics, materials science, and engineering. Nanotechnology is not just a new field of science and engineering. Nanotechnology is not just a new field of science and engineering, but a new way of looking at and studying at the nanoscale engineering, but a new way of looking at and studying at the nanoscale where unique phenomena enable novel applications (www.nano.gov; where unique phenomena enable novel applications (www.nano.gov; accessed on 16 February 2012). accessed on 16 February 2012).
A joint report by the British Royal Society and the Royal Academy of A joint report by the British Royal Society and the Royal Academy of
Engineering similarly defined nanotechnology as “Engineering similarly defined nanotechnology as “the design, the design, characterization, production, and application of characterization, production, and application of structures, devices and systems by controlling shape structures, devices and systems by controlling shape and and size at nanometer scalesize at nanometer scale..
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The schematic figure
(a) depicts a logarithmic-length scale showing the size of a classical nanomaterial (C60 fullerene) compared with various biological components (adapted from 17). Particles of various sizes are drawn to scale.
(b) Rat macrophage cells with internalized rope-like bundles of single-walled carbon nanotubes (SWCNT). For comparison, mitochondria are marked with arrows. Human macrophages are up to two times larger than their rat counterparts.
(c) Human lung carcinoma cells with evidence of internalization of iron oxide nanoparticles of 20 nm in ∼diameter.
Source: Shvedova et al. (2010)
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Types of NPsTypes of NPs
Nanoparticle:Nanoparticle: A sub-classification of ultrafine particles with A sub-classification of ultrafine particles with lengths in two or three lengths in two or three dimensions greater than 1 nanometer (nm) dimensions greater than 1 nanometer (nm) and smaller than about 100 nm, and which may or may not exhibit size-and smaller than about 100 nm, and which may or may not exhibit size-related intensive properties.related intensive properties.
Natural nanoparticles: Natural nanoparticles: Particles with one or more dimensions at Particles with one or more dimensions at the nanoscale originating the nanoscale originating from natural processes, e.g. soil colloids.from natural processes, e.g. soil colloids.
Incidental nanoparticles:Incidental nanoparticles: Nanoparticles formed as a by-product Nanoparticles formed as a by-product of man-made or natural of man-made or natural processes, e.g. welding, milling, grinding or processes, e.g. welding, milling, grinding or combustion.combustion.
Engineered nanoparticles (less frequently also “manufactured Engineered nanoparticles (less frequently also “manufactured nanoparticles”):nanoparticles”): Nanoparticles manufactured to have specific Nanoparticles manufactured to have specific properties or a specific composition.properties or a specific composition.
Types of ENPsTypes of ENPs• FullerenesFullerenes (grouping Buckminster fullerenes, CNTs, nanocones etc.) (grouping Buckminster fullerenes, CNTs, nanocones etc.)
• Metal ENPs Metal ENPs (e.g. elemental Ag, Au, Fe)(e.g. elemental Ag, Au, Fe)
• Oxides Oxides (or binary compounds when including carbides, nitrides etc.). E.g. TiO2, (or binary compounds when including carbides, nitrides etc.). E.g. TiO2, Fe oxides.Fe oxides.
• Complex compounds Complex compounds (alloys, composites, nanofluids etc., consisting of two or (alloys, composites, nanofluids etc., consisting of two or more more elements) e.g. Cobalt-zinc iron oxide.elements) e.g. Cobalt-zinc iron oxide.
• Quantum dots Quantum dots (or q-dots) are binary or complex compounds often coated with a (or q-dots) are binary or complex compounds often coated with a polymer. They are usually regarded apart due to unique use and composition. Q-polymer. They are usually regarded apart due to unique use and composition. Q-dots are ENPs that exhibit size-dependent electronic or optical properties due to dots are ENPs that exhibit size-dependent electronic or optical properties due to quantum confinement. E.g. cadmium-selenide (CdSe) which has light emission quantum confinement. E.g. cadmium-selenide (CdSe) which has light emission peaks that varies according to particle size; green for 3 nm diameter particles, peaks that varies according to particle size; green for 3 nm diameter particles, red for 5 nm, etc. red for 5 nm, etc. Used in electronics/experimental biology/medicine.Used in electronics/experimental biology/medicine.
Animations courtesy Dr S. Dr. Maruyama; http://www.photon.t.u-tokyo.ac.jp/~maruyama/agallery/agallery.html
Properties of ENPsProperties of ENPs
• ENPs have different optical, electrical, magnetic, chemical and mechanical ENPs have different optical, electrical, magnetic, chemical and mechanical properties from their bulk counterparts are that properties from their bulk counterparts are that in this size-range (between in this size-range (between 1-100 nm) quantum effects start to predominate and the surface-area-1-100 nm) quantum effects start to predominate and the surface-area-to-volume ratio (sa/vol) becomes very largeto-volume ratio (sa/vol) becomes very large. .
• The sa/vol of most materials increases gradually as their particles become The sa/vol of most materials increases gradually as their particles become smaller, which results in ismaller, which results in increased adsorption of the surrounding atoms ncreased adsorption of the surrounding atoms and changes their properties and behaviorand changes their properties and behavior..
• Materials reduced to the nano-scale can Materials reduced to the nano-scale can suddenly show very different suddenly show very different propertiesproperties, compared to what they exhibit on the macro-scale, which enables , compared to what they exhibit on the macro-scale, which enables unique applications. unique applications.
• For example, opaque substances become For example, opaque substances become transparenttransparent (copper); stable materials (copper); stable materials become become combustible combustible (aluminum); inert materials become (aluminum); inert materials become catalysts catalysts (platinum); (platinum); insulators become insulators become conductorsconductors (silicon); solids turn into (silicon); solids turn into liquidsliquids at room at room temperature (gold) temperature (gold)
Source: Hristozov and Malsch (2009)Source: Hristozov and Malsch (2009)
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Research in nanotechnology has resulted in applications across a wide range of areas like medical and pharmaceutical sectors, the development of new materials, personal care products, to applications in agriculture and food. Today, nanoscale materials find use in a variety of different areas.
According to the Project on Emerging Nanotechnologies (PEN) over 1,300 manufacturer-identified, nanotechnology-enabled products have entered the commercial marketplace around the world and If the current trend continues, the number of products could reach 3,400 by 2020.
(http://www.nanotechproject.org/inventories/consumer; accessed on 30 January 2012)
Because of the potential of this technology there has been a worldwide increase in investment in nanotechnology research and development (Guzman et al., 2006).
The production of engineered nanoparticles (ENPs) was estimated to be 2000 tons in 2004 and is expected to increase to 58,000 tons in 2011-2020 (Maynard, 2006).
ENPs and microorganismsENPs and microorganisms
They may have an impact on soil microorganisms viaThey may have an impact on soil microorganisms via
(1) a direct effect ((1) a direct effect (toxicitytoxicity))
(2) changes in the (2) changes in the bioavailability of toxins or nutrientsbioavailability of toxins or nutrients
(3) indirect effects resulting from their (3) indirect effects resulting from their interaction with natural organic compounds interaction with natural organic compounds andand
(4) (4) interaction with toxic organic compounds interaction with toxic organic compounds which would amplify or alleviate their which would amplify or alleviate their toxicitytoxicity
While toxicity mechanisms have not yet been completely elucidated for most While toxicity mechanisms have not yet been completely elucidated for most ENPs, possible mechanisms include: ENPs, possible mechanisms include:
•disruption of membranes or membrane potential disruption of membranes or membrane potential •oxidation of proteins oxidation of proteins •genotoxicity genotoxicity •interruption of energy transduction interruption of energy transduction •formation of reactive oxygen species (ROS) andformation of reactive oxygen species (ROS) and•release of toxic constituents release of toxic constituents
[Source: Simonet and Valcárcel (2009); Klaine et al. (2008)][Source: Simonet and Valcárcel (2009); Klaine et al. (2008)]
This is a magnification of E. coli exposed to a low concentration (10 mg/L) of titanium dioxide nanoparticles. Cells with compromised membranes are stained red.
Fig. Possible mechanisms of nanomaterials toxicity to bacteria
Source: Klaine et al. (2008)
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Scanning electron microscope analysis of normal and MgF2·Nps treated cells. (a) E. coli and (b) S.aureus untreated cells after overnight growth; (c) E. coli and (d) S. aureus treated with MgF2·Nps (1 mg/ml).
Transmitted electron microscopy of MgF2·Nps treated and untreated cells. TEM micrographs of E. coli and S. aureus thin sections: Untreated E. coli (a,b) and S. aureus (c,d); MgF2·Nps (1 mg/ml) treated E. coli (e,f) and S. aureus (g,h). Arrows indicate MgF2 nanoparticles.
Source: Lellouche et al. (2009)
Source: Lyon et al. (2005) , Jia et al. (2005); Fortner et al. (2005); Lyon et al. (2008); Aoshima et al. (2009); Source: Lyon et al. (2005) , Jia et al. (2005); Fortner et al. (2005); Lyon et al. (2008); Aoshima et al. (2009); Kang et al. (2009); Zhou et al. (2005)Kang et al. (2009); Zhou et al. (2005)
Antimicrobial activity of carbon based ENPsAntimicrobial activity of carbon based ENPs
•CC6060 was harmful or has neutral biological consequences. was harmful or has neutral biological consequences.
•CC6060 aggregates inhibited aggregates inhibited Escherichia coliEscherichia coli and and Bacillus subtilis.Bacillus subtilis.
•Fullerene water suspensions Fullerene water suspensions (FWS) exhibited relatively strong antibacterial activity and were (FWS) exhibited relatively strong antibacterial activity and were more toxic to more toxic to B. subtilis. B. subtilis.
•FWSFWS exerts ROS-independent oxidative stress in bacteria, with evidence of protein oxidation, exerts ROS-independent oxidative stress in bacteria, with evidence of protein oxidation, changes in cell membrane potential, and interruption of cellular respiration.changes in cell membrane potential, and interruption of cellular respiration.
•FullerenolsFullerenols (C (C6060 (OH) 12, C (OH) 12, C60 60 (OH) 36.8H(OH) 36.8H22O, and CO, and C6060 (OH) 44.8H (OH) 44.8H22O) have been found to be toxic O) have been found to be toxic to six kinds of bacteria and two kinds of fungi. to six kinds of bacteria and two kinds of fungi.
•Carbon based ENPs like Carbon based ENPs like CNTs CNTs have been found to inactivate have been found to inactivate E. coliE. coli, , Staphylococcus epidermis, Staphylococcus epidermis, beneficial soil microbes like beneficial soil microbes like PP. . aeruginosaaeruginosa, , B. subtilisB. subtilis as well as diverse microbial communities as well as diverse microbial communities of river and waste water effluent. of river and waste water effluent.
The toxicity of CThe toxicity of C60 60 has been attributed to its ability to has been attributed to its ability to bind and deform the DNA bind and deform the DNA standsstands, thereby , thereby interfering with DNA repair mechanismsinterfering with DNA repair mechanisms..
Antimicrobial activity of metal and metal oxide ENPsAntimicrobial activity of metal and metal oxide ENPs
•Microbial toxicity has been reported for metal NPs, like Microbial toxicity has been reported for metal NPs, like elemental Ag, Au, Fe; oxides elemental Ag, Au, Fe; oxides like TiOlike TiO22, Fe-oxides, Co-Zn-Fe oxide, Fe-oxides, Co-Zn-Fe oxide etc. These NPs raise serious environmental etc. These NPs raise serious environmental concerns because of their unique dissolution properties and electronic charges, in concerns because of their unique dissolution properties and electronic charges, in addition to their small sizes and large surface-to-mass ratios (Wang et al., 2010). addition to their small sizes and large surface-to-mass ratios (Wang et al., 2010).
•Ag NP is toxic to Ag NP is toxic to E. coliE. coli and and Staphylococcus aureusStaphylococcus aureus and and B. subtilis.B. subtilis.
•Even Ag NP biosynthesized by fungi showed potent activity against fungal and Even Ag NP biosynthesized by fungi showed potent activity against fungal and bacterial strains like bacterial strains like Aspergillus nigerAspergillus niger, , StaphylococcusStaphylococcus sp. sp., , BacillusBacillus sp. sp. and and E. coliE. coli. .
•E. coliE. coli and and S. aureus S. aureus and and Pseudomonas putidaPseudomonas putida were inhibited by ENPs of Ag, CuO were inhibited by ENPs of Ag, CuO and ZnO.and ZnO.[Source: Rai et al. (2009); Suresh et al. (2010); Jaidev and Narasimha (2010); Jones et al. [Source: Rai et al. (2009); Suresh et al. (2010); Jaidev and Narasimha (2010); Jones et al.
(2008); Gajjar et al. (2009) ](2008); Gajjar et al. (2009) ]
Transmission electron micrograph of a cerium doped yttrium aluminum oxide nanoparticle.
Zn NP ZnO NP
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• Even water suspensions of nanosized titanium dioxide (TiO2), silicon dioxide (SiO2), and zinc oxide (ZnO) were found to be harmful to varying degrees, with antibacterial activity increasing with particle concentration. Antibacterial activity generally increased from SiO2 to TiO2 to ZnO, and B. subtilis was most susceptible to their effects.
• Electrospraying of NPs of NiO, CuO, or ZnO (20 nm, 20 μg, in 10 min) reduced the total number of living E. coli by more than 88%, 77% and 71%, respectively.
• ZnO, Al2O3 and TiO2 NPs were toxic to the nematode Caenorhabditis elegans inhibiting growth especially the reproductive capability.
• Likewise, oxides of Zn, Cu and Ti NPs have been reported to be toxic to the microalgae Pseudokirchneriella subcapitata.
• Exposure of earthworm (Eisenia fetida) to ZnO NPs enhanced mortality with increasing concentrations of NPs (Li et al., 2011)
Source: Adams et al. (2006); Aruoja et al. (2009); Wang et. al. (2010) Source: Adams et al. (2006); Aruoja et al. (2009); Wang et. al. (2010)
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Jason Unrine’s UK research team mixed earthworms into artificial soil tainted with gold nanoparticles. After 28 days, Unrine’s team detected gold nanoparticles throughout the earthworm’s bodies, with the highest concentrations in their gut. Some of the exposed worms produced 90 percent fewer offspring. This study can serve as a model for how organisms take up other kinds of nanoparticles.
Mechanisms of toxicity of metal ENPsMechanisms of toxicity of metal ENPs
•Pitting of the cell wall, dissipation of the proton Pitting of the cell wall, dissipation of the proton motive forcemotive force, and finally cell death (Choi et al., , and finally cell death (Choi et al., 2008). 2008).
•Ag NP would also bind with bacterial DNAAg NP would also bind with bacterial DNA, and this , and this might compromise the DNAs replication fidelity (Rai might compromise the DNAs replication fidelity (Rai et al., 2009; Yang et al., 2009). et al., 2009; Yang et al., 2009).
•These metal oxide NPs may act as ‘Trojan-Horses’, These metal oxide NPs may act as ‘Trojan-Horses’, entering cells and releasing ions intracellularlyentering cells and releasing ions intracellularly (Limbach et al., 2007).(Limbach et al., 2007).
Figure 1. left panel: Silica NPs; right panel: E. coli cells with intrenalized Si NPs
FE-SEM images of captured E. coli using anti-E. coli antibody functionalized magnetic nanoparticles 4 (a), (b), (c), and (d) four different images at different places of the sample. [Source: Rastogi et al. (2011)]
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Schematic diagram of colloidal Ag nanoparticles interaction on captured E. coli cell with NPs 4, over the period of time and observed biomolecules [Source: Rastogi et al. (2011)]
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Source: Ryabchikova, E; Mazurkova, N; Shikina, N; Ismagilov, Z; “The Crystalline Forms Of Titanium Dioxide Nanoparticles Affect Their Interactions With Individual Cells”, JMedCBR 8, 27 October 2010 [http://www.jmedcbr.org/issue_0801/Ryabchikova/Ryabchikova_Nano_10_2010.html]
Figure 2: Interaction of amorphous TiO2 nanoparticles with MDCK (Madin Darby canine kidney) culture cells. I h incubation.
A – nanoparticles fill folds and invaginations of a cell;
B - E – direct contact of the nanoparticles with cell plasma membrane;
F – invagination of plasma membrane containing nanoparticles;
G, H – nanoparticles in “coated pits”, clathrin particles are visible on the pit cytoplasmic surface;
I, J – nanoparticles in endosomes. Arrows show empty “coated pits”. Ultrathin sections. Transmission electron microscopy.
Effect on soil microorganismsEffect on soil microorganisms
•Plant growth promoting rhizobacteria (PGPR) like Plant growth promoting rhizobacteria (PGPR) like P. aeruginosaP. aeruginosa, , P.P. putida, P. putida, P. fluorescensfluorescens, , B. subtilis B. subtilis and soil N cycle bacteria and soil N cycle bacteria viz., viz., nitrifying bacteria and nitrifying bacteria and denitrifying bacteria have shown denitrifying bacteria have shown varying degrees of inhibition when exposed varying degrees of inhibition when exposed to ENPs to ENPs in pure culture conditions or aqueous suspensions (Mishra and Kumar, in pure culture conditions or aqueous suspensions (Mishra and Kumar, 2009).2009).
•Metal oxide NPs of Cu (80 to 160 nm) showed antibacterial activity against plant Metal oxide NPs of Cu (80 to 160 nm) showed antibacterial activity against plant growth promoting growth promoting Klebsiella pneumoniaeKlebsiella pneumoniae, , P. aeruginosaP. aeruginosa, , Salmonella paratyphi Salmonella paratyphi and and Shigella Shigella strains strains (Mahapatra et al., 2008). (Mahapatra et al., 2008).
•Iron and copper based NPs are presumed to react with peroxides present in the Iron and copper based NPs are presumed to react with peroxides present in the environment generating environment generating free radicals known to be highly toxic to microorganisms free radicals known to be highly toxic to microorganisms like like P. aeruginosaP. aeruginosa (Saliba et al., 2006).(Saliba et al., 2006).
Bright-field micrographs of Anabaena CPB4337 exposed to increasing concentrations of ceria nanoparticles.
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(A) Control Anabaena filaments.
(B and C) Anabaena filaments exposed to 1 mg/l N10 for 48 h and 80 mg/l N10 for 72 h.
(D, E, and F) Anabaena filaments exposed to 0.1 mg/l N25 for 72 h, 1 mg/l N25 for 24 h, and 80 mg/l for 24 h.
(G and H) Anabaena filaments exposed to 0.01 mg/l N50 for 48 h and 50 mg/l N50 for 48 h.
(I, J, and K) Anabaena filaments exposed to 1 mg/l N60 for 24 h, 50 mg/l N60 for 72 h, and 80 mg/l N60 for 24 h. Bars, 20 μm.
P.S. Anabaena is a genus of filamentous cyanobacteria that exists as plankton. It is known for its nitrogen fixing abilities in submerged / paddy soils, and they form symbiotic relationships with certain plants, like Azolla)
Published literature on the effects of ENPs on soil microorganismsPublished literature on the effects of ENPs on soil microorganisms
ENP Effects Source
Carbon containing
fullerenes/ CNTs
No inhibition in the activity of dehydrogenase and activities of
enzymes involved in N (urease), P (acid-phosphatase) and C (β-
glucosidase) cycles in the soil. A slight shift in bacterial DNA,
indicating a minor change in the community structure measured
using PCR-DGGE. (Incubation study)
Tong et al.
(2007)
Number of fast-growing bacteria decreased by three-to four
folds immediately after incorporation of the C60 and protozoan
number decreased only slightly in the beginning of the experiment.
A slight shift in bacterial DNA, indicating a minor change in the
community structure measured using PCR-DGGE. (Incubation
study)
Johansen et
al. (2007)
No significant effect on the anaerobic community of biosolids
from anaerobic wastewater treatment sludge over an exposure
period of a few months. No change in methanogenesis and no
evidence of substantial microbial community shifts due to treatment
with C60. (Microcosm study)
Nyberg et al.
(2008)
Multi-walled CNT significantly inhibited the activities of 1,4-β-
TiO2- and ZnO-NPs significantly inhibited soil protease,
catalase, and peroxidase activities; urease activity was
unaffected. (Field study)
Du et al.
(2011)
Zn- and ZnO-NPs inhibited the activities of dehydrogenase,
β -glucosidase and acid phosphatase in soils. (Pot study)
Kim et al.
(2011)
Ag-, Cu- and Si-NPs impacted arctic soil bacterial community;
Ag-NPs were highly toxic to a plant beneficial bacterium,
Bradyrhizobium canariense. (Incubation study)
Kumar et al.
(2011)
(Source: Dinesh et al. (2012)
MNPs
1
23
4
5
1. Dissolution2. Sorption/aggregation3. Plant bioaccumulation4. Invertebrate accumulation and toxicity5. Microbial toxicity6. Direct particle uptake/toxicity7. Particle migration
6
7
Dissolvedpool
Fig. Key processes in soil relating to transformation and Fig. Key processes in soil relating to transformation and potential risk from manufactured nano particles (MNPs; Source: potential risk from manufactured nano particles (MNPs; Source: Klaine et al. (2008)Klaine et al. (2008)
ConclusionsConclusions
• The anti-microbial activity of metal NPs to soil microbial communities holds great significance.
• Little information is available on how metal ENPs act in the soil matrices especially their adsorption to clay minerals, organic fractions, toxic substances, organic pollutants etc.
• More information is needed on interaction of ENPs with soil components and more quantitative assessments of aggregation/ dispersion, adsorption/ desorption, precipitation/ dissolution, decomposition, and mobility of ENPs in the soil environment is essential.
• Overall, it is apparent from the studies done in vitro that ENPs pose a potential hazard to microorganisms.
• Studies done by incubating soils with ENPs, microcosm studies and pot experiments suggests that in most cases ENPs inhibit soil microbial activity.
• This underlines the fact that the effects of ENPs on microbial community in soils under field conditions is still in its infancy, the smothering effects of SOM and HA on ENPs are still being speculated and the bacterial self protection-mechanism on encountering ENPs in the soil matrix is yet to be extensively studied.
• Considering that attempts are being made to employ some of these ENPs as carrier materials for smart delivery of chemical fertilizers and pesticides to crops, (DeRosa et al., 2010) it is imperative that we set specific standards for the manufacture, use, and disposal of ENPs.
• Therefore, conclusive evidences need to be obtained to draw strong conclusions about the potential toxicity of ENPs to microbial activity under field conditions and herein lies one of the main challenges in environmental risk assessment of spreading ENPs.
However, before these advantages can come into play, However, before these advantages can come into play, the risks of the risks of NPs for the environment and crops have to be definedNPs for the environment and crops have to be defined to ensure their sustainable and beneficial application.to ensure their sustainable and beneficial application.
Relevant ecotoxicological information on exposure and effects of NPs as Relevant ecotoxicological information on exposure and effects of NPs as a basis for a a basis for a comprehensive risk assessment comprehensive risk assessment is needed.is needed.
(Source: Bucheli TD- (Source: Bucheli TD- Effects of NANOparticles on beneficial soil MIcrobes and CROPS Effects of NANOparticles on beneficial soil MIcrobes and CROPS (NANOMICROPS); (NANOMICROPS); http://www.nfp64.ch/E/projects/environmental_research/effects_nanoparticles_michttp://www.nfp64.ch/E/projects/environmental_research/effects_nanoparticles_microbes_crops/Pages/default.aspx; accessed on 28/2/20120)robes_crops/Pages/default.aspx; accessed on 28/2/20120)
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An Engineered Nano Particle Risk Assessment (ENPRA) Approach
ENPRA aims at developing and implementing a novel integrated approach for ENP Risk Assessment. This approach is based on the Exposure-Dose-Response Paradigm for ENP (see figure below).
•This paradigm states that exposure to ENP of different physico-chemical characteristics via inhalation, ingestion or dermal exposure is likely to lead to their distribution, beyond the portal-of-entry organ to other body systems.
•The cumulative dose in a target organ will eventually lead to an adverse response in a dose-response manner.
[Source: http://www.mapfre.com/fundacion/html/revistas/seguridad/n114/articulo1En.html; accessed on 29/02/2012]
The approach proposed by ENPRA is in line with the grand challenges described by Maynard et al. (2006). The rationale of ENPRA is summarised graphically in the below figure .
Nanotechnology Nanotechnology has not yet been provenhas not yet been proven to be safe for humans or for the environment.to be safe for humans or for the environment.
Oxford University and Montreal University linked titanium dioxide and zinc oxide nanoparticles in Oxford University and Montreal University linked titanium dioxide and zinc oxide nanoparticles in sunscreen to causing sunscreen to causing free radical and DNA damage free radical and DNA damage in skin. And numerous other studies have in skin. And numerous other studies have found that nanoparticles are easily absorbed by cells, where they cause other untold harm within the found that nanoparticles are easily absorbed by cells, where they cause other untold harm within the body.body.
Nanoparticles have been found to cause Nanoparticles have been found to cause brain damage in fish and other aquatic species brain damage in fish and other aquatic species exposed to them.exposed to them.
ENPs have been found to be ENPs have been found to be toxic to microorganismstoxic to microorganisms. .
Possible toxicity mechanisms include Possible toxicity mechanisms include •disruption of membranes or membrane potentialdisruption of membranes or membrane potential•oxidation of proteins,oxidation of proteins,•genotoxicity, genotoxicity, •interruption of energy transductioninterruption of energy transduction•formation of reactive oxygen species and formation of reactive oxygen species and •release of toxic constituentsrelease of toxic constituents•structural changes to the microbial cell surface that may eventually lead to cell death. structural changes to the microbial cell surface that may eventually lead to cell death.
'The key question therefore is how to benefit from nanotechnologies while 'The key question therefore is how to benefit from nanotechnologies while limiting these risks?'limiting these risks?'
One suggestion is to ‘One suggestion is to ‘take into account the ethical, health, environmental and take into account the ethical, health, environmental and regulatory considerations linked to nanotechnologies regulatory considerations linked to nanotechnologies as early on as possible in as early on as possible in the R&D phase, and to encourage dialogue with the public’. the R&D phase, and to encourage dialogue with the public’.
The aim is to ‘The aim is to ‘spark debate early on among all those concerned so as to avoid spark debate early on among all those concerned so as to avoid repeating the mistakes made with genetically modified organisms repeating the mistakes made with genetically modified organisms (GMOs) (GMOs) where the public were reluctant to accept anything mildly related to GMOs’ where the public were reluctant to accept anything mildly related to GMOs’ ((Stephen Stephen Schaller, EU funded Nanologue project)Schaller, EU funded Nanologue project)..(Source: ‘(Source: ‘Dissecting the pros and cons of nanotechnologies’ at Dissecting the pros and cons of nanotechnologies’ at http://cordis.europa.eu/fetch? http://cordis.europa.eu/fetch?CALLER=NEWSLINK_EN_C&RCN=26524&ACTION=D) accessed on 28/2/2012)CALLER=NEWSLINK_EN_C&RCN=26524&ACTION=D) accessed on 28/2/2012)
Further reading : Dinesh, R., Anandaraj, M., Srinivasan, V., Hamza, S., 2012. Engineered nanoparticles in the soil and Further reading : Dinesh, R., Anandaraj, M., Srinivasan, V., Hamza, S., 2012. Engineered nanoparticles in the soil and their potential implications to microbial activity. Geoderma 173-174, 19-27.their potential implications to microbial activity. Geoderma 173-174, 19-27.
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Aoshima, H., Kokubo, K., Shirakawa, S., Ito, M., Yamana, S., Oshima, T., 2009. Antimicrobial activity of fullerenes and their hydroxylated derivatives. Biocontrol Sci. 14, 69-72.
Aruoja, V., Dubourguier, H.C., Kasemets, K., Kahru, A., 2009. Toxicity of nanoparticles of CuO, ZnO and TiO2 to microalgae Pseudokirchneriella subcapitata. Sci. Total Environ. 407, 1461-1468.
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