Nanotoxicology - small particles with unique toxicity

from aquatic to human model systems

Tara Sabo-Attwood, PhDUniversity of South Carolina

NCSU Workshop onCommunicating Health and Safety Risks on

Emerging Technologies

Today’s talk(from an environmental molecular

toxicologist point of view)

Nanomaterials in the environment – challenges of assessing unintended exposures

Influence of public perception on science

What have we learned? Unexpected effects

Nanomaterials Represent a Novel Form of Contaminants in the Environment

Not a question of “IF” but

“WHEN” & “WHAT”…

Complex webs and networks

Challenges of assessing environmental exposures

If nanoparticle X moves from consumer product to soil to groundwater

countless scenarios of how theseparticles could impact drinking water

Nature 444, 267-269 (16 November 2006), Safe handling of nanotechnologyAndrew D. Maynard et al.

How to study safety of nanomaterials?

Public perceptions are not static

“Communicating research on nanotechnology risks and benefits outside the scientific community is challenging, but is essential for a risk dialogue based on sound science. This means developing communication activities that enable technical information to be summarized, critiqued and ultimately synthesized for various interested parties, including decision-makers and consumers. The advent of the Internet provides an ideal venue for such activities and we encourage its use in communicating with the end-users of risk-based science”.

Fundamental Knowledge of the Environmental Impacts of Nanomaterials

Effects of Environment and Living Systems on

Nanomaterials

Fate and TransportAggregation

Surface ChangeAdsorptionPartitioning

Compartment Modeling

Effects of Nanomaterials on the Environment and Living

Systems

BioaccumulationBiomagnification

BiodiversityMetabolism, Reproduction

Quality of LifeFood Web Modeling

Nanomaterial Production, Standard Reference Materials, Analytical Methodsto detect Nanomaterials in the Environment and Living Systems

RISK ASSESSMENT

Public influences risk management and toxicological science

toxicological science(which particles, fate,transport, route etc)

Risk assessment/management

Public

A number of genes altered are involved in cell cycle regulation and mitochondrial/electrontransport function

Some are similar to gene changes observed with asbestos

Electron transport genes altered 27Cell cycle genes altered 32# of genes altered by asbestos 55

Lung epithelial cells exposed to SWNT

Which nanoparticles are toxic and which are not? If so, what inherent properties govern toxicity?

Challenge – not all scientists agree(impact trust, perceived benefit etc)

What have we learned so far? Are gold nanoparticles biologically inert? Plants and human cells exposed to gold nanoparticles

toxicity of synthesis byproducts - marine invertebrates (copepods) and human cells exposed to SWNT

Subtle unusual effects - freshwater fish (medaka) exposed to silver nanospheres

Gold nanoparticles - biologically inert?

Tobacco seedlings were exposed to gold nanospheres (3.5 or 18 nm)

3.5 nm spheres were taken up via roots and distributed throughout plant

Tomato plants exposed to 3.5 nm gold spheres for 5 days. Microarrays performed on leaves and roots.

Results: Leaves with at least 2-fold change in expression between control and exposed

Roots with at least 2-fold change Common genes to leaves and roots

734 9628

Leaves

Roots

But no metallothionein, wound or pathogen response genes

Mechanisms of toxicity – gene profiling

Gold nanoparticles - biologically inert?

Aspect ratio

Effective surface charge (mV)

CTAB-capped PAA-coated

4.1 + 41.32 ±0.9 - 41.32 ±0.9

3.4 + 40.02 ±0.7 - 39.55 ± 0.9

2.9 + 47.77 ±0.6 - 40.25 ±1.02

2.6 + 39.92 ±1.1 - 47.21 ±0.8

2.1 + 43.23 ±0.8 - 38.01 ±1.1

1 + 39.22 ±0.6 - 44.08 ±1.05

AR=1 AR=2.1 AR=2.6 AR=2.9 AR=3.4 AR=4.1

Gold nanoparticles - biologically inert?

0

20

40

60

80

100

% c

ell

via

bili

ty

CTAB PAA PAH

safe particles by design?

• SWNTs– Electrophoretic Purification (Xu et al.,

2004)• Purified SWNTs: nominal molecular

weight (NMW) >100K• Short tubular nanocarbon: NMW =

50K – 100K• Fluorescent Nanocarbon: NMW =

12.5K – 50K

What about particle synthesis byproducts?

0

20

40

60

80

100

120

0 0.58 0.97 1.6 10

n=59

n=90

n=90

n=80

n=87

n=93

n=92

n=85

n=84

n=68

n=81

n=80

n=83

n=73

% D

evel

op

men

t

n=17

*

*

***

Nanocarbon Concentration (mg L-1)

AP-SWNT Pure SWNT Fluorescent nanocarbon

Effects of SWNT on copepod nauplius – adult development

What about particle synthesis byproducts?

0 ppt 25 ppt

10 mg L-1 SWNT in 10 mM phosphate

buffer/synthetic seawater solution (pH 7.8)

Cw (M)

1e-5 1e-4 1e-3 1e-2 1e-1

Cs

(m

ol/k

g)

10

100

1000

10000

Carbon Solutions SWNTSynthetic SWNTNIST SRM 2975 soot

Napthalene

Do ‘new’ materials influence toxicity of‘old’ materials

Bioavailability factors for PCBs and PBDEs

Error bars represents ±1 sd. Significant differences relative to HOC only treatment are denoted with an *

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

PCB 52 PCB 95 PCB 77 PCB 118 BDE 47 BDE 99

Congener

BS

AF

s

NT+HOC Soot+HOC HOC Only

*

*

0000000 00

n=1 n=

2n=1

n=2

n=1

n=3

n=3

n=3

n=3

Theoretical BSAF (1.72)

Freshwater fish (Medaka) exposed to silver nanospheres

• Fish embryos were exposed in water to 10 ppm silver-colloid nanoparticles (4 nm diameter, commercially available)

• After 5 hours, the embryo architecture is completely destroyed

• Environmental concentrations will likely be 50-1000 times lower.

Unusual effects

Age-Dependent Toxic Effects of Ag-Nanocolloids in Medaka Embryos.Embryo stage Stage 11 Stage 21 Stage 30

Ag-nano (mg/L) 0 0.5 1.0 0 0.5 1.0 0 0.5 1.0

Inhibition of Blood vessels

- - + - + + - - +

Blood clot (%) 0 0 0.6 0 0 13.3* 0 0 0

Percardiovascular edema and tubular heart (%)

0 0 0 0 10.0* 0 0 0 3.3

Heart beat (15 sec) 29.1 29.8 NA 29.5 30.0 31.0 31.7 30.2 30.3

Hatch ratio (%) 93.3 70.0 0 100 56.7* 3.3 100 100 43.3*

Hatch error (%) 0 0 NA 0 0 0 0 0 3.3

Spinal deformity (%)

0 3.3 NA 0 23.3* 0 0 3.3 26.7*

Hatch time (day) 9.0 8.4 NA 9.0 8.6 9.0 8.0 8.7 9.7

*ANOVA P<0.05.

What does all this mean (as toxicologists)?

Our understanding of the potential toxic effects of nanomaterials is more complexthan originally thought

Daunting challenge – so may nanomaterials, byproducts etc classic toxicological paradigms need to shift to a more interdisciplinary approach including modeling and forcasting

But how do we do this?

How will this effect risk communication?

RiskRiskAssessmentAssessment

RiskRiskManagementManagement

RegulatoryRegulatoryProcessProcess

Risk CommunicationRisk Communication

SCIENCESCIENCEREGULATIONSREGULATIONS

Risk Risk CharacterizationCharacterization

RegulatoryRegulatoryDecisionDecision

Risk Communication

Adapted from http://www.envirotools.org/presentations/ppt_riskcommunication.htm

“informing the public and involving them in the risk assessment and risk management processes.”

Lee Ferguson John Ferry Cathy Murphy

Tom Chandler Alan Decho

Gene Feigley Shosaku

Kashiwada

Sean Norman

Nanoenvironmental Nanoenvironmental TeamTeam

Research Triangle Institute (RTI) and Dr. Wally Scrivens (USC Dept. of Chemistry): 14C-SWNT synthesis collaboration

Funding: EPA STAR, NSF, USC research foundation

Acknowledgements