Nanotoxicology small particles with unique toxicity
from aquatic to
human model systems
Tara Sabo-Attwood, PhD
University of South Carolina
NCSU Workshop on
Communicating 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”…
Challenges of assessing environmental exposures
Complex webs and networks
If nanoparticle X moves from consumer product
to soil to groundwater
countless scenarios of how these
particles could impact drinking water
How to study safety of nanomaterials?
Nature 444, 267-269 (16 November 2006), Safe handling of nanotechnology
Andrew D. Maynard et al.
“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”.
Public perceptions are not static
Fundamental Knowledge of the
Environmental Impacts of Nanomaterials
Effects of Environment and
Living Systems on
Nanomaterials
Effects of Nanomaterials on
the Environment and Living
Systems
Fate and Transport
Aggregation
Surface Change
Adsorption
Partitioning
Compartment Modeling
Bioaccumulation
Biomagnification
Biodiversity
Metabolism, Reproduction
Quality of Life
Food Web Modeling
Nanomaterial Production, Standard Reference Materials, Analytical Methods
to detect Nanomaterials in the Environment and Living Systems
RISK ASSESSMENT
Public influences risk management and
toxicological science
Public
toxicological science
(which particles, fate,
transport, route etc)
Risk assessment/management
Lung epithelial cells exposed to SWNT
A number of genes altered are involved in cell
cycle regulation and mitochondrial/electron
transport function
Some are similar to gene changes observed
with asbestos
Electron transport genes altered
Cell cycle genes altered
# of genes altered by asbestos
27
32
55
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
Gold nanoparticles - biologically inert?
Mechanisms of toxicity – gene profiling
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
Leaves
734
28
96
Roots
But no metallothionein, wound or
pathogen response genes
Gold nanoparticles - biologically inert?
Aspect
ratio
AR=2.1
AR=2.6
AR=2.9
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=3.4
AR=4.1
100
Effective surface charge (mV)
80
% cell viability
AR=1
60
40
20
0
CTAB
safe particles by design?
PAA
PAH
What about particle synthesis byproducts?
• 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?
n=17
n=87
n=68
n=73
n=80
n=84
n=83
n=90
n=85
n=90
n=80
n=92
n=81
n=59
120
n=93
Effects of SWNT on copepod nauplius – adult
development
% Development
100
80
*
*
*
60
*
40
*
20
0
0
AP-SWNT
0.58
0.97
1.6
Nanocarbon Concentration (mg L-1)
Pure SWNT
10
Fluorescent nanocarbon
Do ‘new’ materials influence toxicity of
‘old’ materials
10 mg L-1 SWNT in 10 mM phosphate
buffer/synthetic seawater solution (pH 7.8)
Napthalene
Cs (mol/kg)
10000
0 ppt
Carbon Solutions SWNT
Synthetic SWNT
NIST SRM 2975 soot
1000
100
25 ppt
10
1e-5
1e-4
1e-3
Cw (M)
1e-2
1e-1
Bioavailability factors for PCBs and
PBDEs
NT+HOC
Soot+HOC
n=3
2.0
HOC Only
1.8
n=3
Theoretical BSAF (1.72)
n=3
1.6
0.6
n=1
0.8
n=1
1.0
*
n=2
1.2
n=1
n=2
*
n=3
BSAFs
1.4
0.4
0.2
0.0
0
0
PCB 52
0
0 0
PCB 95
0 0 0
PCB 77
0
PCB 118
BDE 47
BDE 99
Congener
Error bars represents ±1 sd. Significant differences relative to HOC only treatment are denoted with an *
Unusual effects
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.
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 complex
than 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?
Risk Communication
Risk Communication
Risk
Assessment
Risk
Management
Regulatory
Process
Risk
Regulatory
Characterization Decision
SCIENCE
“informing the public and
involving them in the risk
assessment and risk
management processes.”
Adapted from http://www.envirotools.org/presentations/ppt_riskcommunication.htm
REGULATIONS
Acknowledgements
Nanoenvironmental
Team
Gene Feigley
Shosaku
Kashiwada
Tom Chandler
Lee Ferguson
Sean Norman
Alan Decho
John Ferry
Cathy Murphy
Research Triangle Institute
(RTI) and Dr. Wally Scrivens
(USC Dept. of Chemistry):
14C-SWNT synthesis
collaboration
Funding: EPA STAR, NSF, USC
research foundation