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Application of ADME/PK Studies to Improve Safety Assessments for Food and Cosmetics
February 23, 2015
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Consideration of ADME/PK in Safety Assessments for Engineered Nanomaterials: Example with Silver Nanoparticles
William K. Boyes, PhD. Office of Research and Development US Environmental Protection Agency Research Triangle Park, NC
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Dr. Boyes has no financial conflicts of interest The materials in this presentation do not represent endorsement of commercial products or official policies of the Environmental Protection Agency
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What is nanotechnology?
Nanotechnology is science, engineering, and technology conducted at the nanoscale
Nanoparticles are usually defined as having at least 1 dimension between 1 to 100 nanometers.
1 nm = 10-9 m 1 nm x 109 = 1 m 1 m x 107 = size of earth
Visible Earth (http://visibleearth.nasa.gov/)
“There is plenty of room at the bottom” (Richard Feynman)
meters
10-9 10-7 10-5 10-3 10-1 101 103 105 107 109
1 nm 100 nm
90 nm size of HIV 200 nm = 2 x 10-7 m (limit visible microscope) 400-700 nm, wavelengths of visible light
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Nanotechnology is growing
President’s Council of Advisors on Science and Technology, 2014
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Categories of commercial nanomaterials
Category # product listings
Examples
Carbon nanotubes 714 SWCNT, MWCNT
Fullerenes 136 Pure or functionalized
Graphene 38 Film, on substrate
Nanoparticles of elements 549 Metals (silver, gold etc.)
Binary compounds 750 metal oxides, salts, carbonates
Complex compounds 205 Doped metal oxides
Quantum Dots 183 Cadmium selenide
Biomedical Quantum Dots 205 Peg modified Qdots, Antibody coated
Nanowires 26 Copper, gold, indium
Nanofibers 30 Carbon
Non-carbon nanowires 1 Titania
6 http://www.nanowerk.com/phpscripts/n_dbsearch.php Accessed Aug 6, 2012
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Health and Safety Issues for Engineered Nanomaterials (ENM)
High surface area / mass causes high reactivity High reactivity may lead to inadvertent toxicity Small size may enable them to distribute widely in biological
systems Evaluating ENM risks will require methods and technology
beyond traditional toxicological tools Rapid development and application exceeds capacity to test
potential toxicity using conventional approaches Risk assessments will need to consider:
– alternative testing strategies (ATS) – in vitro - in vivo extrapolation (IV-IVE)
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Transformative Science
Toxicity Testing in the 21st Century: A Vision and a Strategy (NRC, 2007)
Growing number of ENM; can’t afford to test one-by-one Behavior of ENM depends on their inherent chemical and
physical properties and how those properties interact with the environment and sensitive species in the environment
Transformative science will understand the influence of ENM material properties and build predictive models so that each new material does not need to be fully tested
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Chemical Safety for Sustainability
Developing test systems that are adequate for evaluation of nanomaterials
Identifying critical parameters that influence their behavior in the environment
Determining how the inherent properties influence behavior in biological systems and act in adverse outcome pathways
Objectives: Emerging Materials/ Nanomaterials
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Research Approach
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Nano-silver (AgNP) Uses & Misuses
Fabric coatings Surface coatings Spray disinfectants Children’s products Electronics Household appliances Water disinfectants Medical wrappings and
devices Food packaging Food supplements
“Homeopathic remedies” colloidal silver products
– Dietary supplements – Inhalant formulations – Skin products
FDA (1999): – NOT safe and effective – Side effects include:
Argyria (blue-gray skin) Poor absorption of drugs Possible kidney, liver, or
nervous system problems
Anti-microbial properties (AgNP release Ag+ )
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Silver Nanomaterials
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Release of Silver from Nanotechnology-Based Consumer Products for Children • Examined bioavailable silver released from products for
children • Among liquid media, sweat and urine caused the largest
amount of silver to be released • Fabrics, plush toys and spray products were most likely to
release silver • Dissolution of silver particles to ionic form facilitated exposure • Overall, however, the level of exposure to children from
consumer products was predicted to be low
Released from Products
Fate Transport & Transformation
Health Effects
Ecological Effects
Comprehensive Analysis QUADROS, M. E., PIERSON, R., TULVE, N. S., WILLIS, R., ROGERS, K., THOMAS, T. A. & MARR, L. C. 2013. Environmental Science & Technology, 47, 8894-8901.
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Silver Nanomaterials
Silver speciation and release in commercial antimicrobial textiles as influenced by washing • The speciation of silver in commercial textiles as revealed by
XANES, is complex • Silver nanoparticles are only one of several Ag species in
commercial textiles (Ag(0), AgCl, Ag2S, Ag–phosphate, ionic Ag and other species)
• Washing with two detergents resulted in significant changes in silver speciation (Ag-phosphates, nitrates and sulfates)
• The complexity of Ag speciation in textiles complicates exposure assessments
Released from Products
Fate, Transport & Transformation
Health Effects
Ecological Effects
Comprehensive Analysis
LOMBI, E., DONNER, E., SCHECKEL, K. G., SEKINE, R., LORENZ, C., GOETZ, N. V. & NOWACK, B. 2014.. Chemosphere, 111, 352-358.
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Silver Nanomaterials
Alterations in physical state of silver nanoparticles exposed to synthetic human stomach fluid • Acidic conditions in synthetic stomach fluid altered the
physical and chemical state of silver nanoparticles
• Citrate-stabilized AgNPs agglomerate and form AgCl during exposure to simulated stomach fluid.
• Ingested AgNPs may be converted to a variety of aggregated and chemically modified particles in the stomach
Released from Products
Fate, Transport & Transformation
Health Effects
Ecological Effects
Comprehensive Analysis
ROGERS, K. R., BRADHAM, K., TOLAYMAT, T., THOMAS, D. J., HARTMANN, T., MA, L. & WILLIAMS, A. 2012. Science of The Total Environment, 420, 334-339.
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Silver Nanomaterials
Investigating oxidative stress and inflammatory responses elicited by silver nanoparticles using high-throughput reporter genes in HepG2 cells: effect of size, surface coating, and intracellular uptake. • Silver nanoparticles and silver nitrate activate same cellular
stress-response and inflammatory pathways
• Smaller nanoparticles are more potent than larger particles
• Effects of silver nanoparticles likely mediated by silver ions
Released from Products
Fate, Transport & Transformation
Health Effects
Ecological Effects
Comprehensive Analysis
PRASAD, R. Y., MCGEE, J. K., KILLIUS, M. G., SUAREZ, D. A., BLACKMAN, C. F., DEMARINI, D. M. & SIMMONS, S. O. 2013. Toxicol In Vitro, 27, 2013-21
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Silver Nanomaterials
Released from Products
Fate, Transport & Transformation
Health Effects
Ecological Effects
Comprehensive Analysis
Toxicogenomic Responses of Nanotoxicity in Daphnia magna Exposed to Silver Nitrate and Coated Silver Nanoparticles • Daphnia showed different genomic responses to silver nitrate
and silver nanoparticles • Silver nanoparticles disrupted protein metabolism and signal
transduction • Silver nitrate downregulated developmental processes,
particularly in sensory systems
POYNTON, H. C., LAZORCHAK, J. M., IMPELLITTERI, C. A., BLALOCK, B. J., ROGERS, K., ALLEN, H. J., LOGUINOV, A., HECKMAN, J. L. & GOVINDASMAWY, S. 2012. Environmental Science & Technology, 46, 6288-6296.
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Silver Nanomaterials Comprehensive Environmental Assessment (CEA) 2012 • a framework for systematically organizing complex information
• a process of collective judgment to evaluate information and
identify research gaps.
Released from Products
Fate, Transport & Transformation
Health Effects
Ecological Effects
Comprehensive Analysis http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=241665
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3771750/bin/ijn-8-3365Fig1.jpg Gerald Bachler, Natalie von Goetz, and Konrad Hungerbühler. A physiologically based pharmacokinetic model for ionic silver and silver nanoparticles. Int J Nanomedicine. 2013; 8: 3365–3382.
PBPK model for silver ion and silver NP Bachler et al 2013
Model Rat and
human Ag+ and
AgNP 3 routes of
exposure Fit to data
from literature
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PBPK model for silver ion and silver NP Bachler et al., 2013
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3771750/bin/ijn-8-3365Fig2.jpg Gerald Bachler, Natalie von Goetz, and Konrad Hungerbühler. A physiologically based pharmacokinetic model for ionic silver and silver nanoparticles. Int J Nanomedicine. 2013; 8: 3365–3382.
Ionic Silver Nanoparticle Silver
MPS – mononuclear phagocyte system
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3771750/bin/ijn-8-3365Fig4.jpg Gerald Bachler, Natalie von Goetz, and Konrad Hungerbühler. A physiologically based pharmacokinetic model for ionic silver and silver nanoparticles. Int J Nanomedicine. 2013; 8: 3365-3382.
Simulations vs rat oral 28 day exposure
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3771750/bin/ijn-8-3365Fig6.jpg Gerald Bachler, Natalie von Goetz, and Konrad Hungerbühler. A physiologically based pharmacokinetic model for ionic silver and silver nanoparticles. Int J Nanomedicine. 2013; 8: 3365–3382.
Simulations vs human data
Model fit to data from: A. Deceased normal adults B. Burn patients treated with silver nitrate C. Occupational exposure with silver in air
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Gerald Bachler, Natalie von Goetz, and Konrad Hungerbühler. A physiologically based pharmacokinetic model for ionic silver and silver nanoparticles. Int J Nanomedicine. 2013; 8: 3365–3382.
Particle size, surface charge and coating had a minor influence on distribution due to opsonization and corona stabilization
More likely for AgNP to be stored as insoluble salt particles than dissolve into Ag+ in vivo. No significant dissolution in vivo
Mononuclear phagocyte system plays a minor role at relevant exposure levels for human consumers
Conclusions from PBPK model
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In vitro nanotoxicology considerations Physical/chemical
characterization of particles Suspension / dispersion
protocols Stability of suspensions over
time Agglomeration / transformation Assay measurements &
interference with luminance, fluorescence or colorimetric assays (e.g. MMT)
Dose metric (e.g.) – Mass concentration (ug/ml, or
ppm) – Mass / surface area of well
(ug/m2) – # particles – Surface area of particles (m2/g) – Delivered dose to cells
(estimated) – Delivered dose to cells
(measured)
(in addition to normal considerations for in vitro – in vivo extrapolation (IV – IVE))
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ToxCast HTS assay data to classify nanomaterials based biological activity
Problem – Many more ENM are being developed than can be tested with existing approaches – High Throughput Screening (HTS) is being developed for chemicals: will it work for
ENM? Approach
– Evaluate a variety of ENM using the ToxCast assays – Select nanomaterials that range across composition size and structure – Evaluate outcomes as they map to classes and types of ENM
Deliverables – Data set has been collected and will be available – Analysis is complex and underway. Impact – Decisions and approaches to screening novel ENM – Ranking and classification of ENM by profile of outcomes – Prioritization for further assessment
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Screening diverse classes of NMs in ToxCast
* IAT NP and IAT NP infused with Ag ion # purified sample with no/low ions Not listed: Dispersant of one of the nano-Ag
DNA
RNA
Protein
Function/ Phenotype
Screened 67 samples (62 unique) Endpoint types by platforms
• Transcription factor activation
• Protein profile
• Cell growth kinetics
• Toxicity phenotype
• Developmental malformation (zebrafish)
nano micro ion Ag 5+2* 1 1 Asbestos 3 Au 1 CNT 8 CeO2 4 1 1 Cu 4+2# 2+1# 2 SiO2 5 1 TiO2 9 4 ZnO 2 1 1
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Overview of ToxCast Screening of 62 Nano and Reference Materials
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Individual particles
Yellow: Less active Blue: More active Groups of
assays
Bioactivity generally in the 1-100 ug/ml range NM with Ag, Cu, Zn are more active than others Data are being analyzed NT & asbestos had different inflammatory response profiles
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Further in vitro studies
Evaluate – The role of particle size and coating – Measures of cellular uptake & distribution – Measures of cellular dose
Model – Human derived retinal pigment epithelial cells (APRE-19) – Suspend in cell culture medium (containing protein) – Treat cells for 24 hrs – Evaluate uptake of AgNP and cytotoxicity
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Silver Samples Analyzed 75nm PVP 50nm PVP 10nm PVP
10nm Citrate 50nm Citrate
50 nm 10 nm
25 nm 50 nm 100 nm
75nm Citrate
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Silver nanoparticle cytotoxicity
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• Cytotoxicity of silver nanoparticles evaluated in human derived retinal pigment epithelial cells (ARPE-19)
• Small particles more toxic than large particles
• PVP coating more toxic than citrate coating in larger sized particles
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Silver nanoparticles in ARPE-19 cells in culture under dark field / fluorescence microscopy
Blue: DNA Green: Golgi White: AgNP Orange: Cell Membrane
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Zucker et al., 2013
Blue: DNA Green: Golgi White: AgNP Orange: Cell Membrane
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Flow-cytometry Cells that incorporate
reflective ENM will show – Increased side scatter (SSC) – Reduced forward scatter (FSC)
SSC is a function of – ENM particle size – ENM particle number
AgNP show increased far red fluorescence from Surface Plasmon Resonance
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Zucker et al., 2013
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Target cell dosimetry in vitro
cell layer
media
Size (nm)
1 10 100 1000
Diffusion Sedimentation
Particle deposition influenced by: • Size • Agglomeration • Density • Media
• Viscosity • Density • Temperature
• Time • ISDD Model
• Stokes Law (sedimentation)
• Stokes-Einstein Equation (diffusion)
• Refs: • Teeguarden et al, 2007 • Hinderliter et al., 2010 • Cohen et al., 2103
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ICP-MS Flow cytometry
No Cells
20 nm AG NP
0.25 mls
cells
cells
cells0.25 mls
0 ug/ml
3 ug/ml
30 ug/ml
ARPE-19 Cells
Cells
pellet
Into 2 flasks3 ug/ml
Into 2 flasks
Into 2 flasks10 ug/ml
0 ug/ml
30 mg/ml
10 ug/ml
300 ulsupernat
Media and wash
300 ul / flash for each flask
[Ag] in cells and media
APRE-19 cells in vitro AgNP (citrate), control and 3
concentrations After 24 hrs., separate cells from
media Measure [Ag] in cells & media
via ICP-MS Compare flow side-scatter with
ICP-MS Do with both 20 nm and 75 nm
AgNP
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[Ag] in Media and Cells by ICP-MS
• After 24 hours, as much as 90% of silver remains in the media
• Smaller ENM are the more likely to remain dispersed in media
• Dose level (ug/ml) added to the culture can be very different from actual dose to the cell layer for adherent cell cultures
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Dose measures compared
• Measures of dose include: • mass • particle number • surface area
• Vary greatly across particle size • In some cases are inversely
correlated
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Flow Cytometry Side Scatter vs Dose
• Side scatter is linearly related to measures of absorbed dose
• Relationship varies with particle size • Side scatter could be used as a rapid
and inexpensive measure of cellular dose if pre-calibrated for particle size and composition
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Conclusions
Expanding development and use of nanomaterials requires new approaches for safety and risk evaluations
Alternative testing data with pharmacokinetic information promises to be increasingly important
In vitro dose metrics and dosimetry models are critical for evaluating in vitro toxicity data
AgNP vs Ag+
– Many (but perhaps not all) toxic actions of AgNP are related to Ag+
– AgNP may be accessible to pharmacokinetic compartments unavailable to Ag+
Unresolved: – in vitro: AgNP particle size and coating determine toxicity – In vivo: AgNP particle size and coating not important for distribution
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Acknowledgements
Katlin Daniel Laura Degn Sarah Karafas Keith Houck Jayna Ortenzio Lila Thornton Amy Wang Robert Zucker
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References BACHLER, G., VON GOETZ, N. & HUNGERBUHLER, K. 2013. A physiologically based pharmacokinetic
model for ionic silver and silver nanoparticles. Int J Nanomedicine, 8, 3365-82. COHEN, J. M., TEEGUARDEN, J. G. & DEMOKRITOU, P. 2014. An integrated approach for the in vitro
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