Transcript Chapter 4 Gastrointestinal ‘luminal’ factors affecting

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Task Group 4 – Charges
The goals of TG4 are to:
• Provide an evaluative overview of the analytical methods that are
or may be useful for detection and characterization of
nanoparticles in these systems, including methods under
development or existing methods for conventional materials that
could be modified to be used for nanoparticles
• Identify conditions and types of particles for which these various
methods are applicable.
• Identify gaps in the methods or methods development needs with
respect to measuring nanoparticles and their transitions in the
alimentary tract.
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Task Group 4 - MEMBERS
David Carlander(COCHAIR)
Tim Duncan (COCHAIR)
Nanotechnology
Industries Association
US Food and Drug
Admin.
James Waldman
Ohio State Univ.
Joseph Hotchkiss
Michigan State Univ., ILSI
North America
Jun Jie Yin
US Food and Drug Admin.
Andrew Whelton
Univ. of South Alabama
Anil Patri
US National Inst. of
Health
Maurizio Avella
Inst. of Chemistry and
Technology of Polymers
(Govt. of Italy)
Chady Stephan
PerkinElmer Company
Paul Westerhoff
Arizona State Univ.
Ruud Peters
RIKILT Inst. of Food Safety
Stefan Weigel
RIKILT, NanoLyse
Vicki Stone
Heriot-Watt Univ.
Christopher Szakal
Dragan Momcilovic
Gregory Noonan
Gurmit Singh
Heather Alger
US National Inst.
Standards & Tech.
US Food and Drug
Admin.
US Food and Drug
Admin.
Health Canada
Scott Thurmond (advisor) US Food and Drug Admin.
Pew Charitable Trusts Jonathan Powell (advisor)
MRC Human Nutrition
Research
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Task Group 4 – White Paper Chapters
1.
Introduction
2.
Overview of detection methods requirements
3.
Detection and characterization of nanomaterial release from
food contact materials
4.
Detection, characterization and quantification of nanomaterials
in foods
5.
Detection and characterization of nanomaterials in the
alimentary tract
6.
Conclusions
This presentation focuses on the main findings from the chapters above
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Chapter 1: Introduction
‘Setting the scene’
• A critical integrative need with respect to understanding
measurement needs will be to combine measurement methods
with alimentary tract modeling approaches and methods.
• Methods will need to incorporate particle detection and
characterization methods in fluid and tissue matrices that extend
to the nanoscale range.
• Many of the methods to detect and measure in this size range are
likely to be new or in development, however, some methods may
be well established but not recognized as “nano-capable”
methods.
• Other methods may need modification to allow them to be useful
for nanomaterial detection and characterization.
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Chapter 2: Overview of detection methods
requirements
• It would not be appropriate to develop experiments to study NPs
in food packaging, food, or the alimentary tract if the
characteristics of the starting NPs are insufficient.
• Sizing of starting NPs should be accomplished with more than one
method (if possible, three methods among TEM, AFM, DLS, and
FFF)
• Outside of sizing information, phase information can be attained
with diffraction-based STEM
• Confirmatory elemental information can be obtained with one of
the hyphenated ICP techniques (e.g.ICP-MS)
• However, both organic and inorganic pristine NP characterization
is not well standardized/validated and may in and of itself be one
of the areas of largest benefit from continued study
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Chapter 2: Overview of detection methods
requirements
Confidence in the preliminary material measurements is a requirement
before measurement attempts in more complex matrices can be trusted
analytically
Comparisons can then:
1)
relate to the original starting materials,
2)
answer questions of whether commercial test materials are relevant
to those used in foods/food packaging,
3)
identify predictive behavior of the NPs in foods based on
characteristics such as water-based or fat-based,
4)
provide predictive properties of the NPs both after industrial
processing and in food-based and alimentary tract-based
temperatures and viscosities,
5)
distinguish the consistency amongst the NP starting materials for
large batches, and
6)
differentiate natural NMs vs. deliberately added NMs.
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Chapter 2: Overview of detection methods
requirements
Assuming that the NPs are well-characterized, a brief overview of
current NP and/or NM-based characterization methods are
presented as they may relate to food-based, food packaging-based,
and alimentary tract-based complex matrices:
•
Compositional analysis: ‘how much is there?’ and ‘is it there at all’
ICP-MS, SP-ICP-MS, AAS, SPR, HPLC, FFF, UV-vis, surface-based techniques for
aggregates. MOSTLY developed for inorganic NPs/NMs; organic relatively limited
and needed
•
Imaging analysis: ‘where is it?’
TEM, SEM-EDS, CARS, CLSM, some MS for aggregates
•
Emerging methods: ‘what can we answer later that we cannot answer
now?’
Microchannel resonators coupled with others above, SIMS/XPS, APT, DART, LTP,
DESI, LMJ-SSP
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Large amount of work
exhibited; methods with
best chance for success
or standardization
Some limited examples
exhibited; methods in
need of immediate
investigation
Unknown ability for
detection; lack of
available methods for
detection
Isolated examples
exhibited; methods of
promise for future study
and development
Is NP or NM
organic or
inorganic?
Organic
Inorganic
Expected to
Expected to
dissolve/digest
HPLC, FFF,
Imaging
Uv-vis, CLSM,
Specific ELISA
Total Quant
Most
documented:
ICP-MS
If individual
NPs: CLSM, TIRF
If aggregated:
(if fluorescent)
SIMS, LEIS, AFM
CARS, XPS,
Expected to
Expected to
dissolve/digest
stay as NP/NM
stay as NP/NM
Others:
Imaging
AAS, SPR, HPLC,
FFF
ICP-MS?
Sizing or
Aggregation:
Total quant
ICP-MS and
Chemical ID
SP-ICP-MS
TEM
Decision Tree for Choosing Measurement Methods for the Oral
Uptake of Engineered Nanomaterials
*Note: this decision tree is based on nanoparticle and nanomaterial analysis either in the pristine state
or within simplified matrices and does not take into account differences due to nanomaterial extraction
from the surrounding matrix nor the effects of the matrix on ultimate detection limits. Because of the
complexities of food, food packaging, and the alimentary tract as an analytical matrix, the resulting
utility of the decision tree may need to be augmented. Rather than this being a comprehensive
representation of nanomaterial characterization, an emphasis was placed on what methods can yield
near-term accomplishments as well as where considerable amounts of additional research are needed.
If individual
NPs: SEM-EDS,
TEM-EELS, etc.
If aggregated:
SIMS
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Chapter 2: Overview of detection methods
requirements
• An area of community need is in the validation of the pristine NP and NM
methods in terms of uncertainties, limits of detection, and potential
measurement flaws – if the characterization is not quantifiable with
appropriately known error ranges, it will be near impossible to make any
quantitative claims for detected NPs and NMs in the more complex
matrices.
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Chapter 3: Detection and characterization of
nanomaterial release from food contact materials
• Food contact materials include: food packaging, restaurant
takeout and retail food storage containers, surfaces of food
preparation (utensils, cutting boards, etc) and food processing
(conveyors, nozzles, etc.) equipment, appliance linings, potable
water infrastructure
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The Four “D” Nanomaterial Release Pathways
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Chapter 3: Detection and characterization of
nanomaterial release from food contact materials
• Inorganic ENMs have been the most heavily scrutinized materials
and nanosilver products have received the greatest attention.
• The dissolution of ENMs embedded within nanocomposites has
not been directly studied, but some literature data imply
dissolution is significant.
• No studies were found that reported ENM diffusion through nonfood materials into water.
• It should be noted that NP environmental release data remains
very limited and there is disagreement over whether existing
methods to assess small molecule migration are adequate for
measuring migration of nanoparticles. This deficiency hinders our
ability to comprehensively assess and manage the risk associated
with nanoscale materials in drinking water and food packaging
areas.
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Chapter 3: Detection and characterization of
nanomaterial release from food contact materials
• Theoretical modeling of ENP diffusion
• Methods to assess migration
Challenges
• Assessment of post-release particle morphology and
transformation processes
• Are conventional food simulants appropriate to assess quantity
and form of migrated nanoparticles?
• E.g., can food simulants simulate quantity of migrated ENP, and also postmigration processes like agglomeration, dissolution, O-ripening etc.
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Chapter 4: Detection, characterization and
quantification of nanomaterials in foods
• Overview of flow path towards characterization and detection of
nanomaterials in food
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Chapter 4: Detection, characterization and
quantification of nanomaterials in foods
• Most analytical techniques require sample preparation prior to
injection/insertion into high-end instrumentation to quantify
nanomaterials.
Examples of sample preparation methods
1.
Digestion of food matrices liberate ENMs (e.g. acids, alkalis,
enzymatic, peroxide)
2.
Separation of ENMs from liquids by ultrafiltration or
centrifugation
3.
Solvent extraction (e.g., non-polar organics, cloud point
extraction, ionic liquids)
4. Solid phase extraction
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Chapter 5: Detection and characterization of
nanomaterials in the alimentary tract
• Nanomaterials in the gut may be of exogenous and endogenous
origin
• There are situations when it is unclear on whether nanomaterial
gets absorbed as particles or (and also) as ions
• Prevailing conditions within various compartments of the
alimentary tract may exert a wide spectrum of effects on passing
nanoparticles
• There may be low rates of nanoparticulate matter absorption in
the alimentary tract
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Chapter 5: Detection and characterization of
nanomaterials in the alimentary tract
Existing analytical methods for detection
• in vitro gastrointestinal system. Simulate human stomach and
small intestine.
• Dynamic light scatter
• Surface Plasmon Resonance (SPR)
• Caco-2 monolayer assay
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Chapter 5: Detection and characterization of
nanomaterials in the alimentary tract
Methods under development for detection
• Enzyme linked immunosorbency assay (ELISA) screening kits
Existing methods that could be modified to be used for detecting
nanoparticles in the alimentary canal
• In vivo: Ingestion studies, tail vein blood collection, everted gut
sac, fecal excretion, lymph duct cannulation
• In vitro: Artificial gastrointestinal system, intestinal epithelial
monolayer assay
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Chapter 5: Detection and characterization of
nanomaterials in the alimentary tract
Methods for characterization of nanoparticles in the alimentary
tract
Existing analytical methods for characterization
Techniques have benefits and limitations (e.g., specificity, resolution,
sample preparation)
•
Electron microscopy (EM)
•
Transmission Electron Microscopy (TEM)
•
Scanning Electron Microscopy (SEM)
•
Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
•
Matrix-Assisted Laser Desorption/Ionization – Time of Flight (MALDITOF) Mass spectroscopy
•
Coherent anti-Stokes Raman scattering (CARS) microscopy
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Chapter 6: White Paper Conclusions
• There is no single definitive method for characterization of
nanoparticles in the alimentary tract
• Analyses should not depend on only one method; instead, several
complementary methods should, if possible, be used.
• Coupled techniques should be further developed and increasingly
applied
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On behalf of TG4
Thank you for your attention!
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