Upload
naeva
View
32
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Task Group 4 Measurement Methods Measurement Methods for the Oral Uptake of Engineered Nanomaterials from Human Dietary Sources April 16, 2013 Webinar NanoRelease Food Additive. 1. www.riskscience.org. Task Group 4 – Charges. The goals of TG4 are to: - PowerPoint PPT Presentation
Citation preview
Task Group 4 Measurement Methods
Measurement Methods for the Oral Uptake of Engineered Nanomaterials
from Human Dietary Sources
April 16, 2013 WebinarNanoRelease Food Additive
1www.riskscience.org
TG4 - Measurement Methods
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.
Task Group 4 – Charges
2www.riskscience.org
Task Group 4 - MEMBERSDavid Carlander(COCHAIR) Nanotechnology
Industries Association James Waldman Ohio State Univ.
Tim Duncan (COCHAIR) US Food and Drug Admin. Joseph Hotchkiss Michigan State Univ., ILSI
North America
Andrew Whelton Univ. of South Alabama Jun Jie Yin US Food and Drug Admin.
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.
Christopher Szakal US National Inst. Standards & Tech. Ruud Peters RIKILT Inst. of Food Safety
Dragan Momcilovic US Food and Drug Admin. Stefan Weigel RIKILT, NanoLyse
Gregory Noonan US Food and Drug Admin. Vicki Stone Heriot-Watt Univ.
Gurmit Singh Health Canada Scott Thurmond (advisor) US Food and Drug Admin.
Heather Alger Pew Charitable Trusts Jonathan Powell (advisor) MRC Human Nutrition Research
3www.riskscience.org
TG4 - Measurement Methods
1. Introduction2. Overview of detection methods requirements3. Detection and characterization of nanomaterial release from
food contact materials4. Detection, characterization and quantification of
nanomaterials in foods5. Detection and characterization of nanomaterials in the
alimentary tract 6. Conclusions
This presentation focuses on the main findings from the chapters above
Task Group 4 – White Paper Chapters
4www.riskscience.org
TG4 - Measurement Methods
‘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.
Chapter 1: Introduction
5www.riskscience.org
TG4 - Measurement Methods
• 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
Chapter 2: Overview of detection methods requirements
6www.riskscience.org
TG4 - Measurement Methods
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.
Chapter 2: Overview of detection methods requirements
7www.riskscience.org
TG4 - Measurement Methods
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
Chapter 2: Overview of detection methods requirements
8www.riskscience.org
Is NP or NM organic or inorganic?
Organic
Expected to dissolve/digest
HPLC, FFF, Uv-vis, CLSM, Specific ELISA
Expected to stay as NP/NM
Imaging
If individual NPs: CLSM, TIRF(if fluorescent)
If aggregated:CARS, XPS, SIMS, LEIS,
AFM
Total Quant
ICP-MS?
Inorganic
Expected to dissolve/digest
Most documented:
ICP-MS
Others:AAS, SPR, HPLC,
FFF
Expected to stay as NP/NM
Imaging
Sizing or Aggregation:
TEMChemical ID
If individual NPs: SEM-EDS, TEM-EELS, etc.
If aggregated:SIMS
Total quant
ICP-MS andSP-ICP-MS
Large amount of work exhibited; methods with best chance for success or standardization
Some limited examples exhibited; methods in need of immediate investigation
Isolated examples exhibited; methods of promise for future study and development
Unknown ability for detection; lack of available methods for detection
*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.
Decision Tree for Choosing Measurement Methods for the Oral Uptake of Engineered Nanomaterials
9www.riskscience.org
TG4 - Measurement Methods
• 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.
Chapter 2: Overview of detection methods requirements
10www.riskscience.org
TG4 - Measurement Methods
• 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
Chapter 3: Detection and characterization of nanomaterial release from food contact materials
11www.riskscience.org
TG4 - Measurement Methods
The Four “D” Nanomaterial Release Pathways
12www.riskscience.org
TG4 - Measurement Methods
• 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 non-food 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.
Chapter 3: Detection and characterization of nanomaterial release from food contact materials
13www.riskscience.org
TG4 - Measurement Methods
• 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 post-migration processes like agglomeration, dissolution, O-ripening etc.
Chapter 3: Detection and characterization of nanomaterial release from food contact materials
14www.riskscience.org
TG4 - Measurement Methods
• Overview of flow path towards characterization and detection of nanomaterials in food
Chapter 4: Detection, characterization and quantification of nanomaterials in foods
15www.riskscience.org
TG4 - Measurement Methods
• Most analytical techniques require sample preparation prior to injection/insertion into high-end instrumentation to quantify nanomaterials.
Examples of sample preparation methods1. Digestion of food matrices liberate ENMs (e.g. acids,
alkalis, enzymatic, peroxide)2. Separation of ENMs from liquids by ultrafiltration or
centrifugation3. Solvent extraction (e.g., non-polar organics, cloud
point extraction, ionic liquids)4. Solid phase extraction
Chapter 4: Detection, characterization and quantification of nanomaterials in foods
16www.riskscience.org
TG4 - Measurement Methods
• 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
Chapter 5: Detection and characterization of nanomaterials in the alimentary tract
17www.riskscience.org
TG4 - Measurement Methods
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
Chapter 5: Detection and characterization of nanomaterials in the alimentary tract
18www.riskscience.org
TG4 - Measurement Methods
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
Chapter 5: Detection and characterization of nanomaterials in the alimentary tract
19www.riskscience.org
TG4 - Measurement Methods
Methods for characterization of nanoparticles in the alimentary tractExisting analytical methods for characterizationTechniques 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
(MALDI-TOF) Mass spectroscopy• Coherent anti-Stokes Raman scattering (CARS) microscopy
Chapter 5: Detection and characterization of nanomaterials in the alimentary tract
20www.riskscience.org
TG4 - Measurement Methods
• 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
Chapter 6: White Paper Conclusions
21www.riskscience.org
TG4 - Measurement Methods
On behalf of TG4
Thank you for your attention!
22www.riskscience.org