Grantee Research Project Results
2021 Progress Report: Measuring Toxicokinetics for Organ-on-Chip Devices
EPA Grant Number: R840031Title: Measuring Toxicokinetics for Organ-on-Chip Devices
Investigators: Hutson, Michael Shane , McCawley, Lisa J. , Markov, Dmitry
Institution: Vanderbilt University
EPA Project Officer: Spatz, Kyle
Project Period: August 1, 2020 through July 30, 2023 (Extended to July 30, 2024)
Project Period Covered by this Report: August 1, 2020 through July 31,2021
Project Amount: $790,352
RFA: Advancing Toxicokinetics for Efficient and Robust Chemical Evaluations (2019) RFA Text | Recipients Lists
Research Category: Chemical Safety for Sustainability
Objective:
As a way to reduce the need for animal testing, EPA and other regulatory agencies have funded investigations of organotypic culture models and organ-on-chip devices. These new approach methodologies place multiple human cell types in appropriate 3D geometries under continuous microfluidic perfusion to better approximate in vivo cellular microenvironments – and thus yield more predictive responses to potential toxicants. Nonetheless, translating organ-on-chip results to predict human health effects still requires in-vitro-to-in-vivo extrapolation. Such extrapolation is always difficult, but becomes even more complicated for organ-on-chip devices because their high surface-to-volume ratios and permeable materials such as PDMS can sequester hydrophobic compounds. Using results from these devices thus requires two calculations: (1) from nominal inlet concentration to in-device cellular dose; and (2) from that dose to equivalent organismal exposure. The latter has been the subject of decades of work, but the former is just beginning to be explored. Our primary objective is to establish methods, measurements and models for the toxicokinetics of PDMS-based organ-on-chip devices.
Progress Summary:
During Year 1 of this grant, we focused on development and validation of experimental protocols for measuring the degree to which a chemical-of-interest partitions from an aqueous solution into PDMS, the rate at which it does so, the rate at which it returns to solution (if at all), and the rate at which it diffuses within PDMS.
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We have developed calibration protocols based on UV/Vis spectroscopy and multi-wavelength Partial Least Squares Regression for non-destructive measurements of the concentration of a chemical remaining in solution. We have used these protocols to assess limit-of-detection for cuvette-based and ATR-crystal-based measurements.
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We have tested disk-soak and channel-soak experiment procedures with fluorescent test chemicals.
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We have fabricated initial versions of two devices for measuring chemical diffusion through PDMS: one based on diffusion from one solution chamber to another through a thin PDMS membrane; a second based on direct time-dependent observation of fluorescent chemical concentration profiles within PDMS via confocal microscopy. We have performed initial tests on these devices and are in the process of refining the experimental design.
In parallel, we have been developing partial-differential equation models to account for time-dependent chemical partitioning and diffusion into PDMS.
Future Activities:
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We will use the experimental protocols developed in Year 1 to measure PDMS interaction parameters and in-PDMS diffusion coefficients for a list of 54 chemicals of interest having a wide range of physico-chemical properties: 48 TSCA Work Plan chemicals that were also screened in ToxCast Phase 1 or 2; three organophosphates being investigated in a blood-brain-barrier-on-a-chip model; and three AhR agonists that are being investigated in an endometrium-on-a-chip model.
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We will investigate how chemical-PDMS interaction parameters are altered by plasma treatment and oxidation of PDMS surfaces.
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We will the use the above results to build a Quantitative Structure-Property Relation (QSPR) model to predict sequestration into PDMS for a wider set of chemicals.
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We will attempt to match our partial-differential-equation models to experimental results and modify the model structure as needed with the goal of developing a predictive model for in-device toxicokinetics.
Supplemental Keywords:
adsorption, risk assessment, bioavailability, dose-response, mammalian, PAH, dioxin, innovative technology, decision making, biology, chemistry, physics, engineering, modeling, analytical, measurement methods, Tennessee, TN, organ-on-a-chip, organotypic cell culture, bioreactors, microfluidicsRelevant Websites:
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.