Grantee Research Project Results
2024 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 May 6, 2025
Project Period Covered by this Report: August 1, 2023 through July 31,2024
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-onchip 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 indevice 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:
Through Year 4 of this grant, we have completed experiments on a priority list of chemicals currently in use in other organ-on-a-chip toxicology studies. These include three organophosphate pesticides (paraoxon, parathion and chlorpyrifos), and two AhR agonists (benzo[a]pyrene and indole). We have also completed experiments on a longer and more widely varying list of 40 chemicals. We have measured the degree to which each chemical-ofinterest partitions from an aqueous solution into PDMS, the rate at which it does so, the rate at which it returns to solution, and the rate at which it diffuses across a thin (80-µm) PDMS membrane. We have also completed experiments that investigated several strategies for reducing chemical-PDMS interactions.
1. We have developed calibration protocols based on UV/Vis spectroscopy and multiwavelength 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.
2. We have conducted disk-soak and diffusion-through-membrane experiments, and we have developed nonlinear regression methods for simultaneously fitting these experimental results to models that return well-constrained estimates of the relevant parameters: PDMS-to-water partition coefficient, K; and diffusion constant in PDMS, Dp.
3. We have validated methods for conducting disk-soak and diffusion-through-membrane experiments for chemicals with limited water solubility. Experiments can be done in 30 to 70% water-DMSO mixtures and the results extrapolated to pure aqueous solution using a log-linear relationship for the PDMS-to-water partition coefficient, K.
4. We have used disk-soak experiments for indole, which has high affinity for and high diffusion through PDMS, to test how PDMS interaction parameters vary among PDMS lots and how they are altered by annealing PDMS.
5. We have used disk-soak and diffusion-through-membrane experiments to evaluate several mitigation strategies for reducing chemical sequestration by PDMS.
a. We found that replacing PDMS with an alternative SEBS co-polymer does not reduce partitioning of hydrophobic compounds into the polymer, but it does strongly reduce diffusion of these compounds deeper into the polymer bulk.
b. We found that addition of 5-10% (w/v) of bovine serum albumin to an aqueous solution can strongly reduce partitioning of hydrophobic chemicals into PDMS.
6. We have conducted experiments in which fluorescent dyes were observed via confocal microscopy as they diffuse out of a solution-filled channel and into a surrounding block of PDMS. We validated that the diffusion constants estimated from these experiments match those from our disk-soak and diffusion-through-membrane experiments.
7. We have used the above experimental protocols and simultaneous regression techniques to complete measurements of PDMS interaction parameters and in-PDMS diffusion coefficients for 40 additional chemicals of interest. This set of chemicals covers a wide range of physico-chemical properties.
8. We have developed partial-differential-equation models of partitioning into PDMS and diffusion through PDMS to predict chemical distribution within the user-defined geometry of specific microfluidic devices at different flow rates. We confirmed that these models can accurately predict chemical loss under continuous flow through a microfluidic channel in PDMS.
Future Activities:
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.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 5 publications | 1 publications in selected types | All 1 journal articles |
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Hermann NG, Ficek RA, Markov DA, McCawley LJ, Hutson MS. Toxicokinetics for organ-on-chip devices. Lab on a Chip [Epub ahead of print] doi:10.1101/2024.10.10.617253. |
R840031 (2024) |
not available |
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:
Vanderbilt-Pittsburgh Resource For Organotypic Models for Predictive Toxicology Exit
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.