In vitro dosing

Possible dosing set-ups

The most reliable dosing set-up can depend on the assay requirements (e.g., oxygenation, high-throughput, metabolic capacity of tissues, etc.) and the physicochemical properties (i.e., potency, volatility, lipophilicity, plasma protein binding, aqueous and biological half-lives).

Four main set-ups are proposed:
Standard dosing

Standard dosing of exposure medium with chemical in organic solvent in microtiter plates seeded with cells.
Closed glass vials

Dosing of exposure medium with chemical in organic solvent in closed glass 1.7 mL autosampler vials seeded with cells.
Partition-controlled dosing

Dosing of exposure medium with chemical in polymer discs in 24-well plates with cells in inserts.
Closed chamber

Dosing in closed chamber systems.

Decision tree

In the first phase of the Better in vitro Dosing project, a decision tree was developed to select the best dosing set-up depending on the physicochemical properties of the chemical. The decision tree can be downloaded here.

The future aim in this project is to define cut-off criteria in the decision tree for use in OECD guidelines for in vitro testing of difficult-to-control chemicals.
Decision tree
Note: Decision-tree for toxicologists to determine, based on the properties of chemical (i.e., volatility, lipophilicity, stability in medium and plasma protein binding affinity) and in vitro assay properties (e.g., amenability to closed systems, possibility to seed and perform readouts in autosampler vials), which dosing method to employ in in vitro toxicity assay and what sorption processes to account for using in vitro distribution modelling.