The Control of Hydrophobic Compound Exposure in In Vitro Tests for Genotoxicity

Abstract

Several of the OECD recommended tests for genotoxicity are in vitro tests, involving the use of open plastic vessels and culture plates, rich culture media, or metabolic activation. These result in volatile, sorptive, and biotransformation losses of the test compound, and thus to poorly defined exposure. This has implications for the apparent sensitivity of the assay as well as for establishing a reliable relationship between concentration and response. These issues are particularly relevant for hydrophobic organic compounds (HOCs) which are difficult to initially dissolve in aqueous media and particularly susceptible to sorptive losses. Therefore, the in vitro genotoxicity testing of HOCs requires techniques that compensate for losses and lead to defined and constant dissolved exposure concentrations. Here, passive dosing can play a useful role. Passive dosing involves a dominating reservoir of polymer-sorbed HOC acting as a partitioning source to the test medium, maintaining defined and constant dissolved concentrations. This chapter introduces passive dosing for the control of HOC dissolved concentrations during in vitro genotoxicity tests, covering considerations for selecting a suitable passive dosing polymer and its dimensioning, as well as procedures for cleaning and loading the dosing polymer with the test HOC(s).