An interlaboratory in vitro aerosol exposure system reference study

Abstract

Given the complexity of inhaled substances, the aerosol exposure environment has seen diversification and development of setups in conjunction with the evolving in vitro toxicology space. Each laboratory uses its in vitro exposure system differently (different protocols, adaptations, and biological analysis). Unfortunately, as systems diversify, so does the complexity of comparing multiple systems in a “standardized” manner. As yet, no one has compared simply whether these diverse systems can all generate a consistent aerosol stream, which is paramount prior to transit and exposure. This study has compared, at source, aerosol generation (using nicotine as an exposure marker) in nine in vitro whole-aerosol exposure setups (seven different systems) across five distinct geographically independent locations, including the UK, the USA, Switzerland, Germany, and Japan. The results demonstrate that, despite system-wide differences (adaptations, nuances, and application), these systems—when appropriately maintained and used under a prescribed set of established conditions can all generate a consistent and statistically comparable aerosol stream. These data will be invaluable for new researchers and established laboratories, so they may benchmark against this study. Finally, this interlaboratory comparison combined with the wealth of transit and exposure interface data, may help the environment move towards a truly validated and consistent approach to aerosol exposure. Such an approach could be replicated for other aerosolized products, such as e-cigarettes and heated tobacco products.

Characterisation of a smoke/ aerosol exposure in vitro system (SAEIVS) for delivery of complex mixtures directly to cells at the air‐liquid interface

“…However, this is currently the only machine of this type; therefore, standardisation across multiple different systems is important to ensure that outcomes can be compared both within and between laboratories. For example, characterisation of systems using a reference product and aligned dosimetry measures have been used for this purpose (Miller‐Holt et al, 2022; Thorne, Adamson, et al, 2021). There are working groups who carry out such studies, for example, those of the Institute of In Vitro Sciences (Miller‐Holt et al, 2022).…”

“…The SAEIVS is one of many in vitro smoke/ aerosol exposure systems (Thorne & Adamson, 2013; Thorne, Adamson, et al, 2021). The experimentation carried out using any such system should therefore be subject to a level of standardisation to ensure reproducible results.…”

“…for this purpose (Miller-Holt et al, 2022;Thorne, Adamson, et al, 2021). There are working groups who carry out such studies, for example, those of the Institute of In Vitro Sciences (Miller-Holt et al, 2022).…”

“…Smoke is then delivered to cells situated within an exposure module (Adamson et al, 2016; Behrsing et al, 2018). There are a number of such systems and set‐ups available; these have recently been evaluated by Thorne, Adamson, et al (2021). Many exposure systems have the functions to dilute the whole smoke/ aerosols generated (with air) to operator‐defined puffing regimes, and to smoke multiple products at the same time, to support specific study designs and dose–response testing.…”

Considerations on dosimetry for in vitro assessment of e-cigarette toxicity

“…However, this easy handling system remains to be characterized in a complete setup dedicated for e-cigarettes aerosol exposure using an appropriate puffing regimen. Besides Vitrocell and Borgwaldt, several manufacturers have developed others smoking machine/exposure chamber (Burghardt, CULTEX, Philip Morris, British American Tobacco…) with various engineering processes and technologies [ 46 ]. Taken together, the heterogeneity of both exposure protocols and exposure systems strengthens the difficulty of comparing data obtained from e-cigarette toxicological studies and to draw robust conclusions concerning e-cigarette health effects.…”