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

In vitro testing is important to characterise biological effects of consumer products, including nicotine delivery products such as cigarettes, e-cigarettes and heated tobacco products. Users' cells are exposed to these products' aerosols, of variant chemical compositions, as they move along the respiratory tract. In vitro exposure systems are available to model such exposures, including delivery of whole aerosols to cells, and at the air-liquid interface. Whilst there are clear advantages of such systems, factors including time to aerosol delivery, aerosol losses and number of cell cultures that can be exposed at one time could be improved. This study aimed to characterise a custom-built smoke/ aerosol exposure in vitro system (SAEIVS) using 1R6F reference cigarette smoke. This system contains five parallel smoking chambers and delivers different dilutions of smoke/ aerosol to two separate cell culture exposure chambers in <10 s. Using two dosimetry measures (optical density 400 nm [OD 400 ]; mass spectrometric nicotine quantification), the SAEIVS demonstrated excellent linearity of smoke dilution prior to exposure (R 2  = 0.9951 for mass spectrometric quantification; R 2  = 0.9965 for OD 400 ) and consistent puff-wise exposures across 24 and 96 well plates in cell culture relevant formats (e.g., within inserts). Smoke loss was lower than previously reported for other systems (OD 400 : 16%; nicotine measurement: 20%). There was good correlation of OD 400 and nicotine measurements, indicating that OD was a useful surrogate for exposure dosimetry for the product tested. The findings demonstrated that the SAEIVS is a fit-for-purpose exposure system for the reproducible dose-wise exposure assessment of nicotine delivery product aerosols.