In vitro delivery and transwell uptake of volatile and semi-volatile organic compounds in an air–liquid interface exposure system

Introduction Volatile organic compounds (VOCs) readily penetrate the respiratory tract and cross the air–liquid interface (ALI), yet their in vitro deposition behavior and dose uniformity remain poorly characterized. Methods In this study, we evaluated the delivered concentration in the basolateral compartment and inter-transwell variability of isopropyl alcohol (IPA), acetone, and benzyl alcohol (BA) in a six-transwell ALI exposure system. VOCs were generated by atomization at airflow rates of 0.2−3 L/min and delivered for 1–2 h. Delivered concentrations were quantified using photoionization detection or UV–Vis spectroscopy, and aerosol characteristics were monitored by scanning mobility particle sizing. Results Despite rapid evaporation and predominantly vapor-phase transport of IPA and acetone, and semi-volatile aerosol BA, VOC delivery to the ALI was reproducible and spatially uniform. IPA and acetone exposures produced coefficients of variation (CVs) below 10% and 16%, respectively, across transwells, whereas benzyl alcohol exhibited higher variability (CV ≤ 19%) due to its lower vapor pressure and higher viscosity. No statistically significant positional differences were observed under any exposure condition. Discussion These findings indicate that volatile organic compounds delivered to the ALI undergo diffusion-driven gas–liquid delivery, resulting in a relatively uniform spatial distribution. This study provides exposure-relevant delivery characterization for VOCs and semi-VOCs in ALI systems, supporting future NAM-based inhalation studies without implying biological dose equivalence.