An approach to testing undiluted e-cigarette aerosol in vitro using 3D reconstituted human airway epithelium

• Published in: Toxicology in vitro Vol. 54; pp. 391 - 401
• Main Authors: Bishop, E., Haswell, L., Adamson, J., Costigan, S., Thorne, D., Gaca, M.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-02-2019; Elsevier Science Ltd
• Subjects: 3-D technology; 3D lung tissues; Acrolein - analogs & derivatives; Acrolein - toxicity; Aerosols; Air-liquid interface; Beat frequencies; Cell Survival - drug effects; Cigarette smoke; Cigarettes; Cilia; Cilia beat frequency; Cinnamaldehyde; Culture Media - analysis; Cytotoxicity; E-cigarette; Electronic cigarettes; Electronic Nicotine Delivery Systems; Epithelium; Female; Flavor; Flavoring Agents - toxicity; Humans; In vitro; In vitro methods and tests; Lungs; Nasal Mucosa - physiology; Nicotine; Nicotine - analysis; Respiratory tract; Risk assessment; Skin; Smoke; Smoking; Toxicity; Toxicity Tests - methods; Undiluted aerosol; 3D lung tissues; Risk assessment; E-cigarette; Cytotoxicity; Air-liquid interface; In vitro; Undiluted aerosol
• ISSN: 0887-2333; 1879-3177
• DOI: 10.1016/j.tiv.2018.01.010

The data presented here show that to provide an estimate of the relative cytotoxicity and therefore potency of e-cigarettes, undiluted aerosol techniques can be used. With the emergence of electronic nicotine delivery systems, fit-for-purpose in vitro screening methods are required.
Reconstituted 3D human airway epithelium, was exposed to undiluted aerosols at the air-liquid interface, using a Vitrocell VC 10. TEER, cilia beat frequency and cytotoxic responses were assessed. Using two smoking regimes (ISO and HCI) a 3R4F reference cigarette, produced IC50s of 5.2 and 2.1 min, 1458 ng/mL and 1640 ng/mL nicotine respectively. Using an open tank e-cigarette device, a full cytotoxicity dose-response curve was obtained giving an IC50 of 30 min with corresponding nicotine of 10,957 ng/mL, 6–14 times less cytotoxic than cigarette smoke.
A commonly used e-liquid flavourant cinnamaldehyde and known skin sensitizer was added to the standard e-liquid formulation and used as an aerosolised positive control, at 0.1, 0.025, 0.01 and 0%, demonstrating a full dose response.
The delivery of undiluted aerosols in vitro has resulted in increased method sensitivity, throughput and quantitative e-cigarette comparisons. A positive control aerosol generated from a ‘safe’ e-liquid benchmark can inform risk assessments on supportable levels of flavour ingredients.
•Undiluted aerosols were generated using a modified Vitrocell VC10.•Dosimetry analysis showed that the VC10 was unaffected by modifications.•Assay sensitivity increased to allow differences to e-cigarette aerosols to be measured.•Cinnamaldehyde-spiked e-liquids were used as a positive aerosol control.•The use of a ‘safe’ e-liquid as a benchmark for product risk assessment is introduced.