Cultex Laboratories develops strategy for e-cigarette testing
Cultex Laboratories develops strategy for e-cigarette testing using normal bronchial epithelial cells
The number of sold e-cigarettes raised rapidly since the introduction of the product in 2003. The annual sales in the UK for example increased about 25% from 2013 to 2014 and in the United States even about 40%. E-cigarettes are often advertised to be safer than regular cigarettes, but scientific evidence is meagre. Some chemical studies analyzed the components of e-liquids, but these investigations do not give information about the effects of e-cigarette vapor in the human lung, the primary target organ, which is characterized by an organ specific morphology and physiology. In clinical studies, e-cigarette consumers have been examined after short-term usage of e-cigarettes, but possible long-term effects are still unknown. A variety of in vitro studies have been carried out with different cells except those of the target organ. Furthermore, liquids or liquid extracts were added to the cell cultures, but freshly generated e-liquid vapor was not analyzed.
Cultex Laboratories GmbH developed a test strategy to analyze the effects of native e-cigarette vapor after direct exposure of human cells derived from the lung (primary normal human bronchial epithelial cells, NHBE). The cells are cultivated at the air-liquid interface to realize a direct contact between the surrounding atmosphere and the cell layer. The exposure is carried out in the CULTEX® RFS compact, allowing the parallel exposure of six cell culture samples.
Comparing the effects of cigarette mainstream smoke and e-liquid vapor on the cell viability, regular cigarettes show a toxicity, which is about 5.5 time higher (normalized to the number of puffs taken). However, also e-cigarette vapor induced cytotoxic effects, the cell viability is only about 65% of clean air exposed cells, pointing to a cytotoxic potency of the liquid components.
The exposure experiments were repeated with three different cell donors and showed each comparable and reproducible results, confirming the stability of the test method as well as the reproducibility of the data.
Figure: Effects of e-cigarette vapor and mainstream smoke exposure on the cell viability of normal human bronchial epithelial cells
In the future, the testing of e-cigarette liquids is becoming more and more important to guarantee quality and safety for the consumer. Here, in vitro tests based on primary normal human bronchial epithelial cells deliver relevant data about toxic components and should therefore be part of the routine testing procedures of e-liquid manufacturers.