New 3D in vitro models for assessing the toxicity of carbon nanotubes

Abstract

Introduction. In recent years, there has been interest in 3D cellular models that more accurately reflect in vivo conditions and can become an alternative to animal experiments in assessing the toxicity of nanomaterials. There is a need to develop 3D models of the human respiratory tract that can bridge the gap between traditional in vitro cell cultures and laboratory animals.
 Material and methods. Mono- and co-culture 3D-models based on bronchial epithelial cells BEAS-2B and lung fibroblasts MRC5-SV40 have been developed. Pristine and purified from metal impurities TUBALL™ SWCNTs and Taunit-M MWCNTs were used as materials for the study. The range of concentrations studied included concentrations corresponding to actual occupational exposures (0.0006–100 µg/ml). To assess the cytotoxicity of CNTs in cell models, the level of lactate dehydrogenase (LDH) activity was determined after 72 hours of exposure.
 Results. The cytotoxic effects of CNTs in 2D and 3D cell models manifested themselves in different concentration ranges: a three-dimensional model of bronchial epithelial cells turned out to be more sensitive to the effects of CNTs compared to a monolayer one, while in a spheroid model of fibroblasts a higher cytotoxicity threshold was noted for multi-walled carbon nanotubes compared to traditional cell culture. In three-dimensional cell co-cultures, a significant increase in LDH was observed starting at higher concentrations compared to monocultures.
 Limitations. The present study was limited to the use of one type of cytotoxicity test when examining the effects of CNTs on cells of the respiratory system.
 Conclusion. A method has been developed for three-dimensional cultivation of cells of the human respiratory system to simulate the interaction of epithelial and stromal cells of the lower respiratory tract. Traditional 2D cell models may underestimate or overestimate the toxicity of materials. Improved 3D in vitro models, closer in their properties and morphology to native tissue, are more reliable in determining toxic doses and targets.