Assessment of Human Lung Macrophages After Exposure to Multi-Walled Carbon Nanotubes Part I. Cytotoxicity

Due to the widespread production and use of carbon nanotubes in almost every area of science (i.e., drug delivery, biosensors, fuel cells and thermal management systems), they are receiving considerable attention for their novel mechanical, electrical and chemical properties. At this time of high exposure potential, it is critical to ascertain the biological impact of these materials on likely target organs, tissues and cells, such as those of the lung. The aim of this study was to evaluate the degree of cytotoxicity to human lung macrophage (U937) cells after exposure to unpurified or acid-purified multi-walled carbon nanotubes. Cells were incubated with multi-walled carbon nanotubes and assessed for cytotoxicity, generation of reactive oxygen species, morphological changes and uptake. The results demonstrate that multi-walled carbon nanotubes can accumulate in human lung macrophage cells to different degrees based on their surface chemistry. MWNT-COOH reduces cell viability in a dose-dependent manner under these experimental conditions (5–50 g/ml, 2–24 h). However, images of individual cells demonstrate morphological changes at low concentrations. Therefore, before nanomaterials are fully accepted and integrated into biological systems, they will continue to undergo further scrutiny at various stages of their processing (i.e., before and after purification) and with models ranging from simple to complex (i.e., cells vs. whole animals) to gain a better understanding between their physicochemical properties and bio-effects.