Abstract
Halloysite nanotubes (HNTs) have been increasingly used in many industrial and biomedical fields. Therefore, the assessment of risk and consequences of exposure to HNTs is very important to better protect human safety. This study aims to investigate the short- (24 or 72 h) and long-term (7 days) cytotoxic effects of HNTs at doses 10–200 µg/mL on human alveolar carcinoma epithelial cells (A549) and human bronchial epithelial cells (BEAS-2B). The effect of HNTs on cell viability, apoptosis, cell proliferation, oxidative/antioxidative status and cell morphology was evaluated. Our results showed that cytotoxicity of HNTs is dependent on dose, cell model and time of exposure. During the time of exposition toxic effects were intensified. To the best of our knowledge, this is the first study to use holo-tomographic microscopy (HTM) to visualise changes in cell morphology due to exposure from HNTs. We observed cells contraction, changes in the size and shape, cell surface folding and cytoplasmic vacuolization, peripheral arrangement of cell nuclei and even increase number of nucleus, which undoubtedly confirmed cytotoxic effect of HNTs at low doses (5 µg/mL and 25 µg/mL). Our results demonstrated that HTM technique provides a new insight into the assessment of HNTs toxicity. Further studies with different cell models are recommended to assess the toxic effect of HNTs on whole human body.
Highlights
Halloysite (Al2Si2O5(OH)4·nH2O) is two-layered aluminosilicate with a unique hollow tubular structure and high aspect ratio
This study evaluates the effect of halloysite nanotubes (HNTs) at doses 10–200 μg/mL on cell viability and apoptosis using human alveolar carcinoma epithelial cells (A549) and human bronchial epithelium cells (BEAS-2B) after short- (24 or 72 h)
The mode values obtained after 24 h, indicated a large share of nanotubes below 100 nm in the F12K medium supplemented with 10% FBS compared with LHC-9 medium
Summary
Halloysite (Al2Si2O5(OH)4·nH2O) is two-layered aluminosilicate with a unique hollow tubular structure and high aspect ratio. HNTs occurs naturally, and it is chemically similar to another clay mineral – kaolin [1, 2]. The characteristics feature, such as unique tubular structure, high aspect ratio, nanoscale lumens, cheap and abundant availability make this nanomaterial useful in many applications [3]. Similarity of HNTs tubular structure to carbon nanotubes (CNTs) may potentially cause the same toxicity such for CNTs, which include pulmonary inflammation and acute phase response following pulmonary exposure and even tumour changes in the human respiratory system [13,14,15,16]. The information on toxicological effects of HNTs on human health is limited [1], there is an emerging need to investigate the potential risk and consequences of effects of exposure to HNTs
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