Moving into advanced nanomaterials. Toxicity of rutile TiO2 nanoparticles immobilized in nanokaolin nanocomposites on HepG2 cell line

Abstract

Immobilization of nanoparticles on inorganic supports has been recently developed, resulting in the creation of nanocomposites. Concerning titanium dioxide nanoparticles (TiO NPs), these have already been developed in conjugation with clays, but so far there are no available toxicological studies on these nanocomposites. The present work intended to evaluate the hepatic toxicity of nanocomposites (C-TiO), constituted by rutile TiO NPs immobilized in nanokaolin (NK) clay, and its individual components. These nanomaterials were analysed by means of FE-SEM and DLS analysis for physicochemical characterization. HepG2 cells were exposed to rutile TiO NPs, NK clay and C-TiO nanocomposite, in the presence and absence of serum for different exposure periods. Possible interferences with the methodological procedures were determined for MTT, neutral red uptake, alamar blue (AB), LDH, and comet assays, for all studied nanomaterials. Results showed that MTT, AB and alkaline comet assay were suitable for toxicity analysis of the present materials after slight modifications to the protocol. Significant decreases in cell viability were observed after exposure to all studied nanomaterials. Furthermore, an increase in HepG2 DNA damage was observed after shorter periods of exposure in the absence of serum proteins and longer periods of exposure in their presence. Although the immobilization of nanoparticles in micron-sized supports could, in theory, decrease the toxicity of single nanoparticles, the selection of a suitable support is essential. The present results suggest that NK clay is not the appropriate substrate to decrease TiO NPs toxicity. Therefore, for future studies, it is critical to select a more appropriate substrate for the immobilization of TiO NPs.

Genotoxicity of TiO2 Nanoparticles in Four Different Human Cell Lines (A549, HEPG2, A172 and SH-SY5Y)

“…Furthermore, premutagenic lesions, as the ones detected by the comet assay, may be removed by an efficient DNA repair system before their conversion to mutations or chromosome breaks (i.e., the lesions detected in the MN test). In agreement, Bessa et al [62] and El Yamani et al [63] observed that DNA damage induced by TiO 2 NPs on A549 and HepG2 cells decreased from 3 to 24 h, indicating a potential induction of DNA repair pathways after the first few hours of exposure.…”

The size‐dependent apoptotic effect of titanium dioxide nanoparticles on endothelial cells by the intracellular pathway

“…29 It is now known that the intracellular approach of apoptosis is mainly initiated by the induction of p53 as a response to DNA damage induced by genotoxic agents. 29 A number of studies have shown that nano-TiO 2 can induce DNA damage and adversely affect both major DNA repair mechanisms: base excision repair and nucleotide excision repair, showing a genotoxic potential to human cells 10,31,[42][43][44][45] and animal models. 24,46,47 We also found that the four sizes of nano-TiO 2 could induce significant DNA damages and micronuclei in human BEAS-2B cells (unpublished data).…”

Investigation of the in vitro genotoxicity of two rutile TiO2 nanomaterials in human intestinal and hepatic cells and evaluation of their interference with toxicity assays

“…Additionally, numerous publications have demonstrated the interference of TiO 2 NMs in a wide range of biological assays, which may then lead to false-positive or false-negative results (Azqueta et al 2015, Di Bucchianico et al 2016, Ferraro et al 2016, Bessa et al 2017, Li et al 2017). In the current study, we have therefore described and taken into account various sources of interference within our assays.…”