Role of in vitro exposure to TiO2 nanoparticles in human colorectal carcinoma cells cytotoxicity

Abstract

BACKGROUND AND AIM: TTitanium dioxide nanoparticles (TiO2-NPs) are a revolutionary material that are widely used in in several application fields. However, their large demand has raised many concerns about the risk of TiO2-NPs toxicity in living organisms. Although several studies showed toxic effects of TiO2-NPs on ecosystems, there are few or inconsistence evidences about the possible effects on human health of nanoparticle form (1-100 nm). The biological effect of Titanium dioxide (TiO2) on gastrointestinal tract as a possible adverse effect as been not yet clarify. In particular, the contribution of TiO2-NPs fractions to proliferative effects on tumour cells is debated. In the present study the exposure to three different Titanium chemical forms (ionic Ti, 60 nm TiO2-NPs and TiO2 food additive E171) was explored in human colorectal carcinoma cells (HCT116 and Caco-2). METHODS: Viability was assessed by MTT assay. Western Blot analysis was employed to evaluate the expression of cleaved Caspase-3 and total/cleaved PARP proteins. Colony-forming assays were performed to evaluate the cells proliferation after 7-day culture without Ti chemical forms. RESULTS:The data showed that the exposure to all three forms of Titanium decreased Caco-2 and HCT-116 cell viability in a dose dependent manner compared to untreated control after 72 hours, with a statistically significant effect starting from 1 mg/L for E171 and ionic Ti, and from 10 mg/L for TiO2-NPs. However, western blot analyses showed that the decrease of cells growth was unrelated to apoptosis. Moreover, after removing each Titanium chemical forms, cell proliferation resumed normally CONCLUSIONS:The results of the present study highlight that despite ionic Ti, TiO2-NPs and E171 affect cell viability, all the Ti chemical forms did not induce apoptosis. However, the resuming of cell proliferation after removing the particles support the notion that a better insight of the TiO2-NPs bio-effects is required, to promote a safer use practices of nanomaterials. KEYWORDS: Titanium dioxide, Nanoparticles, Apoptosis, Caco-2 cells, HCT116 cells