Bashir Mustafa Mohamed, Navin Kumar Verma, Adriele Prina-Mello, Yvonne Williams, Anthony M Davies, Gabor Bakos, Laragh Tormey, Connla Edwards, John Hanrahan, Anna Salvati, Iseult Lynch, Kenneth Dawson, Dermot Kelleher, and Yuri Volkov, Activation of stress-related signalling pathway in human cells upon SiO2 nanoparticles exposure as an early indicator of cytotoxicity, Journal of Nanobiotechnology, 9, 29, 2011
Journal of Nanobiotechnology; 9; 29;
Background: Nanomaterials such as SiO2 nanoparticles (SiO2NP) are finding increasing
applications in the biomedical and biotechnological fields such as disease diagnostics, imaging,
drug delivery, food, cosmetics and biosensors development. Thus, a mechanistic and systematic
evaluation of the potential biological and toxic effects of SiO2NP becomes crucial in order to assess
their complete safe applicability limits.
Results: In this study, human monocytic leukemia cell line THP-1 and human alveolar epithelial
cell line A549 were exposed to a range of amorphous SiO2NP of various sizes and concentrations
(0.01, 0.1 and 0.5 mg/ml). Key biological indicators of cellular functions including cell population
density, cellular morphology, membrane permeability, lysosomal mass/pH and activation of
transcription factor-2 (ATF-2) were evaluated utilizing quantitative high content screening (HCS)
approach and biochemical techniques. Despite the use of extremely high nanoparticle
concentrations, our findings showed a low degree of cytotoxicity within the panel of SiO2NP
investigated. However, at these concentrations, we observed the onset of stress-related cellular
response induced by SiO2NP. Interestingly, cells exposed to alumina-coated SiO2NP showed low
level, and in some cases complete absence, of stress response and this was consistent up to the
highest dose of 0.5 mg/ml.
Conclusions: The present study demonstrates and highlights the importance of subtle biological
changes downstream of primary membrane and endocytosis-associated phenomena resulting from
high dose SiO2NP exposure. Increased activation of transcription factors, such as ATF-2, was
quantitatively assessed as a function of i) human cell line specific stress-response, ii) SiO2NP size
and iii) concentration. Despite the low level of cytotoxicity detected for the amorphous SiO2NP
investigated, these findings prompt an in-depth focus for future SiO2NP-cell/tissue investigations
based on the combined analysis of more subtle signalling pathways associated with accumulation
mechanisms, which is essential for establishing the bio-safety of existing and new nanomaterials.
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