Importance of agglomeration state and exposure conditions for uptake and pro-inflammatory responses to amorphous silica nanoparticles in bronchial epithelial cells

Abstract

Amorphous silica nanoparticles (SiNPs, 30 and 50 nm) and rhodamine-coated SiNPs (50 nm) were examined for their ability to induce pro-inflammatory responses and cytotoxicity in BEAS-2B cells under different experimental conditions. The SiNPs formed micrometre-sized agglomerates in the absence of bovine serum albumin (BSA) in the culture medium, whereas with BSA (0.1%) they were much less agglomerated. All the SiNPs induced IL-6 and IL-8 responses, as measured by ELISA and real-time PCR. The responses were more marked without BSA and higher for the rhodamine SiNPs than the plain ones. Rhodamine SiNPs were not taken up by cells during a 3-h exposure, even though cytokine mRNAs were up-regulated. In conclusion, agglomerated SiNPs induced more potent cytokine responses than the non-agglomerated ones; either due to the agglomeration state per se or more conceivably to a change in surface reactivity against cellular targets due to BSA. Furthermore, cytokine expression was up-regulated independently of SiNP uptake.

Keywords::

• Silica nanoparticles
• agglomeration state
• zeta potential
• inflammation
• uptake

Acknowledgements

We thank E. Lilleaas for expert assistance throughout the study. This work was supported by the Research Council of Norway, through the Environment, Genetics and Health program. MG thanks Prof. U. Fascio of the CIMA centre, University of Milano, for the useful assistance in plain SiNP reflection analysis. The authors would like also to thank Valentina Trevisan (University ‘Ca’ Foscari' Venice) for surface area (BET) measurements.