The cytotoxic activity of amorphous silica nanoparticles is mainly influenced by surface area and not by aggregation

• Published in: Toxicology letters Vol. 206; no. 2; pp. 197 - 203
• Main Authors: Rabolli, Virginie, Thomassen, Leen C.J., Uwambayinema, Francine, Martens, Johan A., Lison, Dominique
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 10-10-2011; Elsevier
• Subjects: 3T3 Cells; Adsorption; Agglomeration; Aggregates; Aggregation; Animals; Biological and medical sciences; Cell Line; Cell Survival - drug effects; Culture Media, Serum-Free; Cytochalasin D - pharmacology; Cytotoxicity; Determinants; Endocytosis - drug effects; Fibroblasts - drug effects; Fibroblasts - metabolism; Inhibitory Concentration 50; Macrophages - drug effects; Macrophages - metabolism; Medical sciences; Mice; Microscopy, Electron, Transmission; Nanoparticles; Nanoparticles - chemistry; Nanoparticles - toxicity; Nanoparticles - ultrastructure; Nanostructure; Nephelometry and Turbidimetry; Particle Size; Porosity; Potassium Chloride - chemistry; Silica; Silicon Dioxide - chemistry; Silicon Dioxide - toxicity; Specific surface; Surface Properties; Toxicity; Toxicology; BET; Nanoparticles; Aggregation; DMEM; NP; SNP; ISDD; Cytotoxicity; DLS; ED50; SEM; Silica; Nanoparticle; Ultrafine particle; Surface area; Biological activity; Inorganic compound
• ISSN: 0378-4274; 1879-3169
• DOI: 10.1016/j.toxlet.2011.07.013

► Influence of nanoparticle aggregation on toxicity was investigated with silica-based materials. ► No impact of aggregation on cytotoxicity was found in J774 and 3T3 cell lines. ► Surface area dose determined cytotoxic activity irrespective of aggregation state.
The aggregation state of NP has been a significant source of difficulty for assessing their toxic activity and great efforts have been done to reduce aggregation of and/or to disperse NP in experimental systems. The exact impact of aggregation on toxicity has, however, not been adequately assessed.
Here we compared in vitro the cytotoxic activity of stable monodisperse and aggregated silicon-based nanoparticles (SNP) without introducing a dispersing agent that may affect NP properties.
SNP aggregates (180nm) were produced by controlled electrostatic aggregation through addition of KCl to a Ludox SM sol (25nm) followed by stabilization and extensive dialysis. The size of the preparations was characterized by TEM and DLS; specific surface area and porosity were derived from N2 sorption measurements. Macrophage (J774) and fibroblast (3T3) cell lines were exposed to monodisperse or aggregate-enriched suspensions of SNP in DMEM in absence of serum. The cytotoxic activity of the different preparations was assessed by the WST1 assay after 24h of exposure. Parameters that determined the cytotoxic activity were traced by comparing the doses of the different preparations that induced half a maximal reduction in WST1 activity (ED50) in both cell lines.
We found that ED50 (6–9μg/ml and 15–22μg/ml, in J774 and 3T3, respectively) were hardly affected upon aggregation, which was consistent with the fact that the specific surface area of the SNP, a significant determinant of their cytotoxic activity, was unaffected upon aggregation (283–331m2/g). Thus studying small aggregated NP could be as relevant as studying disperse primary NP, when aggregates keep the characteristics of NP, i.e. a high specific surface area and a nanosize dimension. This conclusion does, however, not necessarily hold true for other toxicity endpoints for which the determinants may be different and possibly modified by the aggregation process.