BackgroundEngineered nanomaterials display unique properties that may have impact on human health, and thus require a reliable evaluation of their potential toxicity. Here, we performed a standardized in vitro screening of 23 engineered nanomaterials. We thoroughly characterized the physicochemical properties of the nanomaterials and adapted three classical in vitro toxicity assays to eliminate nanomaterial interference. Nanomaterial toxicity was assessed in ten representative cell lines.ResultsSix nanomaterials induced oxidative cell stress while only a single nanomaterial reduced cellular metabolic activity and none of the particles affected cell viability. Results from heterogeneous and chemically identical particles suggested that surface chemistry, surface coating and chemical composition are likely determinants of nanomaterial toxicity. Individual cell lines differed significantly in their response, dependent on the particle type and the toxicity endpoint measured.ConclusionIn vitro toxicity of the analyzed engineered nanomaterials cannot be attributed to a defined physicochemical property. Therefore, the accurate identification of nanomaterial cytotoxicity requires a matrix based on a set of sensitive cell lines and in vitro assays measuring different cytotoxicity endpoints.

BackgroundMany toxicological studies on silica nanoparticles (NPs) have been reported, however, the literature often shows various conclusions concerning the same material. This is mainly due to a lack of sufficient NPs characterization as synthesized as well as in operando. Many characteristics of NPs may be affected by the chemistry of their surroundings and the presence of inorganic and biological moieties. Consequently, understanding the behavior of NPs at the time of toxicological assay may play a crucial role in the interpretation of its results.The present study examines changes in properties of differently functionalized fluorescent 50 nm silica NPs in a variety of environments and assesses their ability to absorb proteins from cell culture medium containing either bovine or human serum.MethodsThe colloidal stability depending on surface functionalization of NPs, their concentration and time of exposure was investigated in water, standard biological buffers, and cell culture media by dynamic light scattering (DLS), zeta potential measurements and transmission electron microscopy (TEM). Interactions of the particles with biological media were investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) in bovine and human serum, and extracted proteins were assessed using matrix-assisted laser desorption/ionization-time of flight technique (MALDI-TOF).ResultsIt was recognized that all of the studied silica NPs tended to agglomerate after relatively short time in buffers and biological media. The agglomeration depended not only on the NPs functionalization but also on their concentration and the incubation time. Agglomeration was much diminished in a medium containing serum. The protein corona formation depended on time and functionalization of NP, and varied significantly in different types of serum.ConclusionsSurface charge, ionic strength and biological molecules alter the properties of silica NPs and potentially affect their biological effects. The NPs surface in bovine serum and in human serum varies significantly, and it changes with incubation time. Consequently, the human serum, rather than the animal serum, should be used while conducting in vitro or in vivo studies concerning humans. Moreover, there is a need to pre-incubate NPs in the serum to control the composition of the bio-nano-composite that would be present in the human body.

It is increasingly recognized that nanoparticles (NPs) can 'age' while stored, and that the impact of this may lead to divergent results in terms of the observed toxicity of nominally the same NPs. The main goal of this study was to investigate whether (and to what extent) changes in silver (Ag) NPs' properties occur over time and whether storage of the dispersions under different conditions impacts their stability and ageing mechanism, as a function of the NPs' surface capping/charge. We found that both storage time/ conditions and surface chemistry of AgNPs influenced the evolution of the NP properties over time, and that the resulting changes in the NPs' physicochemical properties influenced their toxicity. Observed changes in Ag NPs' toxicity were related to different processes such as NP agglomeration, dissolution, oxidation, capping agent degradation as well attachment of Ag + ions to container walls. Thus, NP 'aging' effects as described here can be a significant contributor to the contradictory toxicity results observed in the literature for identical NPs, and NP ageing should thus be assessed in parallel with toxicity assessment as best practice.

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