Not ready to use – overcoming pitfalls when dispersing nanoparticles in physiological media

Abstract

Industrial nanoparticles are not developed to be compatible with in vitro cell culture assays which are carried out in isotonic solutions at physiological pH and often in the presence of proteins. The tendency of nanoparticles to deagglomerate or agglomerate is strongly sensitive to these parameters. The state of agglomeration and the protein corona bear an important influence on the level of toxic effects via the change of transport mechanisms and surface coating. Here we rigorously characterized the interaction of nanoparticles with physiological media for in vitro nanotoxicology experiments. Beyond adsorption of proteins on metal oxide and polymeric nanoparticles, we quantified nanoparticle deagglomeration due to adsorbing proteins acting as protection colloids. We report on previously neglected, but indispensable testing of sterility and measures to ensure it. Our findings result in a checklist of pre-requirements for dispersion of nanoparticles in physiological media and for reliable attribution of potential toxic effects.

Interaction of metal oxide nanoparticles with lung surfactant protein A

“…Dispersion of nanoparticles in protein solution can drastically alter the dispersion characteristics, leading to either increased or decreased particle sizes. We have previously demonstrated that the addition of Fetal Calf Serum leads to deagglomeration [1] and hence to smaller particle sizes for some of the particles tested here. Also, it could be demonstrated by Ehrenberg and coworkers that particles coated with serum proteins adsorbed onto endothelial cells in higher amounts as uncoated ones [2].…”

Testing Nanomaterial Toxicity in Unicellular Eukaryotic Algae and Fish Cell Lines

“…Be sure to exclude interferences of the NM with the assay ( see Subheading 3.6.1 ). Sterility of NM powders or suspensions can be achieved by autoclaving [ 22 , 29 ], γ-irradiation [ 30 ], or possibly fi ltration. However, one has to verify that these processes do not change NM properties or concentration.…”

“…However, one has to verify that these processes do not change NM properties or concentration. We have previously used X-ray photoelectron spectroscopy (XPS) to verify that γ-irradiation did not change the surface properties of diverse NM [ 30 ].…”

“…NMs have a high surface-to-volume ratio and possess specifi c physicochemical properties which make them prone to interfere with certain types of toxicity tests [ 30 ]. Possible interferences that need to be ruled out by appropriate cell-free controls are listed in Table 1 (also see Note 8 ).…”

Towards nanotechnology regulation – Publish the unpublishable

“…Nanomaterials are by no means "ready to use" in biological testing [2], thus they must be accurately characterized and tested under the conditions they are used in biological assays. As an example, data are often incomplete regarding the properties of nanomaterials upon contact with biological systems [3][4][5].…”