A standardised approach for the dispersion of titanium dioxide nanoparticles in biological media

Abstract

We describe a comprehensive optimisation study culminating in a standardised and validated approach for the preparation of titanium dioxide (TiO₂) nanoparticle dispersions in relevant biological media. This study utilises a TiO₂ reference nanomaterial based on a commercially available powder that has been widely examined in both acute and chronic toxicity studies. The dispersion approach as presented here satisfies four key harmonisation requirements not previously addressed: (1) method transferability, based in part on the use of a sonication energy calibration method that allows for power measurement and reporting in a device-independent manner; (2) optimisation of sonication parameters and thorough method validation in terms of particle size distribution, pH, isoelectric point, concentration range and batch variability; (3) minimisation of sonolysis side effects by elimination of organics during sonication and (4) characterisation of nanoparticle agglomeration under various dispersion conditions by use of laser diffraction spectrometry, an in situ size characterisation technique that provides advantages over other techniques more commonly employed within the context of nanotoxicology (e.g. dynamic light scattering). The described procedure yields monomodal, nanoscale, protein-stabilised nanoparticle dispersions in biological media that remain stable for at least 48 h (acute testing timeframe) under typical incubation conditions.

Keywords::

• Nanomaterial
• agglomerate
• bovine serum albumin
• toxicology
• suspension

Acknowledgements

We thank Fred Klaessig of Pennsylvania Bio Nano Systems, LLC, for helpful suggestions and his critical review of the draft manuscript. We thank John Elliott, NIST Biochemical Science Division, for providing access to an incubator and for providing the DMEM-FBS test media used in this study. We thank Prof. Günter Oberdörster, University of Rochester, for sharing his P25 sample for validation tests. Evonik Industries AG is acknowledged for providing the P25 lot used in the OECD testing program. The authors acknowledge the contributions of Daniel Markwalter for his valuable assistance in conducting experimental tests under the sponsorship of NIST's Summer Undergraduate Research Fellowship (SURF) program, and participants of the International Alliance for NanoEHS Harmonization for many useful discussions, some of which helped motivate the current work.

Notes

¹The identification of any commercial product or trade name does not imply endorsement or recommendation by the National Institute of Standards and Technology.