Behavior of TiO₂ Released from Nano-TiO₂‑Containing Paint and Comparison to Pristine Nano-TiO₂

In the assessment of the fate and effects of engineered nanomaterials (ENM), the current focus is on studying the pristine, unaltered materials. However, ENM are incorporated into products and are released over the whole product life cycle, though mainly during the use and disposal phases. So far, released ENMs have only been characterized to a limited extent and almost nothing is known about the behavior of these materials under natural conditions. In this work we obtained material that was released from aged paint containing nano-TiO₂, characterized the particulate materials, and studied their colloidal stability in media with different pH and ionic composition. A stable suspension was obtained from aged paint powder by gentle shaking in water, producing a dilute suspension of 580 μg/L TiO₂ with an average particle size of 200–300 nm. Most particles in this suspension were small pieces of paint matrix that also contained nano-TiO₂. Some free nano-TiO₂ particles were observed by electron microscopy, but the majority was enclosed by the organic paint binder. The pristine nano-TiO₂ showed the expected colloidal behavior with increasing stability with increasing pH and strong agglomeration above the isoelectric point and settling in the presence of Ca. The released TiO₂ showed very small variations in particle size, ζ potential, and colloidal stability, even in the presence of 3 mM Ca. The results show that the behavior of released ENM may not necessarily be predicted by studying the pristine materials. Additionally, effect studies need to focus more on the particles that are actually released as we can expect that the toxic effect will also be markedly different between pristine and product released materials

Body distribution of SiO₂–Fe₃O₄ core-shell nanoparticles after intravenous injection and intratracheal instillation

<p>Nano-silicon dioxide (SiO₂) is used nowadays in several biomedical applications such as drug delivery and cancer therapy, and is produced on an industrial scale as additive to paints and coatings, cosmetics and food. Data regarding the long-term biokinetics of SiO₂ engineered nanoparticles (ENPs) is lacking. In this study, the whole-body biodistribution of SiO₂ core-shell ENPs containing a paramagnetic core of Fe₃O₄ was investigated after a single exposure via intravenous injection or intratracheal instillation in mice. The distribution and accumulation in different organs was evaluated for a period of 84 days using several techniques, including magnetic resonance imaging, inductively coupled plasma mass spectrometry, X-ray fluorescence and X-ray absorption near edge structure spectroscopy. We demonstrated that intravenously administered SiO₂ ENPs mainly accumulate in the liver, and are retained in this tissue for over 84 days. After intratracheal instillation, an almost complete particle clearance from the lung was seen after 84 days with distribution to spleen and kidney. Furthermore, we have strong evidence that the ENPs retain their original core-shell structure during the whole observation period. This work gives an insight into the whole-body biodistribution of SiO₂ ENPs and will provide guidance for further toxicity studies.</p