Tag Archives: titanium dioxide (TiO2) nanoparticles

Canadian research into nanomaterial workplace exposure in the air and on surfaces

An August 30, 2018 news item on Nanowerk announces the report,

The monitoring of air contamination by engineered nanomaterials (ENM) is a complex process with many uncertainties and limitations owing to the presence of particles of nanometric size that are not ENMs, the lack of validated instruments for breathing zone measurements and the many indicators to be considered.

In addition, some organizations, France’s Institut national de recherche et de sécurité (INRS) and Québec’s Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST) among them, stress the need to also sample surfaces for ENM deposits.

In other words, to get a better picture of the risks of worker exposure, we need to fine-tune the existing methods of sampling and characterizing ENMs and develop new one. Accordingly, the main goal of this project was to develop innovative methodological approaches for detailed qualitative as well as quantitative characterization of workplace exposure to ENMs.

A PDF of the 88-page report is available in English or in French.

An August 30, 2018 (?) abstract of the IRSST report titled An Assessment of Methods of Sampling and Characterizing Engineered Nanomaterials in the Air and on Surfaces in the Workplace (2nd edition) by Maximilien Debia, Gilles L’Espérance, Cyril Catto, Philippe Plamondon, André Dufresne, Claude Ostiguy, which originated the news item, outlines what you can expect from the report,

This research project has two complementary parts: a laboratory investigation and a fieldwork component. The laboratory investigation involved generating titanium dioxide (TiO2) nanoparticles under controlled laboratory conditions and studying different sampling and analysis devices. The fieldwork comprised a series of nine interventions adapted to different workplaces and designed to test a variety of sampling devices and analytical procedures and to measure ENM exposure levels among Québec workers.

The methods for characterizing aerosols and surface deposits that were investigated include: i) measurement by direct-reading instruments (DRI), such as condensation particle counters (CPC), optical particle counters (OPC), laser photometers, aerodynamic diameter spectrometers and electric mobility spectrometer; ii) transmission electron microscopy (TEM) or scanning transmission electron microscopy (STEM) with a variety of sampling devices, including the Mini Particle Sampler® (MPS); iii) measurement of elemental carbon (EC); iv) inductively coupled plasma mass spectrometry (ICP-MS) and (v) Raman spectroscopy.

The workplace investigations covered a variety of industries (e.g., electronics, manufacturing, printing, construction, energy, research and development) and included producers as well as users or integrators of ENMs. In the workplaces investigated, we found nanometals or metal oxides (TiO2, SiO2, zinc oxides, lithium iron phosphate, titanate, copper oxides), nanoclays, nanocellulose and carbonaceous materials, including carbon nanofibers (CNF) and carbon nanotubes (CNT)—single-walled (SWCNT) as well as multiwalled (MWCNT).

The project helped to advance our knowledge of workplace assessments of ENMs by documenting specific tasks and industrial processes (e.g., printing and varnishing) as well as certain as yet little investigated ENMs (nanocellulose, for example).

Based on our investigations, we propose a strategy for more accurate assessment of ENM exposure using methods that require a minimum of preanalytical handling. The recommended strategy is a systematic two-step assessment of workplaces that produce and use ENMs. The first step involves testing with different DRIs (such as a CPC and a laser photometer) as well as sample collection and subsequent microscopic analysis (MPS + TEM/STEM) to clearly identify the work tasks that generate ENMs. The second step, once work exposure is confirmed, is specific quantification of the ENMs detected. The following findings are particularly helpful for detailed characterization of ENM exposure:

  1. The first conclusive tests of a technique using ICP-MS to quantify the metal oxide content of samples collected in the workplace
  2. The possibility of combining different sampling methods recommended by the National Institute for Occupational Safety and Health (NIOSH) to measure elemental carbon as an indicator of NTC/NFC, as well as demonstration of the limitation of this method stemming from observed interference with the black carbon particles required to synthesis carbon materials (for example, Raman spectroscopy showed that less than 6% of the particles deposited on the electron microscopy grid at one site were SWCNTs)
  3. The clear advantages of using an MPS (instead of the standard 37-mm cassettes used as sampling media for electron microscopy), which allows quantification of materials
  4. The major impact of sampling time: a long sampling time overloads electron microscopy grids and can lead to overestimation of average particle agglomerate size and underestimation of particle concentrations
  5. The feasibility and utility of surface sampling, either with sampling pumps or passively by diffusion onto the electron microscopy grids, to assess ENM dispersion in the workplace

These original findings suggest promising avenues for assessing ENM exposure, while also showing their limitations. Improvements to our sampling and analysis methods give us a better understanding of ENM exposure and help in adapting and implementing control measures that can minimize occupational exposure.

You can download the full report in either or both English and French from the ‘Nanomaterials – A Guide to Good Practices Facilitating Risk Management in the Workplace, 2nd Edition‘ webpage.

What helps you may hurt you (titanium dioxide nanoparticles and orthopedic implants)

From a Sept. 16, 2017 news item on Nanotechnology Now,

Researchers from the Mayo Clinic have proposed that negative cellular responses to titanium-based nanoparticles released from metal implants interfere in bone formation and resorption at the site of repair, resulting in implant loosening and joint pain. [emphasis mine]Their review of recent scientific evidence and call for further research to characterize the biological, physical, and chemical interactions between titanium dioxide nanoparticles and bone-forming cells is published in BioResearch Open Access, a peer-reviewed open access journal from Mary Ann Liebert, Inc., publishers. The article is available free on theBioResearch Open Access website.

A Sept. 14, 2017 Mary Anne Liebert (Publishing) news release, which originated the news item,  mentions the authors,

Jie Yao, Eric Lewallen, PhD, David Lewallen, MD, Andre van Wijnen, PhD, and colleagues from the Mayo Clinic, Rochester, MN and Second Affiliated Hospital of Soochow University, China, coauthored the article entitled “Local Cellular Responses to Titanium Dioxide from Orthopedic Implants The authors examined the results of recently published studies of titanium-based implants, focusing on the direct and indirect effects of titanium dioxide nanoparticles on the viability and behavior of multiple bone-related cell types. They discuss the impact of particle size, aggregation, structure, and the specific extracellular and intracellular (if taken up by the cells) effects of titanium particle exposure.

“The adverse effects of metallic orthopedic particles generated from implants are of significant clinical interest given the large number of procedures carried out each year. This article reviews our current understanding of the clinical issues and highlights areas for future research,” says BioResearch Open Access Editor Jane Taylor, PhD, MRC Centre for Regenerative Medicine, University of Edinburgh, Scotland.

Before getting to the abstract, here’s a link to and a citation for the paper,

Local Cellular Responses to Titanium Dioxide from Orthopedic Implants by Yao, Jie J.; Lewallen, Eric A.; Trousdale, William H.; Xu, Wei; Thaler, Roman; Salib, Christopher G.; Reina, Nicolas; Abdel, Matthew P.; Lewallen, David G.; and van Wijnenm, Andre J.. BioResearch Open Access. July 2017, 6(1): 94-103. https://doi.org/10.1089/biores.2017.0017 Published July 1, 2017

This paper is open access.

Titanium dioxide nanoparticles have subtle effects on oxidative stress genes?

There’s research from the Georgia Institute of Technology (Georgia Tech; US) suggesting that titanium dioxide nanoparticles may have long term side effects. From a May 10, 2016 news item on ScienceDaily,

A nanoparticle commonly used in food, cosmetics, sunscreen and other products can have subtle effects on the activity of genes expressing enzymes that address oxidative stress inside two types of cells. While the titanium dioxide (TiO2) nanoparticles are considered non-toxic because they don’t kill cells at low concentrations, these cellular effects could add to concerns about long-term exposure to the nanomaterial.

A May 9, 2016 Georgia Tech news release on Newswire (also on EurekAlert), which originated the news item, describes the research in more detail,

Researchers at the Georgia Institute of Technology used high-throughput screening techniques to study the effects of titanium dioxide nanoparticles on the expression of 84 genes related to cellular oxidative stress. Their work found that six genes, four of them from a single gene family, were affected by a 24-hour exposure to the nanoparticles.

The effect was seen in two different kinds of cells exposed to the nanoparticles: human HeLa* cancer cells commonly used in research, and a line of monkey kidney cells. Polystyrene nanoparticles similar in size and surface electrical charge to the titanium dioxide nanoparticles did not produce a similar effect on gene expression.

“This is important because every standard measure of cell health shows that cells are not affected by these titanium dioxide nanoparticles,” said Christine Payne, an associate professor in Georgia Tech’s School of Chemistry and Biochemistry. “Our results show that there is a more subtle change in oxidative stress that could be damaging to cells or lead to long-term changes. This suggests that other nanoparticles should be screened for similar low-level effects.”

The research was reported online May 6 in the Journal of Physical Chemistry C. The work was supported by the National Institutes of Health (NIH) through the HERCULES Center at Emory University, and by a Vasser Woolley Fellowship.

Titanium dioxide nanoparticles help make powdered donuts white, protect skin from the sun’s rays and reflect light in painted surfaces. In concentrations commonly used, they are considered non-toxic, though several other studies have raised concern about potential effects on gene expression that may not directly impact the short-term health of cells.

To determine whether the nanoparticles could affect genes involved in managing oxidative stress in cells, Payne and colleague Melissa Kemp – an associate professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University – designed a study to broadly evaluate the nanoparticle’s impact on the two cell lines.

Working with graduate students Sabiha Runa and Dipesh Khanal, they separately incubated HeLa cells and monkey kidney cells with titanium oxide at levels 100 times less than the minimum concentration known to initiate effects on cell health. After incubating the cells for 24 hours with the TiO2, the cells were lysed and their contents analyzed using both PCR and Western Blot techniques to study the expression of 84 genes associated with the cells’ ability to address oxidative processes.

Payne and Kemp were surprised to find changes in the expression of six genes, including four from the peroxiredoxin family of enzymes that helps cells degrade hydrogen peroxide, a byproduct of cellular oxidation processes. Too much hydrogen peroxide can create oxidative stress which can damage DNA and other molecules.

The effect measured was significant – changes of about 50 percent in enzyme expression compared to cells that had not been incubated with nanoparticles. The tests were conducted in triplicate and produced similar results each time.

“One thing that was really surprising was that this whole family of proteins was affected, though some were up-regulated and some were down-regulated,” Kemp said. “These were all related proteins, so the question is why they would respond differently to the presence of the nanoparticles.”

The researchers aren’t sure how the nanoparticles bind with the cells, but they suspect it may involve the protein corona that surrounds the particles. The corona is made up of serum proteins that normally serve as food for the cells, but adsorb to the nanoparticles in the culture medium. The corona proteins have a protective effect on the cells, but may also serve as a way for the nanoparticles to bind to cell receptors.

Titanium dioxide is well known for its photo-catalytic effects under ultraviolet light, but the researchers don’t think that’s in play here because their culturing was done in ambient light – or in the dark. The individual nanoparticles had diameters of about 21 nanometers, but in cell culture formed much larger aggregates.

In future work, Payne and Kemp hope to learn more about the interaction, including where the enzyme-producing proteins are located in the cells. For that, they may use HyPer-Tau, a reporter protein they developed to track the location of hydrogen peroxide within cells.

The research suggests a re-evaluation may be necessary for other nanoparticles that could create subtle effects even though they’ve been deemed safe.

“Earlier work had suggested that nanoparticles can lead to oxidative stress, but nobody had really looked at this level and at so many different proteins at the same time,” Payne said. “Our research looked at such low concentrations that it does raise questions about what else might be affected. We looked specifically at oxidative stress, but there may be other genes that are affected, too.”

Those subtle differences may matter when they’re added to other factors.

“Oxidative stress is implicated in all kinds of inflammatory and immune responses,” Kemp noted. “While the titanium dioxide alone may just be modulating the expression levels of this family of proteins, if that is happening at the same time you have other types of oxidative stress for different reasons, then you may have a cumulative effect.”

*HeLa cells are named for Henrietta Lacks who unknowingly donated her immortal cell line to medical research. You can find more about the  story on the Oprah Winfrey website, which features an excerpt from the Rebecca Skloot book “The Immortal Life of Henrietta Lacks.” By the way, on May 2, 2016 it was announced that Oprah Winfrey would star in a movie for HBO as Henrietta Lacks’ daughter in an adaptation of the Rebecca Skloot book. You can read more about the proposed production in a May 3, 2016 article by Benjamin Lee for the Guardian.

Getting back to titanium dioxide nanoparticles and their possible long term effects, here’s a link to and a citation for the Georgia Tech team’s paper,

TiO2 Nanoparticles Alter the Expression of Peroxiredoxin Antioxidant Genes by Sabiha Runa, Dipesh Khanal, Melissa L. Kemp‡, and Christine K. Payne. J. Phys. Chem. C, Article ASAP DOI: 10.1021/acs.jpcc.6b01939 Publication Date (Web): April 21, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.