There is a risk that poor toxicology studies could start undermining the success of nanomaterials, reports Elinor Hughes. Nanomaterials have been on the scene for over 15 years and they are being applied in a variety of sectors including coatings, textiles, energy, security, IT, food, cosmetics and medicine. Nanoparticles — particles in the 1—nm range — have unique properties compared to their larger counterparts such as the ability to squeeze into spaces inaccessible to larger particles. But with the research still in its infancy, their long-term effects on human health and the environment remain poorly understood.
Concerns have also been raised about the way nanomaterial toxicity data is reported. The end of the s saw considerable investment in new nanoscale materials thanks to their distinct properties.
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But, by creating these tiny particles, scientists were creating potential new ways for materials to interact with the human body and the environment. Every now and then, nano-related health-scare stories crop up. They observed that the nanoparticles can have an impact on the protein misfolding associated with the diseases. Nevertheless, the link had made newspaper headlines. Krug recently published a review in Angewandte Chemie called Nanoparticle research — are we on the right track?
In this he states that toxicology tests carried out on nanoparticles by researchers with no toxicology expertise are not fit for purpose. He scoured medical, pharmaceutical, toxicological and biological papers for tests done on nanoparticle uptake via the skin, the gastrointestinal tract and the lungs and found that most have serious errors.
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What they are doing is testing how a nanomaterial that gets into the body causes a biological effect, which is important in terms of human health implications, but a true toxicity test identifies the lethal dose, an intermediate dose and the dose with no effect. Krug revealed that there are examples of exposure studies in animals in which researchers have used grams of nanoparticles, which in many cases represents an overdose way above normal exposure levels.
One such study showed that cells treated with even a minor overdose of a nanomaterial in an in vitro test died because they were covered by agglomerated nanoparticles, which had cut off their nutrient and oxygen supplies. Results like this could give a false impression of the toxicity of the nanoparticle in question, as the true dose that the human body would be exposed to is not used. As Krug points out, if a human overdosed on common table salt, it would be fatal.
Some food packaging uses nanoparticles to impart resistance to heat, moisture and microbes. One reason that errors like this are being made is that a large number of groups carry out their toxicology studies without any knowledge about toxicology rules, explains Krug. This is a situation that he has tried to rectify.
In , as part of a European Commission funded project called Nanommune, Krug edited a handbook of standard procedures for nanoparticles testing that described ways to prepare nanomaterials for assays, how to prepare suspensions, how to do the toxicity assays and how to validate the toxicity assays. So the same mistakes that were made 10 years ago are being repeated again and again.
In industry, the aim is to develop safe and commercially viable products, so there are strict guidelines for toxicity tests such as those established by organisations such as the Organisation for Economic Co-operation and Development. Companies need to be sure that the toxicity or safety of a product complies with regulations, as well as with internal policies and values, to maintain brand trust, explains Maynard.
The plus side of this is that academics have the flexibility to develop novel practices that may be more appropriate.
Nurkiewicz says that the first things he looks at when reviewing a paper are the toxicological tests and safety data. Making sure everyone is on the same page in terms of sharing knowledge and getting the right equipment for tests takes money and this has been an problem.
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In , Maynard was part of a group pushing for increased government funding for nanomaterial safety tests. He says that there has been a significant jump in funding levels since then. The recipients of this funding vary. US research funding from agencies such as the National Institutes of Health typically goes to toxicology researchers who collaborate with groups synthesising materials.
Research funding in the US is available from federal agencies and professional associations to enable researchers to develop specific toxicological methods and techniques. Currently, competitive funds are available from societies such as the Society of Toxicology for synthetic chemists to better assess the toxicity of the nanoparticles they have created.
So investment is being made to ensure that testing methods could be standardised, but with nanotechnology research gathering pace as even more applications emerge, safeguarding their reputation for the future is paramount. Carbon nanotube can deliver cancer drugs right to the site of disease - but could they deliver harmful compounds too?
This largely positive public attitude towards nanomaterials has however meant they are now able to be investigated for use in medical applications unhindered, but this could lead to more stories appearing in the press. There are promising techniques for using them as carriers for drug delivery, in particular for treating cancer.
They can also be used as scaffolds inside the body to build up new bone or tissue.
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There are even soft nanomaterials made out of lipid- and silica-based materials that can dissolve over time to mimic biological materials for use in the body. Nanomaterials can also affect the environment in a positive way. These three-volumes provide coverage on organic light emitting diodes OLEDs and inorganic display devices including materials synthetic strategies, processing and fabrication methods, screening methods, spectroscopic characterization, energy transfer processes, luminescence in conjugated oligomers, polymers, nanostructured materials, carbon nanotubes, flexible display technologies, up-conversion phosphor materials and aging process, emissive displays display device reliability, electrode material degradation, packaging, surface properties, etc.
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