Halloysite nanotubes (HNT) are products of nature. In chemical composition they are similar to kaolin and can be considered as rolled kaolin sheets with inner diameter of 10-20 nm, outer diameter of 40-70 nm and a length of 500-1500 nm. The internal side of halloysite is composed of Al2O3 while the external is mainly SiO2.
These clay tubes are excavated from mines as stone minerals and processed by milling to form fine power of tubes, which is then used to dope a variety of polymers. The polymer doping has been observed to enhance various properties of these polymers including strength, adhesivity and flame retardancy. In addition, the large surface area and oppositely charged inner and out diameter facilitate loading a variety of biomolecules useful in medical applications. Given this wide range of applications there is an inevitable release of these materials back to the environment in this refined forms.
Despite the many reports on in vitro toxicity of HNTs, there is only limited information available with regard to its in vivo toxicity. Therefore, to shed light on this matter., Professor Fakhrullin and colleagues at Kazan Federal University investigated for the first time the in vivo toxicity of HNT using Caenorhabditis elegans nematode as a model organism. The C. elegans are an important tool in molecular biology because its fully sequenced genome is closely homologous to the human genome.
The findings of this research has shown that the primary pathway of the HNT entry into the organism is the intestinal uptake. The toxic effects of HNT uptake was then investigated by comparing the body size, fertility (or the number of eggs laid in other words) and longevity of the nematodes.
These comparisons did not give statistically significant differences between the controls, which suggests that these are potentially environmentally safe materials to work with. This is in fact is in contrast to the toxicities observed with other nanomaterials such as single walled carbon nanotubes (SWCNTS), graphene oxides, TiO2 nanoparticles and platinum nanoparticles.
Even coating the nematode eggs with the HNT did not result in any significant deviations from the control nematodes. At extremely high doses of HNT did inflict some mechanical stress on the alimentary systems but these levels are highly unlikely to be encountered under environmentally relevant conditions.
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Toxicity of halloysite clay nanotubes in vivo: A Caenorhabditis elegans study
Gölnur I. Fakhrullina, Farida S. Akhatova, Yuri M. Lvov and Rawil F. Fakhrullin
Environ. Sci.: Nano, 2015, 2, 54-59
DOI: 10.1039/C4EN00135D
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About the webwriter
Imali Mudunkotuwa is a Postdoctoral Scholar and Research Assistant at The University of Iowa. She is interested in nanoscience, physical and surface chemistry. You can find more articles by Imali in her author archive .
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