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“Toxicity depends on how much silver nanoparticles you feed into the cell. If it is a very small amount, it doesn’t show any toxicity. But if the concentration increases, the toxicity increases.”
-- Assoc Prof Suresh Valiyaveettil, Materials Research Lab. |
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When silver nanoparticles enter cells
RESEARCHERS at the NUS Materials Research Lab in the Department of Chemistry have found that silver nanoparticles present in wound dressing cause deformities in living tissues. Human cells and zebrafish are shown to develop toxicity when exposed to high concentration of silver nanoparticles.
Measuring less than 30 nanometers in size, these nanoparticles can travel through the air and water. They are present in common household products such as air or water filtration membranes, cosmetics and detergents. This means that they are able to enter environment and eventually into cellular systems of human and animals. What happen when these nanoparticles get into a cell?
The team led by Principal Investigator Assoc Prof Suresh Valiyaveettil and Ms AshaRani PV Nair, exposed human brain cells and fibroblast cells to silver nanoparticles and found presence of toxicity. The work was done in collaboration with Assoc Prof M Prakash Hande, Department of Physiology. The investigation progressed from a cell to a full living system. In another collaboration with Prof Gong Zhiyuan, Department of Biological Sciences, researchers fed silver nanoparticles into the medium containing zebrafish eggs – to observe for any changes in its physical body.
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| NANO RESEARCH: Ms AshaRani PV Nair, one of the researchers investigating the toxicity effects of silver nanoparticles.Inset: Normal development of zebrafish embryo (left). Deformities in embryo caused by nanoparticles (right). |
Zebrafish was chosen as it is transparent, allowing researchers to observe clearly the changes in its blood circulatory system and organs. Another advantage is that the development of egg to fish takes only three days. Researchers can hence monitor the entire process in the presence of silver nanoparticles. Results were startling: Some embryos had no eyes, while some had serious deformities. And some eggs died when the concentration of silver nanoparticles was increased.
The investigation did not stop here. The team was interested in unravelling the bio-chemical and molecular mechanism leading to these deformities. They wanted to find out how nanoparticles interact with living tissues. Their initial findings showed that when silver nanoparticles enter the human cells, they cause the production of reactive oxygen species or ROS which is known to cause damage to the DNA. They also investigated the toxicity of carbon nanotubes, common nanoparticles used in electrical circuits and as vessels for drug delivery. In zebrafish, the nanotubes tend to get embedded on the chorion, the membrane separating the embryo and mother. The researchers believe that the accumulation of nanotubes on the chorion hindered the transport of nutrients to the embryo, leading to toxicity and deformities.
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| POTENTIAL DANGER: Assoc Prof Suresh Valiyaveettil warned that factory workers who come into contact with heavy dosage of nanoparticles on a daily basis, need to be wary of possible danger. |
No cause for alarm
But there is no cause for alarm. You need not stop using wound dressing or detergent, as the concentration of silver nanoparticles found in household products are relatively low. Exposure time is also a factor. But Assoc Prof Suresh warned that factory workers who come into contact with heavy dosage of nanoparticles on a daily basis could well be in danger.
“Toxicity depends on how much silver nanoparticles you feed into the cell. If it is a very small amount, it doesn’t show any toxicity. But if the concentration increases, the toxicity increases,” he said.
The team will continue the research to further understand the mechanism of nanoparticles in living tissues.
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