Nanotech filter may protect farmed fish from fungus


By Wagdy Sahel – SciDev.Net

Iranian scientists have coated a water filter with silver nanoparticles to prevent fungal infections in fish farmed indoors, in a step that they say could replace the direct release of nanoparticles into tanks — a process they have found is toxic to young rainbow trout.

The filter was developed following a study published in the Iranian Journal of Fisheries Sciences, which concluded that the direct application of ‘colloidal silver’ nanoparticles should no longer be allowed for fish, not least for rainbow trout, for which Iran is the world’s largest producer.

“We believe that the direct release of colloidal nanoparticles into the environment, especially in the aquaculture industry, must be prohibited,” Mohammad Reza Kalbassi, associate professor of aquaculture biotechnology at Tarbiat Modares University, Iran, and co-author of the study, tells SciDev.Net. “However, indirect use in a filter or via other instruments after scientific consideration may improve [the aquaculture] industry in future”.

The use of the new filter, made from nanosilver-coated minerals commonly used as commercial adsorbents, increased the survival rate of rainbow trout when compared with the control, Kalbassi says.

“In contrast to the control group, where around six per cent of fish had an infection caused by the fungus Saprolegnia, no infections were observed during the incubation period in the incubators containing nanosilver-coated filters,” he adds.

According to Kalbassi, the filter has been patented in Iran and details of its development will be published soon.

“I think that the silver nanoparticle filter has great potential for aquaculture,” says Irina Blinova, senior scientist at the laboratory of environmental toxicology, National Institute of Chemical Physics and Biophysics, Estonia.

But she points out that silver nanoparticles are toxic and their adsorption depends on factors such as time and the chemical composition of water. She recommends more research on the long-term effects of treated water on both the target fungi and aquatic species such as fish before the filter is used commercially.

Graeme Batley, chief research scientist at the catchment chemistry and ecotoxicology programme at Australia’s Commonwealth Scientific and Industrial Research Organisation, adds: “The first challenge to the filter system is to contain the nanoparticles without loss as the water is passed through.”

Batley says the passage of water is likely to cause a continuing release of low concentrations of ionic silver, whichmay lead to a “build-up of ionic silver that could become toxic with time”.

Link to full paper in the IranianJournalofFisheriesSciences

Previous articleStatement by the Press Secretary on the President’s Travel to Africa
Next articleSA: Sefa plans to lend over R737m to 15 000 small businesses
SciDev.Net is a not-for-profit organisation dedicated to providing reliable and authoritative information about science and technology for the developing world. Through our website we give policymakers, researchers, the media and civil society information and a platform to explore how science and technology can reduce poverty, improve health and raise standards of living around the world. We also build developing countries’ capacity for communicating science and technology through our regional networks of committed individuals and organisations, practical guidance and specialist workshops. SciDev.Net’s vision is to achieve better-informed decisions by individuals and organisations in the developing world on science and technology related issues, and thus the better integration of scientific knowledge and technological innovation into policies, programmes and projects intended to achieve sustainable development at all levels of society.