New research has shown that extracts from a marine sponge could be used to make silver nanoparticles1. This technique offers a cost-effective and eco-friendly way to make silver nanoparticles, used in sensors and medical implants.

Synthesis of silver nanoparticles by chemical methods generates as by-products toxic chemicals that remain attached to the surface of the nanoparticles. Such nanoparticles are more likely to give adverse effects during biological applications. To overcome this drawback, researchers have used microorganisms such as bacteria and fungi to create silver nanoparticles. However, most such processes involve complex steps.

To find a simple, effective technique for producing silver nanoparticles, the researchers collected marine sponge (Acanthella elongata) from the Gulf of Mannar off the Tamil Nadu coast. They ground five grams of sponge and added water to yield a crude sponge extract. After filtering and further grinding, the sponge extract was added to silver nitrate solution at 45°C.

After 2 hours of reaction, the colour of the solution turned yellowish-brown, indicating the formation of silver nanoparticles. This phenomenon proved that silver ions were reduced to form silver nanoparticles in the sponge extract-containing solution. Sophisticated imaging techniques revealed the synthesis of spherical silver nanoparticles with diameters between 15 and 34 nanometre.

Water-soluble organic compounds such as amines present in sponge extract reduced the silver ions to silver nanoparticles.

Due to their antibacterial properties, silver nanoparticles could control the adhesion of microbes on metal surfaces. "This may be applicable to heat exchanger surfaces of power plants and medical implants of biomedical catheter," says lead researcher D. Inbakandan.

The authors of this work are from: Centre for Ocean Research, Sathyabama University, Rajiv Gandhi Salai (OMR), Marine Biology Regional Centre (ZSI) and National Institute of Ocean Technology, Pallikaranai, Chennai, and Centre of Advanced Study in Marine Biology, Annamalai University, Parangipettai , Tamil Nadu, India.

References
Inbakandan, D. et al. Marine sponge extract assisted biosynthesis of silver nanoparticles. Mater. Lett. 87, 66-68 (2012)