Research Highlight

Marine algae shape nanoparticles

doi:10.1038/nindia.2011.22 Published online 15 February 2011

New research has shown that a compound isolated from a species of red marine algae can help synthesize silver nanoparticles with antibacterial properties — an eco-friendly technique that may have a variety of potential biomedical applications.

Silver nanoparticles have been studied extensively in recent years for their wide range of applications as catalysts, biosensors and antibacterials. However, the synthesis of silver nanoparticles requires harsh reducing and stabilizing agents, making them unsuitable for biological applications.

Making silver nanoparticles using natural microorganisms such as bacteria and fungi is tedious and slow. To devise a faster, environmentally friendly fabrication technique, the researchers turned their attention to natural microorganisms present in the sea. The researchers isolated a sulphated polysaccharide from a red marine alga (Porphyra vietnamensis) that helped synthesize silver nanoparticles with an average size of 13 nm.

When tested for antibacterial properties, the nanoparticles caused 100% inhibition of E. coli growth at a dose of 5 μg l–1 and 60% inhibition of Staphylococcus aureus growth at a dose of 15 μg l–1.

This improved activity against E. coli may be due to the fast internalization of nanoparticles in the cell walls of bacteria, leading to fast inactivation of the protein structure and eventually cell death.

"The amazing antibacterial properties of these nanoparticles allow them to be used for a variety of applications, including tropical antibacterial creams or lotions, fibres, candles in water filter and food packaging," says lead researcher Varsha B. Pokharkar.


  1. Venkatpurwar, V. et al. Green synthesis of silver nanoparticles using marine polysaccharide: study of in-vitro antibacterial activity. Mater. Lett. 65, 999-1002 (2011) | Article