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In recent time, green synthesis of metal nanoparticles is the latest developing technology and received prodigious interest because it is easy, environmentally pristine, non-fouling, antitoxic, and lowcost approach. Green route of biogenic synthesis of metal nanoparticles via microbes such as bacteria, fungi, virus, yeast and algae has the potential to deliver sustainable and enviro safe protocol. Green synthesized metal nanoparticles are the most optimistic and novel agent for various catalytic and biological activities as antibacterial, antiviral, anticancer etc. without any toxic effects. Here, we reviewed algae-mediated green synthesis of metal and metal oxide nanoparticles and their biological activity. Algae are photoautotrophic, eukaryotic, aquatic, unicellular or multicellular organisms. Algae commonly used for biosynthesis because they grow rapidly, their biomass growth on average ten times faster than higher plants and easy to handle experiments with algal species. Different algal strains such as red, green and brown algae are using for the green synthesis of metal nanoparticles. Algae contain bioactive molecules and secondary metabolites that act as reducing, capping and stabilizing agent for manufacturing in nanoparticles. Biogenically synthesized metal and metal oxide nanoparticles characterized by different techniques such as UV-visible spectroscopy, SEM (scanning electron microscopy), HR-TEM (high-resolution transmission electron microscopy), XRD (X-ray diffraction), TGA (thermogravimetric analysis), DLS (dynamic light scattering) zeta potential and exhibited biological activity. In future, research algal production of metal nanoparticles can be explored by the use of different microalgae and their applications in different areas such as biological activity, catalytic activity in the synthesis of organic compounds, medical diagnose and synthesis of nanocomposite, lipid nanoparticles and antibiofilm.

OBJECTIVES: The spread of infectious diseases and the increase in drug resistance among microbes has forced researchers to synthesize biologically active nanoparticles. Ecofriendly procedures for the synthesis of nanoparticles are improving day by day in the field of nanobiotechnology. In the present study we used extract of the green alga Botryococcus braunii for the synthesis of palladium and platinum nanoparticles and evaluated their antimicrobial and antioxidant activity. MATERIALS AND METHODS: Green alga was collected from Udaisagar Lake, Udaipur (Rajasthan, India) and isolated by serial dilution method and grown on Chu-13 nutrient medium. The characterization of alga synthesized palladium and platinum nanoparticles was carried out using X-ray diffraction and scanning electron spectroscopy. The zone of inhibition was measured by agar well plate method and minimum inhibitory concentration was determined by agar dilution assay for antimicrobial activity. The antioxidant activity of the nanoparticles was also studied by 1,1-diphenyl-2-picrylhydrazyl method. RESULTS: Stable palladium and platinum nanoparticles were successfully produced using green alga. The XRD pattern revealed the crystalline nature and scanning electron micrographs showed the morphology of biogenically synthesized metal nanoparticles. Fourier transform infrared measurements showed all functional groups having control over stabilization and reduction of the nanoparticles. The green synthesized nanoparticles exhibited antimicrobial activity against gram-positive and gram-negative bacterial strains, antifungal activity against a fungus, and antioxidant activity. CONCLUSION: The biogenic synthesis of metal nanoparticles can be a promising process for the production of other transition metal nanoparticles and new nanocatalysts will revolutionize the synthesis of organic heterocycles.