Biogenic synthesis of gold nanoparticle using fractioned cellular components from eukaryotic algae and cyanobacteria

Abstract

SummaryIn the present investigation fractioned cellular components like intact pigment bearing thylakoids/chloroplasts, carotenoids, protein, polysaccharides were extracted from the cyanobacterium Anabaena sphaerica and green alga Chlorococcum infusionum. Each of these extracts was used separately in search for efficient reducing agents during gold nanoparticle (GNP) production in pro‐ and eukaryotic algal cell systems. The whole biomass and extracted compounds or cellular structures were exposed in 25 mg L−1 aqueous hydrogen tetrachloroaurate solutions separately at room temperature. Isolated viable chloroplasts from C. infusionum and thylakoids from A. sphaerica were found to be able to reduce gold ions. The protein extracts of both strains were also able to synthesize GNP at 4°C. Extracted polysaccharides of the two strains responded differently. Polysaccharides from A. sphaerica showed positive response in GNP synthesis, whereas no change was observed for C. infusionum. The carotenoids extracts from both strains acted like an efficient reducing agent. Initially the reducing efficiency of these extracted components was confirmed by the appearance of purple color in biomass or in experimental media. The GNPs, synthesized within the biomass were extracted by sonication with sodium citrate. The UV–vis spectroscopy of extracted purple colored suspensions and media showed the absorption bands at approximately 530–540 nm indicating a strong positive signal of GNP synthesis. Transmission electro n microscopy determined the size and shapes of the particles. The X‐ray diffraction study of the synthesized GNP revealed that the 2θ values appeared at 38.2°, 44.5°, 64.8° and 77.8°. Amongst all, isolated thylakoids and chloroplast showed only spherical GNP production with variable size range at pH 4. Monodisperse GNPs were also synthesized by isolated thylakoids and chloroplast at pH 9. A detailed morphological change of gold treated biomass was revealed employing scanning electron microscopy. The fluorescent property of gold loaded cells was studied by fluorescence microscopy.