Abstract:The synthesis of gold and silver nanoparticles by the blue-green algae Spirulina platensis for medical purposes was studied. A complex of optical and analytical methods was used in order to characterize produced nanoparticles. It was shown that the extracellular formation of metal nanoparticles of spherical shape with sizes in the range between 8 and 40 nm (the average size of 20-30 nm) takes place. The characteristics of gold and silver nanoparticles in the Spirulina biomass were compared. The role of biosorption processes in the synthesis of nanoparticles was estimated by using equilibrium dialysis. A positive influence of sonication on the process of microbial synthesis and yield of nanoparticles were demonstrated. The neutron activation analysis and the atomic absorption spectrometry were applied for characterizing the dynamics of gold and silver nanoparticles formation in the Spirulina platensis biomass. The neutron activation analysis was used for studying the elemental content of the Spirulina platensis biomass.
Several bacterial strains of Actinomycetes belonging to Streptomyces and Arthrobacter genera for the first time were used to study the biotechnology of synthesis of gold and silver nanoparticles. The experimental conditions of gold and silver nanoparticles production by the cells of studied strains in aqueous chloroauric acid (HAuCl 4 ) and in silver nitrate (AgNO 3 ) solutions, respectively, were determined. Concentration and time-dependences of nanoparticle formation were investigated. The complex of optical and analytical methods was used for testing the gold and silver nanoparticles in the bacterial biomass. The TEM (Transmission Electron Microscopy) and XRD (X-ray Diffraction) data in all cases demonstrated the presence of crystals with fcc (face centered cubic) structure. The results obtained show that the Actinomycetes are capable of producing gold and silver nanoparticles of spherical shape extracellularly when exposed to suitable compounds. The particle size distribution shows that the sizes of nanoparticles are in the range of 5 nm to 80 nm. The biomass obtained may be used for industrial as well as medical and pharmaceutical purposes.
Effect of toxic metal ions Cd(II) and Pb(II) on cyanobacterium (blue-green algae) Spirulina platensis intact cells have been studied with optical and differential scanning microcalorimetry (DSC) methods after 7.2 kGy 137 Cs gamma irradiation and without irradiation. It is shown that the addition of metal ions causes a decrease in optical absorption spectra band intensities. In the case of irradiation, the absorption band intensity decreases higher than without irradiation. The binding constant of Pb(II) with Spirulina platensis is calculated for nutrition medium with pH 9.2. DSC data show that Cd(II) and Pb(II) ions do not change the integral heat of absorption (ΔHm) that equals to 24.6 J g -1 . In the case of irradiation, the DSC melting curve profile changes significantly and ΔHm decreases two times, which indicates that 50 % of proteins are denaturated. The DSC method also gives a possibility to evaluate C-phycocyanin content from deconvoluted heat absorption peak at 50 °C, which equals to 35.5 %. In case of irradiated wet mass, sub-cultured wet mass, and wet mass re-irradiated with the same dose, contents of Spirulina platensis ingredients -C-phycocyanin, chlorophyll, and carotenoidsincrease as a result of the simultaneous effect of the metal ions and irradiation.
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