Background: Nanotechnology opens new applications in many fields including medicine. Among all metallic nanoparticles, silver nanoparticles (silver NPS) have proved to be the most effective against a large variety of organisms including toxic cyanobacteria. Materials and
Methods: Silver NPs were biosynthesized in vivo with different alga species namely, Spirulina platensis, Chlorella vulgaris and Scenedesmus obliquus following two scenarios. First: by suspending a thoroughly washed algae biomass in 1 mM aqueous AgNO3 solution. Second:by culturing them individually in culture media containing the same concentration of AgNO3. Silver NPs were characterized using UV-Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive analysis (EDX) and Fourier transform infra-red (FTIR) spectroscopy. The biosynthesized silver NPs were tested for cytotoxic activity against a cancer promoter cyanobacteruim Microcystis aeruginosa, considering effects on cell viability and chlorophyll content.
Results: The surface plasmon band indicated the biosynthesis of silver NPs at ~400 nm. Transmission electron microscopy (TEM) revealed that the silver NPs had a mean average size below 100 nm. Energy-dispersive analysis X-ray (EDX) spectra confirmed the presence of silver element. FTIR spectralanalyses suggested that proteins and or polysaccharides may be responsible for the biosynthesis of silver NPs and (-COO-) of carboxylate ions is responsible for stabilizing them. The toxic potentialities of the biosynthesized silver NPs against the cancer promoter cyanobacterium, Microcystis aeruginosa showed high reduction in viable cells count and the total chlorophyll content.
Conclusions: The potential activity of the biosynthesized silver NPs from the studied algae species against Microcystis aeruginosa cells is expected to be mainly mediated by therelease of silver ions (Ag+) from the particle surface and bioactive compounds as indicated by FTIR analysis.