Using aqueous cyanobacterial extracts in the synthesis of silver nanoparticle is looked as green, ecofriendly, low priced biotechnology that gives advancement over both chemical and physical methods. In the current study, an aqueous extract of Oscillatoria limnetica fresh biomass was used for the green synthesis of Ag-NPs, since O. limnetica extract plays a dual part in both reducing and stabilizing Oscillatoria-silver nanoparticles (O-AgNPs). The UV-Visible absorption spectrum, Fourier transforms infrared (FT-IR), transmission electron microscopy (TEM) and scanning electron microscope (SEM) were achieved for confirming and characterizing the biosynthesized O-AgNPs. TEM images detected the quasi-spherical Ag-NPs shape with diverse size ranged within 3.30–17.97 nm. FT-IR analysis demonstrated the presence of free amino groups in addition to sulfur containing amino acid derivatives acting as stabilizing agents as well as the presence of either sulfur or phosphorus functional groups which possibly attaches silver. In this study, synthesized Ag-NPs exhibited strong antibacterial activity against multidrug-resistant bacteria (Escherichia coli and Bacillus cereus) as well as cytotoxic effects against both human breast (MCF-7) cell line giving IC50 (6.147 µg/ml) and human colon cancer (HCT-116) cell line giving IC50 (5.369 µg/ml). Hemolytic activity of Ag-NPs was investigated and confirmed as being non- toxic to human RBCs in low concentrations.

In recent decades, researchers were attracted towards cyanobacterial components which are potential low-cost biological reagents for silver nanoparticle biosynthesis. This article describes the biological synthesis of silver nanoparticles using a proteinaceous pigment phycocyanin extracted from Nostoc linckia as reducing agent. The synthesized silver nanoparticles have a surface plasmon resonance band centered at 425 nm. Face-centered central composite design used for optimization of silver nanoparticles (AgNPs) biosynthesis using phycocyanin. The maximum AgNPs biosynthesis obtained using the optimized four variables, initial pH level (10), AgNO3 concentration (5 mM), phycocyanin pigment concentration (1 mg/mL) and incubation period (24 h) was 1100.025 µg/mL. The TEM analysis of AgNPs showed spherical nanoparticles with mean size between 9.39 to 25.89 nm. FTIR spectra showed major peaks of proteins involved in AgNPs biosynthesis by identifying different functional groups involved in effective capping of AgNPs. The biosynthesized AgNPs significantly inhibited the growth of medically important pathogenic Gram-positive (Staphylococcus aureus), Gram-negative bacteria (Pseudomonas aeruginosa, E. coli and Klebsiella pneumonia). The synthesized AgNPs exhibited effective cytotoxic activity against MCF-7 and the inhibitory concentration (IC50) was recorded at 27.79 ± 2.3 µg/mL. The in vivo studies clearly indicated that AgNPs has a capacity to inhibit the growth of tumor in Ehrlich ascites carcinoma bearing mice.

Phycoerythrin is the main phycobiliprotein that responsible for harvesting light for photosynthesis in cyanobacteria. In this research, phycoerythrin extracted from the cyanobacterium Nostoc carneum has been used to reduce silver nitrate for silver nanoparticles (AgNPs) biosynthesis. UV–visible spectrophotometry for measuring surface plasmon resonance showed a single absorption peak at 430 nm, which confirmed the presence of AgNPs. The face-centered central composite design was chosen to evaluate the interaction effects between four process variables and also to determine their optimal levels which influence the AgNPs biosynthesis using phycoerythrin. The maximum silver nanoparticles biosynthesis (1733.260 ± 21 µg/mL) was achieved in the central runs under the conditions of initial pH 10, incubation period of the 24 h, phycoerythrin concentration of the 0.8 mg/mL and 20 mM of AgNO3. The biosynthesized AgNPs were characterized using TEM which revealed the formation of spherical shape nanoparticles with size ranged between 7.1‒26.68 nm. EDX analysis confirmed silver as the major constituent element. FTIR spectrum indicates the presence of proteinaceous capping agent that prevents silver nanoparticles agglomeration. The IC50 of cell inhibition by AgNPs was observed at 13.07 ± 1.1 µg/mL. Treatment of mice bearing Ehrlich ascites carcinoma with 5 mg AgNPs/kg of mice body weight significantly decreased tumor volume, tumor cells count, white blood cells count and body weight. It was concluded that the phycoerythrin protein has the ability to synthesize AgNPs, which have antibacterial, antihemolytic, in vitro and in vivo cytotoxic activities.

Chlorella vulgaris, like a wide range of other microalgae, are able to grow mixotrophically. this maximizes its growth and production of polysaccharides (pS). the extracted polysaccharides have a complex monosaccharide composition (fructose, maltose, lactose and glucose), sulphate (210.65 ± 10.5 mg g −1 PS), uronic acids (171.97 ± 5.7 mg g −1 pS), total protein content (32.99 ± 2.1 mg g −1 PS), and total carbohydrate (495.44 ± 8.4 mg g −1 pS). fourier transform infrared spectroscopy (ft-iR) analysis of the extracted polysaccharides showed the presence of n-H, o-H, c-H,-cH 3 , >cH 2 , coo −1 , S=o and the c=o functional groups. UV-Visible spectral analysis shows the presence of proteins, nucleic acids and chemical groups (ester, carbonyl, carboxyl and amine). Purified polysaccharides were light green in color and in a form of odorless powder. it was soluble in water but insoluble in other organic solvents. thermogravimetric analysis demonstrates that Chlorella vulgaris soluble polysaccharide is thermostable until 240°C and degradation occurs in three distinct phases. Differential scanning calorimetry (DSC) analysis showed the characteristic exothermic transition of Chlorella vulgaris soluble polysaccharides with crystallization temperature peaks at 144.1°C, 162.3°C and 227.7°C. The X-ray diffractogram illustrated the semicrystalline nature of these polysaccharides. Silver nanoparticles (Agnps) had been biosynthesized using a solution of Chlorella vulgaris soluble polysaccharides. the pale green color solution of soluble polysaccharides was turned brown when it was incubated for 24 hours with 100 mM silver nitrate in the dark, it showed peak maximum located at 430 nm. FT-IR analysis for the biosynthesized AgNPs reported the presence of carbonyl,-CH 3 , >cH 2 , c-H,-oH and-nH functional groups. Scanning and transmission electron microscopy show that Agnps have spherical shape with an average particle size of 5.76. Energy-dispersive X-ray (EDX) analysis showed the dominance of silver. the biosynthesized silver nanoparticles were tested for its antimicrobial activity and have positive effects against Bacillus sp., Erwinia sp., Candida sp. priming seeds of Triticum vulgare and Phaseolus vulgaris with polysaccharides solutions (3 and 5 mg mL −1) resulted in significant enhancement of seedling growth. increased root length, leaf area, shoot length, photosynthetic pigments, protein content, carbohydrate content, fresh and dry biomass were observed, in addition these growth increments may be attributed to the increase of antioxidant activities. Microalgae are some of the oldest, most economically promising organisms in the world 1 and one of the richest sources of protein in addition to polysaccharides, carotenoids, phycobiliproteins, polysaccharides, vitamins and

The physico-chemical characterization of the cyanobacterium Nostoc carneum extracellular polysaccharide (EPS) was studied. Two sugars moieties glucose (105.5 mg gG 1 EPS) and xylose (215.2 mg gG 1 EPS) were involved in the polysaccharide composition as well as the presence of sulfate, uronic acids and protein. The in vitro antioxidant assays (reducing power and DPPH) showed that N. carneum EPS possess antioxidant activity. Fourier Transformed Infrared (FT-IR) spectra of EPS showed a specific absorbance of O-H and-NH stretching, asymmetrical-symmetrical C-H stretching, Presence of sulfur containing functional groups and carboxylic acids. The thermal gravimetric and differential scanning calorimetric analyses confirmed that polysaccharide thermal stability was around 237°C. Nostoc carneum exopolymer showed pseudoplastic non-Newtonian fluid behavior in the aqueous solutions as well as increasing viscosity with increasing concentration.