Eco-friendly synthesis of silver nanoparticles from filamentous cyanobacteria Arthrospira platensis phycocyanin and its antifungal and antibacterial activities

• Nanoparticles were characterized using FT-IR, DLS, SEM, and TEM techniques. • Significant antifungal activity was observed against Aspergillus fumigatus and Fusarium oxysporum . Silver nanoparticles have gained significant attention due to their remarkable antibacterial and antifungal properties, making them a promising candidate for various biomedical applications. This study focuses on the biosynthesis of silver nanoparticles using phycocyanin, a natural pigment extracted from Arthrospira platensis algae and evaluates their antifungal activity against two pathogenic fungi: Aspergillus fumigatus and Fusarium oxysporum . The synthesis process began with the extraction of phycocyanin from Arthrospira p. microalgae, followed by the reduction of silver ions in a 20 mM silver nitrate solution through interaction with the extracted phycocyanin. The formation of silver nanoparticles was confirmed by observing an absorption peak at 450 nm using UV-Vis spectroscopy, indicating the successful synthesis of nanoparticles. To further characterize the synthesized nanoparticles, advanced techniques such as Fourier Transform Infrared Spectroscopy (FT-IR), Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) were employed. These analyses revealed that the nanoparticles exhibited a size range of 30–110 nm, with an average size of approximately 50 nm. Additionally, the antifungal efficacy of the silver nanoparticles was assessed by measuring the colony size and calculating the percentage of growth inhibition for both A. fumigatus and F. oxysporum . The results demonstrated significant antifungal activity, highlighting the potential of these biosynthesized nanoparticles as effective agents against fungal infections.