Antimicrobial, Antioxidant, and Antiviral Activities of Biosynthesized Silver Nanoparticles by Phycobiliprotein Crude Extract of the Cyanobacteria Spirulina platensis and Nostoc linckia

The present work was designed for the biosynthesis of silver nanoparticles (AgNPs) by Spirulina platensis and Nostoc linckia phycobiliprotein extract and for evaluation of their antimicrobial, antioxidant, and antiviral activities. The biosynthesized AgNPs were characterized by UV-Vis spectroscopy, Fourier transform-infrared spectroscopy, transmission electron microscopy, X-ray diffraction analysis, and Zeta potential analysis. The antimicrobial activity of the biosynthesized AgNPs was tested by the disk diffusion method. The antioxidant activity of the nanoparticles was assessed by using DPPH radical scavenging, total antioxidant capacity, and ferric reducing antioxidant assays. The antiviral activity of AgNPs was also challenged with the hepatitis C virus (HCV). The appearance of the surface plasmon resonance band at 420 nm indicated the biosynthesis of AgNPs. TEM images revealed that AgNPs had a mean average size of 21.211 and 21.052 nm for S. platensis and N. linckia, respectively. XRD analysis confirmed its spherical crystalline shape, and FTIR analysis suggested that proteins were responsible for their capping and stabilization. Zeta potential recorded - 15.902 mV and - 16.811 mV for S. platensis and N. linckia AgNPs, respectively, confirming its stability. AgNPs showed potent antimicrobial activity against some bacterial pathogens and Candida albicans. The antioxidant activity of AgNPs was evident by the use of three antioxidant assays. Significant antiviral activity against HCV (64.976%) was recorded for AgNPs of N. linckia, compared with Ribavirin (66.673%) as a standard drug, while S. platensis AgNPs recorded 48.334%. In conclusion, AgNPs biosynthesized from cyanobacterial phycobiliproteins were stable and showed potent antimicrobial, antioxidant, and antiviral activities.