Isolation, biosynthesis and antimicrobial activity of gold nanoparticles produced with extracts of Anabaena spiroides

Multidrug-resistant (MDR) pathogenic bacteria have become dangerous in bringing sporadic outbreaks in public health and nosocomial spreads from the addition of antibacterials/antibiotics continually. Obviously, the pharmacy world is in search of antibacterials that would be invincible by the evolved bacteria. Green synthesis of gold-nanoparticles (AuNps) was focused on the use of aqueous chloroauric acid (HAuCl 4 ) and cell-free aqueous extract of the N 2 -fixing cyanobacterium (blue-green alga) Anabaena spiroides collected from a brackish-water, Bay of Bengal at Puri, Odisha; green-synthesized AuNps could be used as antibacterials against MDR bacteria. The synthesized AuNps were subjected to the following characterizations, UV–Vis spectrophotometry, SEM–EDX, XRD and ART-FTIR analysis. An absorption peak at 538 nm by UV–Vis spectrophotometry and the FTIR analysis confirmed the presence of AuNps. A. spiroides -AuNps were monitored for antibacterial activities against MDR pathogenic bacterial strains isolated from clinical samples, namely, Klebsiella oxytoca, MRSA and Streptococcus pyogenes, in vitro ; the individual antibiograms of those bacteria were known. The recorded MIC dose values were 25, 20 and 30 mg A. spiroides -AuNps ( As -AuNps) against K. oxytoca , MRSA and S. pyogenes, in vitro , respectively. Thus, As -AuNps bear promises as possible antibacterials, in future. Graphic abstract