Gold nanoparticles synthesized from soil-derived Streptomyces sp. ASM19: characterization, antimicrobial, anticancer...

Gold nanoparticles (Au) have attracted considerable attention in the field of biomedicine in recent years. The present work was designed to investigate gold nanoparticles obtained using a soil-associated actinomycetes, Streptomyces sp. ASM19. This microorganism was isolated and identified using DNA sequencing. The chemical profile of the Streptomyces sp. ASM19 extract was analyzed using LC-HRES-MS. Streptomyces sp. ASM19 extract was utilized to synthesize actinomycetes-based gold nanoparticles (Ac-AuNPs), which were analyzed using ultraviolet-visible (UV-vis) spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). In addition, the antibacterial, and anti-biofilm, as well as, the anti-proliferative properties of Ac-AuNPs against seven cancer lines were investigated. LC-HRES-MS analysis traced a total of 111 peaks, 14 of them are key peaks belonging to the chemical classes, alkaloids, steroids, and polyketides. Analysis of the synthesized Ac-AuNPs revealed that they exhibited a wine-red color and a plasmon band appeared at 540 nm, confirming the formation of the Ac-AuNPs. Further, FTIR confirmed various functional groups present in Ac-AuNPs. The crude extract of Streptomyces sp. ASM19 demonstrated consistent antibacterial activity in contrast to Ac-AuNPs. The anti-proliferative properties of Ac-AuNPs demonstrated encouraging anticancer properties against SCC9 and SCC25 cell lines with IC₅₀ values of 3.77 and 1.56 μg mL^-1. Furthermore, Ac-AuNPs had total apoptotic percentages of 26.37% (SCC9) and 32.08% (SCC25), which are around 25 times higher than the control (0.95%). Additionally, it caused a notable G2/M phase cell-cycle arrest. On the other hand, molecular docking study carried out for the annotated compounds; tomaymycin (8) and nocapyrone P (5), showed considerable binding affinities compared to the co-crystallized inhibitor (fisetin) against the cyclin-dependent kinase 6 active site. Overall, the present study could be useful for nano drug delivery and may be applied for clinical studies in the future.