This study investigated the green biosynthesis of gold (Au) and silver-gold alloy (Ag-Au) nanoparticles using cell-free extract of Bacillus safensis LAU 13 strain (GenBank accession No: KJ461434). The biosynthesized AuNPs and Ag-AuNPs were characterized using UV-Vis spectroscopy, Fourier-transform infrared spectroscopy, and transmission electron microscopy. Evaluation of the antifungal activities, degradation of malachite green, anti-coagulation of blood, and thrombolysis of human blood clot by the biosynthesized nanoparticles were investigated. The AuNPs and Ag-AuNPs had maximum absorbance at 561 and 545 nm, respectively. The FTIR peaks at 3318, 2378, 2114, 1998, 1636, 1287, 446, 421 cm for AuNPs; and 3310, 2345, 2203, 2033, 1636, 1273, 502, 453, 424 cm for Ag-AuNPs indicated that proteins were the capping and stabilization molecules in the biosynthesized nanoparticles. The particles were fairly spherical in shape with size of 10-45 nm for AuNPs and 13-80 nm for Ag-AuNPs. Moreover, energy dispersive X-ray analysis of AuNPs revealed gold as the most prominent metal in the AuNPs solution, while silver and gold were the most prominent in the case of Ag-AuNPs. Selected area electron diffraction showed the biosynthesized nanoparticles as crystal structures with ring shape pattern. AuNPs and Ag-AuNPs displayed growth inhibitions of 66.67-90.78% against strains of Aspergillus fumigatus and A. niger at concentration of 200 μg/ml , and remarkable degradation (> 90%) of malachite green after 48 h. Furthermore, the nanoparticles prevented coagulation of blood, and also completely dissolved blood clots, indicating the biomedical potential of AuNPs and Ag-AuNPs in the management of blood coagulation disorders. This is the first report of the synthesis of AuNPs and Ag-AuNPs using a strain of B. safensis for biomedical and catalytic applications.

Phytosynthesis of silver nanoparticles (AgNPs) using leaf extract of Petiveria alliacea (PA) was the focus of this research work. The PA-AgNPs were characterized by UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) study. Studies were made on the AgNPs for antibacterial, antifungal, anticoagulant, free-radical scavenging, and hydrogen peroxide scavenging activities. The crystalline PA-AgNPs were monodispersed, with a size range of 16.70-33.74 nm and maximum absorption at 410 nm. FTIR analysis displayed prominent peaks at 3430.6, 1711.8, and 1165.9/cm, which showed the existence of phenolic compounds and proteins in the synthesis of AgNPs. PA-AgNPs was active against Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus, with 100% inhibition. The PA-AgNPs also displayed good antifungal properties, as the concentrations of 100 and 150 µg/mL had 100% inhibition toward Aspergillus fumigatus and Aspergillus flavus. However, there was 66.67% inhibition of Aspergillus niger. It scavenged both DPPH and HO by 70.69 and 89.02%, respectively. PA-AgNPs also prevented the coagulation of human blood. This study, being the first of its kind to use the leaf extract of PA for the synthesis of AgNPs has shown that PA-AgNPs can find biomedical applications.

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Aqueous leaf extract of Hyptis suaveolens was investigated to synthesize silver nanoparticles (Hs-AgNPs). Biomolecules such as phenolics, proteins, carbohydrates and esters facilitated bioformation of Hs-AgNPs with ƛmax at 420 nm. The nearly spherical Hs-AgNPs were polydispersed and sized 29.19-52.27 nm with yield of 85.8 %. Hs-AgNPs showed potent inhibition of 75.22-100 % against multidrug resistant bacteria, and fungal growth inhibition of 73.33-100 %. Hs-AgNPs scavenged DPPH and H2O2 by 77.75-83.19, and 54.21-70.11 % respectively. It also effectively inhibited coagulation of blood. The study established the nanobiotechnological importance of H. suaveolens, with bioformation of AgNPs that have potent activities for environmental and biomedical applications.