Present study involves the simple, rapid, non-toxic and in vitro method of extracellular silver nanoparticles synthesis using Entomopathogenic fungus (Beauveria bassiana). The development of silver nanoparticle in fungal supernatant was confirmed by the absorbance peak at 450 nm in UV-Vis spectrophotometer. Further, presence of AgNPs and its crystal lattice was confirmed by EDS and XRD, respectively. TEM micrograph confirmed the presence of differently shaped (triangular, circular, hexagonal) nanoparticles with size ranging from 10 to 50 nm. Variable shape and size of fungal assisted AgNps was also confirmed in SEM study. The optimal pH and temperature for biosynthesis of nanoparticles was found to be 6.0 and 25 °C, respectively. The continuous effects of AgNPs against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus in time dependent manner was confirmed in growth kinetic studies. During 36 h of growth study, maximum reduction in O.D 560 was found in E. coli (67.2%) followed by P. aeruginosa (63.3%) and S. aureus (56.8%) at 30 °C. The MIC values of fungal assisted AgNPs against E. coli, P. aeruginosa and S. aureus was found to be 2.5, 3 and 4.5 ppm, respectively. The MIC values of Ciprofloxacin was observed to be 0.5, 0.5 and 0.7 ppm, whereas MICs of AgNPs + Ciprofloxacin showed 0.4, 0.4, 0.5 ppm against E. coli, P. aeruginosa and S. aureus, respectively, clearly highlighting the synergistic effect of AgNPs in combination with Ciprofloxacin. In the view of challenges for developing antimicrobial nanoparticles of variable shape and size by various other methods, tuning nanoparticles synthesis via fungi can be a wonderful approach to resolve existing hurdles.

Silver nanoparticle synthesis of the leaf extract Tagetes erecta L. enriched with ascorbic acid and polyphenols has been investigated. The color of the golden yellow extract has changed to pinkish-brown due to the reduction of Ag+ to the colloidal solution of AgNPs and a sharp absorption peak at 420 nm under the UV-Vis spectrophotometer. In addition, the Fourier Transfer Infrared Spectroscopy (FTIR) estimation was completed in order to recognize and identify the biomolecules present in the extract acting as a reducing and capping agent for the AgNPs. The X-ray diffraction (XRD) peaks at (111), (201), (220), and (311) confirm the presence of monoclinic crystals in the solution. The morphology and size of the particles were provided by transmission electron microscopy (TEM) images of AgNPs. At a scale of 100 nm, synthesized AgNPs were predominantly spherical with a size range of 7-35 nm. In comparison to 7.39 mg/100 g in AgNPs, aqueous leaf extract was 55.14 mg/100 g higher in ascorbic acid. The phenolic and flavonoid content of extract was 52.54 ± 2.15  mg (GAE/100 g) and 15.43 ± 0.34  mg (QE/mL), and the colloidal AgNP solution was 21.45 ± 1.15  mg (GAE/100 g) and 8.05 ± 2.42  mg (QE/mL), respectively. Phenolic and flavonoid contents play a major role as a reducing agent and reduce the precursor AgNO3 into AgNPs. The DPPH scavenging assay also assessed the antioxidant properties of extract and its derived AgNPs. As compared antioxidant value to aqueous leaf extract (mg/mL), higher percentage inhibition (PI) was found in AgNPs and free-radical scavenging activity of extract and AgNPs were directly linked to their concentrations. Results of this research have discovered a higher potential for free-radical scavenging AgNPs and will help to develop new and more potent antioxidants for the treatment of different diseases caused by oxidative stress; the higher antioxidant properties bearing AgNPs might be used.

For nearly a decade, silver nanoparticles (AgNPs) have been the most prevalent commercial nanomaterials products widely used in different biomedical applications due to their broad-spectrum antimicrobial activity.

Spinacia oleracea (spinach) and Musa acuminata (banana) were chosen for the study, and aqueous extracts of spinach leaf extract (SLE) and banana peel extract (BPE) were prepared for the synthesis of iron nanoparticles (FeNPs), and their antibacterial potential against pathogenic bacteria Bacillus subtilis (MTTC 1133) and Escherichia coli (MTTC 62) was evaluated. In 10 minutes at 60°C, the color of the mixture (FeCl3+SLE) changed from light green to dark blackish-brown, and the color of the mix (FeCl3+BPE) changed from transparent yellow to dark black, confirming the synthesis of FeNPs from SLE and BPE, respectively. The UV-Vis spectra of spinach- and banana-derived FeNPs revealed two peaks ranging from 240 to 430 nm and multiple peaks at 240, 270, and 395 nm, respectively. FTIR spectroscopy was used to show different functional groups on BPE and SLE, and their role in FeNP synthesis was predicted. TEM micrographs showed that the particles were in nanoscale, ranging in size from 20 to 50 nm for BPE-derived FeNPs and 10 to 70 nm for SLE-derived FeNPs. The FeNP (BPE and SLE) XRD analysis revealed amorphism, with a weak iron characteristic peak, indicating noncrystallinity. The antibacterial potential of BPE- and SLE-FeNPs was investigated, and inhibition zones (mm) against B. subtilis ( 22.70 ± 0.4 ) and E. coli ( 20.45 ± 1.66 ) were observed, as well as SLE-FeNPs against B. subtilis ( 23.56 ± 1.00 ) and E. coli ( 20.33 ± 0.58 ). There were no significant differences in antibacterial activities between BPE-FeNPs and SLE-FeNPs. Positive controls were tetracycline and gentamicin, both standard antibiotics, at 5 μg/disk. SLE- and BPE-derived green FeNPs were also analysed in vivo of D. melanogaster life history traits, i.e., fecundity, hatchability, viability, and duration of development for toxicity evaluation. SLE- and BPE-derived green FeNPs at a concentration of 10 mg/L were fed flies compared to normal diet-fed flies (control sample), and no significant differences were observed between them. The findings suggest that FeNPs have a high antibacterial potential and could be used as antibacterial agents against pathogenic bacteria while being nontoxic in nature.