Pseudomonas indica-Mediated Silver Nanoparticles: Antifungal and Antioxidant Biogenic Tool for Suppressing Mucormycosis Fungi

Abstract

Mucormycosis is considered one of the most dangerous invasive fungal diseases. In this study, a facile, green and eco-friendly method was used to biosynthesize silver nanoparticles (AgNPs) using Pseudomonas indica S. Azhar, to combat fungi causing mucormycosis. The biosynthesis of AgNPs was validated by a progressive shift in the color of P. indica filtrate from colorless to brown, as well as the identification of a distinctive absorption peak at 420 nm using UV-vis spectroscopy. Fourier-transform infrared spectroscopy (FTIR) results indicated the existence of bioactive chemicals that are responsible for AgNP production. AgNPs with particle sizes ranging from 2.4 to 53.5 nm were discovered using transmission electron microscopy (TEM). Pattern peaks corresponding to the 111, 200, 220, 311, and 222 planes, which corresponded to face-centered cubic forms of metallic silver, were also discovered using X-ray diffraction (XRD). Moreover, antifungal activity measurements of biosynthesized AgNPs against Rhizopus Microsporus, Mucor racemosus, and Syncephalastrum racemosum were carried out. Results of antifungal activity analysis revealed that the biosynthesized AgNPs exhibited outstanding antifungal activity against all tested fungi at a concentration of 400 µg/mL, where minimum inhibitory concentrations (MIC) were 50, 50, and 100 µg/mL toward R. microsporus, S. racemosum, and M. racemosus respectively. In addition, the biosynthesized AgNPs revealed antioxidant activity, where IC₅₀ was 31 µg/mL when compared to ascorbic acid (0.79 µg/mL). Furthermore, the biosynthesized AgNPs showed no cytotoxicity on the Vero normal cell line. In conclusion, the biosynthesized AgNPs in this study can be used as effective antifungals with safe use, particularly for fungi causing mucormycosis.

Keywords: antifungal activity; antioxidant activity; green biosynthesis; mucormycosis; silver nanoparticles.

Figure 1

Process for the biosynthesis of AgNPs.

Figure 2

A neighbor-joining (NJ) tree based on 16S rRNA gene sequence analysis was used to show the phylogenetic relationships of the isolated strain S. Azhar with comparable type strains.

Figure 3

UV–Vis spectrophotometer (A) and FT-IR spectra (B) of AgNPs synthesized by P. indica S. Azhar.

Figure 4

TEM image of AgNPs synthesized by of P. indica S. Azhar.

Figure 5

XRD pattern (A) and SAED pattern (B) of biosynthesized AgNPs.

Figure 6

Antifungal activity of AgNPs at 400 µg/Ml using the agar well diffusion method (A) and the MIC of AgNPs using the broth microdilution method (B) toward R. microsporus, S. racemosum, and M. racemosus.

Figure 7

Antioxidant activity of AgNPs at different concentrations using DPPH method.

Figure 8

Cytotoxicity of AgNPs on Vero cell line.