Characterization and Antimicrobial Properties of Silver and Silver Oxide Nanoparticles Synthesized by Cell-Free Extract of a Mangrove-Associated Pseudomonas aeruginosa M6 Using Two Different Thermal Treatments

Abstract

Synthesis of silver nanoparticles by cell-free extract (CFE) of Pseudomonas aeruginosa M6 isolated from a mangrove ecosystem was demonstrated using two physical methods, namely, boiling (conventional thermal treatment (CTT)) and microwave treatment (MWT) at pH 9. X-ray diffraction (XRD) analysis revealed the presence of smaller (10.4 nm), pure silver nanoparticles synthesized via CTT (C-NPs) and larger silver oxide nanoparticles in majority with negligible concentration of pure silver particles by MWT. Transmission electron microscopy (TEM) analysis showed that C-NPs are spherical in shape. Atomic force microscopy (AFM) analysis also confirmed the presence of large-sized, aggregated nanoparticles synthesized via MWT (M-NPs). Electrophoresis indicated the size and charge-based mobility in agarose gel (0.4%), wherein the C-NPs moved faster than M-NPs, because of their relatively smaller size. The zeta potential value of C-NPs and M-NPs was found to be −30.1 mV and −23.1 mV, respectively. Fourier transform infrared (FT-IR) results revealed that both C-NPs and M-NPs were capped with proteins, but with different conformations. Furthermore, TEM analysis of bacterial cells exposed to aqueous silver nitrate showed the presence of spherical silver nanoparticles accumulated in periplasmic space, indicating the possible involvement of periplasmic nitrate reductase in this process. In addition, both C-NPs and M-NPs have also shown good antibacterial and anticandidal activities. Thus, marine Pseudomonas aeruginosa M6 can be a potential source for the synthesis of silver nanoparticles.

Green Simplistic Biosynthesis of Anti-Bacterial Silver Nanoparticles Using Annona Squamosa Leaf Extract

“…Earlier, we obtain similar kind of results in the biosynthesis of silver nanoparticles using seaweed, Ulva lactuca [18]. Altogether, a small peak at 38.14 indicates the formation of pure silver [19]. A few negligible spurious diffraction arises signifying the presence of impurities in the sample.…”

Antimicrobial Activity of Biosynthesized Silver Nanoparticles against E. coli and B. subtilis

“…In literature, different sizes of biosynthesized AgNPs were reported [6,18,23]. Averages of 20-50 nm AgNPs were produced by using leaf extract of Acalypha hispida [18].…”

“…Averages of 20-50 nm AgNPs were produced by using leaf extract of Acalypha hispida [18]. Other sizes of AgNPs were recorded, For example, 50-100 nm of AgNPs were recorded to be produced by bacteria whereas AgNPs sizes of 5-55 nm were recorded to be produced by nitrate reductase extracted from the leaf of Dalbergia sisso [6,23]. The production of different sizes of AgNPs is key factors in deciding the application.…”

Role of Cloud Point of the Capping Agent (Nonionic Surfactant, Triton X-100) on the Synthesis of Silver Nanoparticles

“…Because of the feasibility in manipulating the basic structure and composition of the NPs, the NPs have obtained strong scientific scope for the application of nanotechnology in multiple fields. [1] A growing number of manufactured nanomaterials have raised concerns regarding the impact of these materials and the products. [1,2] Since the ancient times, silver, a noble metal has already been known as a very effective antimicrobial agent.…”

“…[1] A growing number of manufactured nanomaterials have raised concerns regarding the impact of these materials and the products. [1,2] Since the ancient times, silver, a noble metal has already been known as a very effective antimicrobial agent. Silver nanoparticles (AgNPs) are exceedingly used as antibacterial, antiviral and antifungal agents worldwide.…”