A review of microbes mediated biosynthesis of silver nanoparticles and their enhanced antimicrobial activities

Abstract

In recent decades, biosynthesis of metal and (or) metal oxide nanoparticles using microbes is accepted as one of the most sustainable, cost-effective, robust, and green processes as it does not encompass the usage of largely hazardous chemicals. Accordingly, numerous simple, inexpensive, and environmentally friendly approaches for the biosynthesis of silver nanoparticles (AgNPs) were reported using microbes avoiding conventional (chemical) methods. This comprehensive review detailed an advance made in recent years in the microbes-mediated biosynthesis of AgNPs and evaluation of their antimicrobial activities covering the literature from 2015-till date. It also aimed at elaborating the possible effect of the different phytochemicals, their concentrations, extraction temperature, extraction solvent, pH, reaction time, reaction temperature, and concentration of precursor on the shape, size, and stability of the synthesized AgNPs. In addition, while trying to understand the antimicrobial activities against targeted pathogenic microbes the probable mechanism of the interaction of produced AgNPs with the cell wall of targeted microbes that led to the cell's reputed and death have also been detailed. Lastly, this review detailed the shape and size-dependent antimicrobial activities of the microbes-mediated AgNPs and their enhanced antimicrobial activities by synergetic interaction with known commercially available antibiotic drugs.

Keywords: Antimicrobial activities; Extracellular; Green synthesis; Intracellular; Microbes-assisted synthesis; Silver nanoparticles.

Graphical abstract

Fig. 1

Research papers published annually for the biosynthesis of silver nanoparticles between 2004 and 2022 (data gathered from the Scopus Database).

Fig. 2

Different methods for the synthesis of nanoparticles. Reproduced with permission from Ref. [3], Copyright 2016, Elsevier.

Fig. 3

Biological synthesis of NPs and their wide applications in different fields. Reproduced with permission from Ref. [16], Copyright 2016, Elsevier.

Fig. 4

Probable reaction pathways of green synthesis of silver nanoparticles using mesophytes. Reproduced with permission from Ref. [22], Copyright 2009, Elsevier.

Fig. 5

The interaction of AgNPs with Gram-positive and Gram-negative bacterial cell walls is depicted schematically. The positively charged/less negatively charged AgNPs interact electrostatically with the negatively charged bacterial cell wall/membrane and disrupt it. Reproduced with permission from Ref. [30], Copyright 2022, American Chemical chemSociety.

Fig. 6

Plausible mechanism of antimicrobial activity of AgNPs.

Fig. 7

FE-SEM analysis of bacteria treated and untreated with AgNPs: morphology of B. cereus, S. aureus, E. coli, and P. aeruginosa (a–d); bacterial cells treated with AgNPs showed membrane damage after 60 min of treatment (e–h). Reproduced from Ref. [55], (Creative Commons CC-BY–NC–ND), Copyright 2017, Elsevier.

Fig. 8

(a) Typical transmission electron micrograph of sphere-shaped AgNPs. Inset showing a single nanoparticle SAED pattern. Particle size distribution histogram of silver nanoparticles as determined using (b) TEM and (c) DLS measurements, reproduced from Ref. [65] (Creative Common Attribution License) Copyright 2015, Public Libra of Science.

Fig. 9

Antibacterial and antifungal activities of G. mangiferae mediated AgNPs. Reproduced with permission from Ref. [68], Copyright 2015, Elsevier.

Fig. 10

Green synthesis of AgNPs and its antibacterial activity are shown schematically, reproduced from Ref. [82] (Creative Common Attribution International License) Copyright 2020, Springer. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 11

MIC of synthesized AgNPs antibacterial activity against (a) E. coli (b) P. aeruginosa (c) K. pneumonia (d) V. cholera (e) S. aureus (f) B. subtilis (g) S. flexneri (h) S. typhi, where inside the figures (A) AgNO₃ (B) algal extracts, (C) chloramphenicol, (D) distilled water, (E) AgNPs. Reproduced from Ref. [106] (Open Access), Copyright 2020, John Wiley & Sons Inc.

Fig. 12

Live/Dead analysis of effective activity of AgNPs on bacterial pathogens control – (a) S. aureus, (b) B. subtilis, (c) E. coli, Experimental – (d) S. aureus, (e) B. subtilis, (f) E. coli. Reproduced from Ref. [119], (Open Access), Copyright 2017, Wiley.

Fig. 13

The main effects of the process variables on the biosynthesis of AgNPs using the supernatant of L. adecarboxylata THHM according to the Plackett–Burman experimental results. Reproduced from Ref. [134], (Creative Common Attribution 4.0 International License) Copyright 2022, Springer.

Fig. 14

Zeta potential of the biosynthesized AgNPs. Reproduced from Ref. [152], (Creative Common CC BY License), Copyright 2018, MDPI.

Fig. 15

UV–vis spectra of B. indica DC1 culture supernatant after treatment with (1 mM) AgNO₃ (a). Anisotropic AgNPs produced by B. indica DC1, 100, and 200 nm in a TEM image (b). Reproduced from Ref. [157] (Creative Common Attribution License), Copyright 2015, Hindawi.

Fig. 16

Zeta Potential (mV) of P. hornemannii mediated AgNPs. Reproduced with permission from Ref. [90], Copyright 2019, Elsevier.