Silver Micro-Nanoparticle-Based Nanoarchitectures: Synthesis Routes, Biomedical Applications, and Mechanisms of Action

Abstract

Silver has become a potent agent that can be effectively applied in nanostructured nanomaterials with various shapes and sizes against antibacterial applications. Silver nanoparticle (Ag NP) based-antimicrobial agents play a major role in different applications, including biomedical applications, as surface treatment and coatings, in chemical and food industries, and for agricultural productivity. Due to advancements in nanoscience and nanotechnology, different methods have been used to prepare Ag NPs with sizes and shapes reducing toxicity for antibacterial applications. Studies have shown that Ag NPs are largely dependent on basic structural parameters, such as size, shape, and chemical composition, which play a significant role in preparing the appropriate formulation for the desired applications. Therefore, this review focuses on the important parameters that affect the surface interaction/state of Ag NPs and their influence on antimicrobial activities, which are essential for designing future applications. The mode of action of Ag NPs as antibacterial agents will also be discussed.

Keywords: antibacterial; infectious diseases; pathogens; silver nanoparticles.

Figure 1

The number of annual publications on the topic of interest showing exponential growth (created using Scopus database [47]).

Scheme 1

The synthesis scheme of Ag NPs via various methods GO (adapted with permission from reference [67]).

Figure 2

Schematic illustration of the size and shape of Ag/AgCl NPs controlled by (a) the PDDA surfactant, (b) GO sheets, and (c) both PDDA and GO (adapted with permission from reference [63]).

Figure 3

TEM images of Ag NPs: (a) Ag/AgCl/GO and (b–d) Ag/AgCl/rGO synthesized in the presence of GO and PDDA, (e) scanning electron microscope (SEM) images of Ag/AgCl synthesized in the presence of the PDDA surfactant, and (f) TEM image of Ag/AgCl/rGO synthesized without PDDA (adapted with permission from reference [63]).

Figure 4

Photographs of E. coli and S. aureus grown around a series of concentrations of Ag/AgCl/rGO nanomaterials on the plates (adapted with permission from reference [63]).

Figure 5

Growth profile in LB medium with serial concentrations of Ag/AgCl/rGO nanomaterial added to the culture of (a) E. coli and (b) S. aureus. Bacteria time–kill profiles within 2.5 h for (c) E. coli in the presence of 1 or 5 mg L⁻¹ Ag/AgCl/rGO nanomaterial and (d) S. aureus in the presence of 10 or 20 mg L⁻¹ Ag/AgCl/rGO nanomaterial. The bacteria time−kill profiles of E. coli (c) and S. aureus (d) treated with Ag/AgCl/rGO were also performed in a dark environment or with the OH* radical scavenger (adapted with permission from reference [63]).

Figure 6

(a) Growth profiles of wild-type E. coli and (b) of MDR E. coli strains in the presence of control and various concentration of NCN@Ag NPs (adapted with permission from reference [115]).

Figure 7

Digital image of Kappa-Carrageenan/Ag bio-nano composite with the various ratios of Ag-NPs (adapted with permission from reference [61]).

Figure 8

Cytotoxic effect of hydrogel Kappa-Carrageenan/Ag nanocomposites on the growth inhibition of VERO cells (adapted with permission from reference [61]).

Figure 9

Inhibition experiments: images for 355–500 um after silanization and before Ag NP coating (a) and after Ag NP coating (b). Ten millimeter scale bar for both images (adapted with permission from reference [120]).

Figure 10

Percent cell viability loss in HepG2 cell viability (adapted with permission from reference [64]).

Figure 11

ROS fluorescence (a.u) for silver oxide nanoparticles exposed in in vitro HepG2 model (adapted with permission from reference [64]).

Figure 12

(a) The effect of Ag ions on the inactivation of E. coli ATCC8739 in the absence or presence of oxygen. (c) The effect of silver ions on the inactivation of S. aureus ATCC6538. (b,d) The proportion of ROS-mediated inactivation by silver ions at 40 and 60 min (N₀ = 10⁶ CFU/mL, pH 7.1) (adapted with permission from reference [118]).

Figure 13

Antibacterial action of Ag NPs under aerobic and anaerobic atmosphere (adapted with permission from reference [121]).

Figure 14

Summary of the factors affecting Ag NP dissolution and inhibition of growth of bacteria (adapted with permission from reference [5]).