Gold-Based Nanostructures for Antibacterial Application

Abstract

Bacterial infections have become a fatal threat because of the abuse of antibiotics in the world. Various gold (Au)-based nanostructures have been extensively explored as antibacterial agents to combat bacterial infections based on their remarkable chemical and physical characteristics. Many Au-based nanostructures have been designed and their antibacterial activities and mechanisms have been further examined and demonstrated. In this review, we collected and summarized current developments of antibacterial agents of Au-based nanostructures, including Au nanoparticles (AuNPs), Au nanoclusters (AuNCs), Au nanorods (AuNRs), Au nanobipyramids (AuNBPs), and Au nanostars (AuNSs) according to their shapes, sizes, and surface modifications. The rational designs and antibacterial mechanisms of these Au-based nanostructures are further discussed. With the developments of Au-based nanostructures as novel antibacterial agents, we also provide perspectives, challenges, and opportunities for future practical clinical applications.

Keywords: antibacterial mechanism; bacterial infection; gold nanobipyramids; gold nanoclusters; gold nanoparticles; gold nanorods; gold nanostars.

Figure 1

(a) Schematic representation of cefotaxime (CTX)-loaded gold nanoparticle (C-AuNP) synthesis and CTX and C-AuNP minimal inhibitory concentrations for (b) Escherichia coli, (c) Pseudomonas aeruginosa, (d) Klebsiella oxytoca, and (e) Staphylococcus aureus. Reproduced from ref. [51].

Figure 2

Ciprofloxacin: gold nanoparticle (CIP:AuNP) synthesis schematic and representation of the antibacterial pathway using sonodynamic antimicrobial chemotherapy (SACT). Reproduced from ref. [57].

Figure 3

Epigallocatechin gallate (EGCG) added to hydrogels modified with gold nanoparticles (AuNPs; E-Au@H) synthesis schematic and representation of the antibacterial pathway. Reproduced from ref. [64].

Figure 4

Sulfomethoxazole (SMX)-conjugated magnetic and gold nanoparticle (AuNP) synthesis and antibacterial studies. Reproduced with permission from ref. [69]. Copyright 2022 Elsevier.

Figure 5

The synthesis approach of thioproline (T) (Boc-protected (B))-gold nanoparticles (AuNPs) to modify their antibacterial activity as schematically depicted. Reproduced with permission from ref. [75]. Copyright 2022 Royal Society of Chemistry.

Figure 6

(a) Stages of antibacterial mechanism of gold nanoclusters (AuNCs). Reproduced with permission from ref. [84]. Copyright 2022 American Chemical Society. (b) Illustration of bacterial eradication by AuNCs. Reproduced with permission from ref. [88]. Copyright Elsevier 2021. (c) Interaction analysis of bacteria and AuNCs at different time points. Reproduced with permission from ref. [91]. Copyright 2022 American Chemical Society.

Figure 7

Antibacterial performance of gold nanoclusters (AuNCs) with the N-heterocyclic carbene ligand. (a) Photographs of agar plates and (b) colony forming unit (CFU) reduction rates of S. aureus, E. coli, and C. albicans incubated with AuNCB50 at various concentrations in the dark for 10 min. (c) CFU reduction rates of S. aureus, E. coli, and C. albicans incubated with AuNCs at different ligand ratios. (d) Live/dead staining of S. aureus before and after incubation with AuNC-B50 (20 µg/mL) for 30 min. Reproduced with permission from ref. [86]. Copyright 2022 Elsevier.

Figure 8

Quaternary ammonium (QA)-gold nanoclusters (AuNCs) conjugated with indocyanine green (ICG) revealed triple weapons, including direct killing, photodynamic therapy (PDT), and photothermal therapy (PTT) for methicillin-resistant Staphylococcus aureus (MRSA) eradication under near-infrared (NIR) irradiation. Reproduced with permission from ref. [92]. Copyright 2022 Elsevier.

Figure 9

Excellent ability of gold nanoclusters (AuNCs) to fix problems due to oral biofilms. Reproduced from ref. [96].

Figure 10

Illustration of the preparation of molybdenum-disulfide-conjugated gold nanorod (MoS₂@AuNR) nanocomposites and their antibacterial application based on photothermal therapy (PTT) and photodynamic therapy (PDT). Reproduced from ref. [103].

Figure 11

(a) Schematic illustration of gold nanobipyramids (AuNBPs) with the (111) plane for water desorption under near-infrared (NIR) laser irradiation. Reproduced with permission from ref. [105]. Copyright 2021 Elsevier. (b) Evaluation of in vivo antibacterial activity and antibacterial mechanisms of AuNBPs functionalized with chiral glutamic acid (D/L-Glu-AuNBPs). Reproduced with permission from ref. [106]. Copyright 2020 Elsevier.

Figure 12

Schematic Illustration of vancomycin-coated gold nanostars (AuNSs@Van) for targeting and killing methicillin-resistant Staphylococcus aureus (MRSA) under near-infrared (NIR) laser irradiation. Reproduced with permission from ref. [109]. Copyright 2019 American Chemical Society.