Table 3 Effects of negatively charge ligand-conjugated metal nanoclusters (NCs) towards gram-positive and gram-negative bacteria

Gold NCs (AuNCs)-MBA

Staphylococcus aureus

Escherichia coli

− 32.2 ± 3.4 mV

Au₂₅NCs-MBA killed both gram-positive and gram-negative bacteria

Reactive oxygen species (ROS) formation increased when there was a metabolic imbalance that led to the overproduction of pro-oxidative enzymes and suppression of antioxidative enzymes

[61]

Au_xAg_25-x(MHA)₁₈ NCs

S. aureus

E. coli

− 36 to − 32 mV

The variation of nanoclusters showed a U-shaped antimicrobial trend for both gram-positive and gram-negative bacteria; Au-rich NCs had a decreased antimicrobial ability, while Ag-rich NCs had an increased antimicrobial ability

ROS generation, inducement of oxidative stress, regular metabolism interference

[124]

Au₂₅MHA₁₈NCs

Au₂₅Cys₁₈NCs

Au₂₅Cystm_xMHA_18-xNCs

Au₂₅MetH_xMHA_18-xNCs

Au₂₅MBA₁₈NCs

S. aureus

E. coli

− 20.5 ± 4.1 to

− 37.4 ± 2.5 mV

By adjusting both the type and ratio of surface ligands on AuNCs, negatively charged AuNCs produced more ROS, resulting in greater gram-positive and gram-negative bacterial killing efficiencies

Cell uptake, NC internalization, ROS generation

[111]

(Au₂₅Cystm_1-4MHA_17-14) on Holmium ions (Ho)-graphene oxide (GO) nanosheets

S. aureus

E. coli

− 37.6 mV

Ho-GO-AuNCs killed both gram-positive and gram-negative bacteria

Cell uptake, NC internalization, ROS generation

[125]

Ag-GSH-NCs encapsulated with liposomes

S. aureus

B. subtilis

E. coli

Pseudomonas aeruginosa

− 29.3 ± 0.8 mV

Ag-GSH-NCs killed both gram-positive and gram-negative bacteria

ROS generation

[126]

AuNCs-MHA

Cloistridioides difficile

–

Negative

(not mentioned)

AuNCs-MHA killed C. difficile without causing a significant toxic effect on human cells

Metabolic imbalance, ROS generation

[127]

AuNCs-MHA

–

Shigella (Sf301, R2448 & RII-1)

Negative

(not mentioned)

AuNCs-MHA represented a good potential alternative to antibiotics to treat Shigella infections

Cell membrane damage, ROS generation

[128]

GSH-AuNCs

–

Acetobacter aceti

Negative

(not mentioned)

Antibacterial activity increased with the concentration of GSH-AuNCs, as demonstrated by bacterial growth curves

ROS generation

[129]

Negatively charged ligand-conjugated metal NCs which showed better antibacterial effects against gram-negative bacteria than gram-positive bacteria

AuNCs-MHA

S. aureus

B. subtilis

E. coli

A. baumannii

Negative

(not mentioned)

The antibacterial effect of AuNCs-MHA worked better against gram-negative bacteria than gram-positive ones. MIC levels for E. coli and A. baumannii were 50 and 200 µM while for S. aureus and B. subtilis, both required > 200 µM

Interactions with the phospholipid bilayer, cytosolic protein binding, ROS generation

[76]

Luminescent copper NCs (CuNCs)-doped hydroxyapatite nanoparticles (HAP NPs)

S. aureus (MTCC 96)

B. subtilis (MTCC 1305)

E. coli (DH5α)

P. aeruginosa (MTCC 2488)

− 3.14 ± 0.17 mV

It was discovered that the kanamycin-loaded doped HAP NPs were more efficient against gram-negative bacteria than gram-positive bacteria

Formation of hydroxyl radicals, depletion of NADH, cell damage

[100]

Dihydrolipoic acid-stabilized dual-functional silver NCs (DHLA-AgNCs)

S. aureus

E. coli

− 28.8 mV

Results showed that DHLA-AgNCs exhibited excellent antibacterial activities against gram-negative but had no apparent antibacterial activity against gram-positive bacteria

Cell membrane damage

[130]

Negatively charged ligand-conjugated metal NCs which showed better antibacterial effects against gram-positive bacteria than gram-negative bacteria

AuNCs-MBA

S. aureus

E. coli

− 36 + 2.3 mV

AuNCs-MBA generated higher ROS levels for gram-positive bacteria than gram-negative bacteria

Physical absorption into the cell membrane, metabolic imbalance, ROS generation

[131]

Au₂₅(MBA)₁₈ NCs on MXene nanosheets

S. aureus

E. coli

− 16.8 mV

Both gram-positive and gram-negative bacteria were eventually killed due to synergistic physical (through MXene) and chemical (via MXene and AuNCs) antibacterial processes; however, the outcome was marginally more beneficial for gram-positive bacteria

Cell membrane damage, ROS generation

[132]

Thiol-terminated phosphorylcholine (PC-SH)-protected silver NCs (PC-AgNCs)

S. aureus

E. coli

Negative

(not mentioned)

PC-AgNCs worked against both gram-positive and -negative bacteria, but were better against gram-positive bacteria

Cell membrane damage, ROS generation

[133]

Photobactericidal polymer containing crystal violet (CV) and thiolated gold NCs (Au₂₅(Cys)₁₈)

S. aureus

E. coli

− 31.8 mV

By white light, the materials worked in both gram-positive and gram-negative bacteria but were better for gram-positive bacteria

Promotion of hydrogen peroxide (H₂O₂) and ROS generation

[134]