Table 1.
Structure and mode of action of antimicrobial peptides and proteins used to create conjugates with silver nanoparticles (AgNPs).
| Conjugate | Antimicrobial peptide or protein introduced into the coating of the nanoparticle | ||
|---|---|---|---|
| Type, name and source | Size and structure | Mode of antimicrobial action | |
| AgNP-PG1 | AMP Protegrin-1 (PG-1) porcine |
18 residues (2.2 kDa) β-hairpin 2 S-S bonds; cationic (+6)a |
Permeabilizes membranes (possibly forming toroidal pores; Sokolov et al., 1999; Lazaridis et al., 2013) |
| AgNP-Ind | AMP Indolicidin bovine |
13 residues (1.9 kDa) linear Trp-rich; cationic (+3)a |
Self-translocates into the cytoplasm. Acts as carrier for organic anions without forming pores (Rokitskaya et al., 2011), interferes with nucleic acids synthesis by directly binding to DNA abasic sites and inhibiting topoisomerase I (Marchand et al., 2006) |
| AgNP-Prot | AP Protamine salmon |
32 residues (4.2 kDa) disordered Arg-rich, cationic (+2)a |
Does not alter the overall permeability of bacterial cytoplasmic membrane or lyse cells, but affects energy transduction and amino-acid uptake, ultimately inhibiting protein synthesis (Aspedon and Groisman, 1996) |
| AgNP-His | AP Histones calf thymus |
~ 100–220 residues (~ 11–21 kDa) globule with flexible tails Lys/Arg-rich, cationic ~ (+1.2–2.6) every 10 res.a |
Most histones disrupt bacterial membranes. Lys-rich histone H2B can penetrate into the cells without affecting membrane integrity and bind to DNA. Fragmentation by bacterial proteases promotes activity against E. coli, but not S. aureus (Tagai et al., 2011; Morita et al., 2013; Hoeksema et al., 2016). |
| AgNP-Lyz | AP Lysozyme hen egg-white |
129 residues (14.3 kDa) globular cationic (~ +0.6 every 10 res.)a |
Targets the bacterial cell wall by hydrolyzing β1-4-glycosidic linkages between N-acetylmuramic acid and N-acetyl-β-glucosamine residues in peptidoglycan. An additional non-enzymatic AMP-like mechanism is proposed (membrane lysis) as catalytically inactive variants retain some antimicrobial efficacy (Laible and Germaine, 1985; Ibrahim et al., 2001; Wiesner and Vilcinskas, 2010) |
a
Charge was calculated as the number of arginine and lysine residues minus the number of aspartic and glutamic acid residues (C-amidation was not taken into account).