Membrane interactions and antimicrobial effects of layered double hydroxide nanoparticles

Abstract

Membrane interactions are critical for the successful use of inorganic nanoparticles as antimicrobial agents and as carriers of, or co-actives with, antimicrobial peptides (AMPs). In order to contribute to an increased understanding of these, we here investigate effects of particle size (42-208 nm) on layered double hydroxide (LDH) interactions with both bacteria-mimicking and mammalian-mimicking lipid membranes. LDH binding to bacteria-mimicking membranes, extraction of anionic lipids, as well as resulting membrane destabilization, was found to increase with decreasing particle size, also translating into size-dependent synergistic effects with the antimicrobial peptide LL-37. Due to strong interactions with anionic lipopolysaccharide and peptidoglycan layers, direct membrane disruption of both Gram-negative and Gram-positive bacteria is suppressed. However, LDH nanoparticles cause size-dependent charge reversal and resulting flocculation of both liposomes and bacteria, which may provide a mechanism for bacterial confinement or clearance. Taken together, these findings demonstrate a set of previously unknown behaviors, including synergistic membrane destabilization and dual confinement/killing of bacteria through combined LDH/AMP exposure, of potential therapeutic interest.

Oxidation of Polyunsaturated Lipid Membranes by Photocatalytic Titanium Dioxide Nanoparticles: Role of pH and Salinity

“…For instance, a range of inorganic nanomaterials, including metal nanoparticles, metal oxides, quantum dots, graphene, fullerene, and carbon nanotubes, are known to display toxicity against cancer cells − or potent antimicrobial effects. , Nanomaterials may induce such effects by several different mechanisms. For example, depending on the nanoparticle size, hydrophobicity, and charge, nanoparticles may bind to, insert into, and destabilize bacterial and cell membranes. − Furthermore, some nanoparticles may be excited by light ( e.g ., Au nanoparticles) or oscillating magnetic fields ( e.g ., iron oxide nanoparticles), resulting in localized heating and cell lysis. Light may also trigger the generation of reactive oxygen species (ROS), able to oxidize membrane lipids or proteins.…”

Interaction of Laponite with Membrane Components—Consequences for Bacterial Aggregation and Infection Confinement

“…As a result of the negative ζ potential of bare Laponite particles, they do not bind to strongly negatively charged ( z ≈ −35 mV) DOPE/DOPG membranes (results not shown). As a consequence of this, Laponite nanoparticles do not induce leakage in DOPE/DOPG liposomes in the range 0.5–200 ppm for 10 mM Tris, pH 7.4 (Figure A).…”

“…While such nanoparticles were not found to provide any protection of LDH-bound LL-37 against proteolytic degradation, they were demonstrated to offer other functional advantages, notably through their ability to flocculate Escherichia coli (E. coli), an effect again more pronounced for smaller particles …”

The Potential of Human Peptide LL-37 as an Antimicrobial and Anti-Biofilm Agent

“…Likewise, it appears that LL-37 facilitates the entry of gold nanoparticles (AuNPs) into the cell, resulting in an increased angiogenesis and improved wound healing [202]. When pairing LL-37 with double hydroxide nanoparticles, it is important to consider the size of the particle; smaller sized particles are more capable of binding to, and disrupting the anionic membrane of bacteria [203]. Furthermore, as described by Bitschar et al, LL-37 can synergize with the lanthionine-containing bacteriocins (lantibiotics) that are produced by commensal bacteria on the human skin.…”