Fusion between fluid liposomes and intact bacteria: study of driving parameters and in vitro bactericidal efficacy

Abstract

Background Pseudomonas aeruginosa represents a good model of antibiotic resistance. These organisms have an outer membrane with a low level of permeability to drugs that is often combined with multidrug efflux pumps, enzymatic inactivation of the drug, or alteration of its molecular target. The acute and growing problem of antibiotic resistance of bacteria to conventional antibiotics made it imperative to develop new liposome formulations for antibiotics, and investigate the fusion between liposome and bacterium. Methods In this study, the factors involved in fluid liposome interaction with bacteria have been investigated. We also demonstrated a mechanism of fusion between liposomes (1,2-dipa lmitoyl-sn-glycero-3-phosphocholine [DPPC]/dimyristoylphosphatidylglycerol [DMPG] 9:1, mol/mol) in a fluid state, and intact bacterial cells, by lipid mixing assay. Results The observed fusion process is shown to be mainly dependent on several key factors. Perturbation of liposome fluidity by addition of cholesterol dramatically decreased the degree of fusion with P. aeruginosa from 44% to 5%. It was observed that fusion between fluid liposomes and bacteria and also the bactericidal activities were strongly dependent upon the properties of the bacteria themselves. The level of fusion detected when fluid liposomes were mixed with Escherichia coli (66%) or P. aeruginosa (44%) seems to be correlated to their outer membrane phosphatidylethanolamine (PE) phospholipids composition (91% and 71%, respectively). Divalent cations increased the degree of fusion in the sequence Fe 2+ > Mg 2+ > Ca 2+ > Ba 2+ whereas temperatures lower than the phase transition temperature of DPPC/DMPG (9:1) vesicles decreased their fusion capacity. Acidic as well as basic pHs conferred higher degrees of fusion (54% and 45%, respectively) when compared to neutral pH (35%). Conclusion Based on the results of this study, a possible mechanism involving cationic bridging between bacterial negatively charged lipopolysaccharide and fluid liposomes DMPG phospholipids was outlined. Furthermore, the fluid liposomal-encapsulated tobramycin was prepared, and the in vitro bactericidal effects were also investigated.

Cracking Open Bacterial Membrane Vesicles

“…Reducing intermembrane hydration repulsion, decreasing bilayer surface density or polarity, and increasing the hydrophobicity of the intermembrane hydrophilic region are known to bring two membranes in close contact (Ohki, 1982;Cevc et al, 1985;Rand and Parsegian, 1989;Burgess et al, 1992;Mondal Roy and Sarker, 2011). Kadurugamuwa suggested that two divalent cations, Mg 2+ and Ca 2+ , which form salt bridges between MVs and the outer membrane, initiate membrane fusion and deliver the autolysin cargo to the cell (Kadurugamuwa and Beveridge, 1996;Wang et al, 2016;Oshima and Sumitomo, 2017). Tashiro and colleagues showed that Buttiauxella agrestis MVs selectively interact with Buttiauxella species.…”

Liposomal Nanovesicles for Efficient Encapsulation of Staphylococcal Antibiotics

“…4,5 Liposomes are vesicles in which an aqueous volume (which can encapsulate hydrophilic compounds) is enclosed by a spherical lipid bilayer (which can encapsulate hydrophobic compounds) typically composed of phospholipids and additional agents like cholesterol. 6 The liposomal lipid bilayer interacts directly with the lipids comprising the cell/bacteria membrane, thus delivering the cargo directly to the cell membrane without having to rely on active or passive uptake of the nanovehicle by target bacterial cells; 7 this makes liposomes specifically advantageous for the localized delivery of high loads of potentially toxic agents that cannot be administered systemically.…”

Hybrid cell reactor system from Escherichia coli protoplast cells and arrayed lipid bilayer chamber device

“…However, this is reasonable considering that liposome-liposome or liposome-planner bilayer fusion generally does not frequently occur unless using a chemical or electrical stimulus 54 , 55 . Several studies showed that in the absence of fusion enhancing reagents or stimulus, the liposome-liposome fusion does not occur or even at the best cases several times per 100 μm 2 56 – 60 . The fusion rate of protoplast into ALBiC bilayer corresponds to 1.5~2.3 × 10 −2 times per 100 μm 2 within the reported values.…”