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Molecular localization and state of amphotericin B in PEG liposomes
K Moribe1, K Maruyama, M Iwatsuru
1Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa, Japan.
Abstract:
We investigated the molecular localization and state of amphotericin B (AmB) encapsulated in polyethylene glycol (PEG)-coated liposomes. AmB-encapsulating PEG-liposomes composed of dipalmitoylphosphatidylcholine (DPPC), cholesterol (CH) and distearoyl-N-(monomethoxy poly(ethylene glycol)succinyl) phosphatidylethanolamine (DSPE-PEG, average MW of the PEG chain 2000) were prepared by hydration with 9% sucrose solution and extrusion. The amount of AmB encapsulated in the liposomes increased with incorporation of DSPE-PEG and decreased with that of CH. The molecular localization and state of AmB were investigated by PEG/dextran two-phase partition, potassium permeability measurement, fluorescence quenching measurement and circular dichroism (CD) spectroscopy. The results suggest that there are two types of AmB localization in PEG-liposomes, one of which corresponds to the complex of AmB with DSPE-PEG on the membrane surface, while the other corresponds to the pore form of AmB in the hydrophobic core of the liposomal membrane. AmB in PEG liposomes was present in both aggregated and monomeric states.
Insights
This study reveals amphotericin B (AmB) in PEG-liposomes exists in two locations and states: aggregated/monomeric and surface/pore-bound. This provides insights into antifungal drug delivery mechanisms.
Area of Science:
- Pharmaceutical Sciences
- Drug Delivery Systems
- Lipid Nanoparticles
Background:
- Amphotericin B (AmB) is a vital antifungal agent, but its use is limited by toxicity.
- Liposomal encapsulation, particularly with polyethylene glycol (PEG)-coated liposomes, is a strategy to improve AmB's therapeutic index.
- Understanding the precise molecular behavior of AmB within these nanocarriers is crucial for optimizing drug efficacy and safety.
Purpose of the Study:
- To elucidate the molecular localization and physical state of amphotericin B (AmB) within PEG-coated liposomes.
- To investigate the influence of liposomal composition, specifically dipalmitoylphosphatidylcholine (DPPC), cholesterol (CH), and distearoyl-N-(monomethoxy poly(ethylene glycol)succinyl) phosphatidylethanolamine (DSPE-PEG), on AmB encapsulation and behavior.
Main Methods:
- Preparation of AmB-encapsulating PEG-liposomes using DPPC, CH, and DSPE-PEG via hydration and extrusion.
- Utilized PEG/dextran two-phase partition, potassium permeability assays, fluorescence quenching, and circular dichroism (CD) spectroscopy to analyze AmB.
- Quantified AmB encapsulation efficiency in relation to DSPE-PEG and CH content.
Main Results:
- AmB encapsulation increased with DSPE-PEG incorporation and decreased with cholesterol (CH) content.
- Two distinct AmB localizations were identified: a complex with DSPE-PEG at the membrane surface and a pore-forming AmB within the hydrophobic core.
- Amphotericin B was found to exist in both aggregated and monomeric states within the PEG-liposomes.
Conclusions:
- PEG-liposomes accommodate AmB in distinct molecular arrangements, influencing its interaction with the lipid bilayer.
- The presence of both surface-bound and pore-forming AmB, along with aggregated and monomeric states, offers a comprehensive understanding of AmB's behavior in this drug delivery system.
- These findings contribute to the rational design of improved AmB-based liposomal formulations for enhanced antifungal therapy.