Characterization of restricted diffusion in uni- and multi-lamellar vesicles using short distance iMQCs

Document Type

Article

Abstract

Improved understanding of the entrapment, transport, and release of drugs and small molecules within vesicles is important for drug delivery. Most methods rely on contrast agents or probe molecules; here, we propose a new MRI method to detect signal from water spins with restricted diffusion. This method is based on intermolecular double quantum coherences (iDQCs), which can probe the restricted diffusion characteristics at well-defined and tunable microscopic distance scales. By using an exceedingly short (and previously inaccessible) distance, the iDQC signal arises only from restricted diffusion spins and thereby provides a mechanism to directly image vesicle entrapment, transport, and release. Using uni- and multi-lamellar liposomes and polymersomes, we show how the composition, lamellar structure, vesicle size, and concentration affects the iDQC signal between coupled water spins at very short separation distances. The iDQC signal correlates well with conventional diffusion MRI and a proposed biexponential (multicompartmental) diffusion model. Finally, the iDQC signal was used to monitor dynamic changes in the lamellar structure as temperature-sensitive liposomes released their contents. These short distance iDQCs can probe the amount and diffusion of water entrapped in vesicles, which may be useful to further understand vesicle properties in materials science and drug delivery applications. © 2012 Elsevier Inc. All rights reserved.

Keywords

Intermolecular multiple quantum coherences, Liposomes, Restricted diffusion

Publication Date

10-1-2012

Publication Title

Journal of Magnetic Resonance

ISSN

10907807

E-ISSN

10960856

Volume

223

First Page

31

Last Page

40

PubMed ID

22975234

Digital Object Identifier (DOI)

10.1016/j.jmr.2012.07.021

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