Generation of superparamagnetic liposomes revealed as highly efficient MRI contrast agents for in vivo imaging.
ABSTRACT Maghemite (gamma-Fe2O3) nanocrystals stable at neutral pH and in isotonic aqueous media were synthesized and encapsulated within large unilamellar vesicles of egg phosphatidylcholine (EPC) and distearoyl-SN-glycero-3-phosphoethanolamine-N-[methoxy(poly(ethylene glycol))-2000] (DSPE-PEG(2000), 5 mol %), formed by film hydration coupled with sequential extrusion. The nonentrapped particles were removed by flash gel exclusion chromatography. The magnetic-fluid-loaded liposomes (MFLs) were homogeneous in size (195 +/- 33 hydrodynamic diameters from quasi-elastic light scattering). Iron loading was varied from 35 up to 167 Fe(III)/lipid mol %. Physical and superparamagnetic characteristics of the iron oxide particles were preserved after liposome encapsulation as shown by cryogenic transmission electron microscopy and magnetization curve recording. In biological media, MFLs were highly stable and avoided ferrofluid flocculation while being nontoxic toward the J774 macrophage cell line. Moreover, steric stabilization ensured by PEG-surface-grafting significantly reduced liposome association with the macrophages. The ratios of the transversal (r2) and longitudinal (r1) magnetic resonance (MR) relaxivities of water protons in MFL dispersions (6 < r2/r1 < 18) ranked them among the best T2 contrast agents, the higher iron loading the better the T2 contrast enhancement. Magnetophoresis demonstrated the possible guidance of MFLs by applying a magnetic field gradient. Mouse MR imaging assessed MFLs efficiency as contrast agents in vivo: MR angiography performed 24 h after intravenous injection of the contrast agent provided the first direct evidence of the stealthiness of PEG-ylated magnetic-fluid-loaded liposomes.
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ABSTRACT: Magnetic separation technology is a quick and easy method for sensitive and reliable detection, separation, and purification of biomolecules from any medium. Dopamine plays a crucial role for human metabolism; hence the development of selective and robust interference free methods for dopamine (DA) detection is of great importance. In the present study, we have reported an alternative method for the detection of DA which overcomes interference by coexisting compounds. We have designed a magnetically stabilized fluidized bed system (MSFB) by using fluorescein isothiocyanate (FITC) conjugated magnetic graphene oxide sheets (magGOs) as preconcentrator and diagnostic tool. In the presence of coexisting molecules, ascorbic acid (AA) and uric acid (UA), FITC-magGOs showed selectivity to DA as 39- and 34-folds, respectively. Compared with DA, a negligible amount of AA and UA were captured by FITC- magGOs non-specifically. Maximum DA adsorption capacity of FITC-magGOs was found to be 46.21 mg/g. The characteristics of the DA adsorption behavior were described by the application of the Langmuir isotherm model with monolayer adsorption more accurately. All experiments were carried out in the neutral solutions at around physiological pH.Separation Science and Technology 11/2013; 48(17):2608-2615. DOI:10.1080/01496395.2013.807289 · 1.20 Impact Factor
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ABSTRACT: The aim of this work was to construct carboxymethyl dextran (CMD)-coated magnetoliposomes (MLs), another stealth MLs alternative to PEGylated MLs, for theranostic application. Particularly, the on-demand release of CMD-MLs under low-frequency alternating magnetic field (LF-AMF) was studied. We found that as-prepared MLs exhibited good stability and high drug loading ability for doxorubicin (DOX). Cytotoxicity assay against human neuroblastoma SH-SY5Y cells showed that the DOX-loaded CMD-MLs were less toxic than free DOX due to the sustained release of DOX. However, the release of DOX-loaded CMD-MLs was enhanced by low-frequency alternating magnetic field without hyperthermia generation. The MLs also acted as an efficient T2-weighted contrast agent during in vitro MRI measurements. The above results provide useful information on in vivo diagnostic/therapeutic efficacy of DOX-loaded CMD-MLs for some cancers, such as brain cancers. Copyright © 2014 Elsevier Ltd. All rights reserved.Carbohydrate Polymers 03/2015; 118C:209-217. DOI:10.1016/j.carbpol.2014.10.076 · 3.92 Impact Factor
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ABSTRACT: To address the limitations of systemic drug delivery, localized drug delivery systems (LDDS) based on nano-engineered drug-releasing implants are recognized as a promising alternative. Nanoporous anodic alumina (NAA) and nanotubular titania (TNT) fabricated by a simple, self-ordering electrochemical process, with regard to their outstanding properties, have emerged as one of the most reliable contenders for these applications. This review highlights the development of new LDDS based on NAA and TNT, focusing on a series of strategies for controlling their drug release characteristics that are based on: modification of their nanopore/nanotube structures, altering internal chemical functionalities, controlling pore openings by biopolymer coatings and using polymeric micelles as drug nano-carriers loaded within the implants. Several new strategies on externally triggered stimuli-responsive drug release for LDDS are also reviewed, and their significance toward the development of advanced smart implants for localized therapy is discussed. Finally, the review is summarized with conclusions and future prospects in this research field.01/2014; 2(1):10. DOI:10.1039/c3bm60196j