Article

Magnetoliposomes with high USPIO entrapping efficiency, stability and magnetic properties

Laboratory of Pharmaceutical Technology, Dept. of Pharmacy, School of Health Sciences, University of Patras, Patras, Greece.
Nanomedicine: nanotechnology, biology, and medicine (Impact Factor: 6.16). 06/2011; 7(5):572-9. DOI: 10.1016/j.nano.2011.06.010
Source: PubMed

ABSTRACT

The DRV technique (followed by extrusion) was used for construction of hydrophilic-USPIO encapsulating liposomes. Magnetoliposomes (ML) were characterized for size, surface charge, entrapment, physical stability and magnetic properties (relaxivity). Results show that nanosized extruded-DRV MLs encapsulate higher amounts of USPIOs in comparison with sonicated vesicles. Fe (III) encapsulation efficiency (EE) is 12%, the highest reported to date for nanosized MLs. EE of MLs is influenced by ML membrane composition and polyethyleneglycol (PEG) coating. PEG-coating increases ML EE and stability; however, r(2)-to-r(1) ratios decrease (in comparison with non-PEGylated MLs). Most ML-types are efficient T2 contrast agents (because r(2)-to-r(1) ratios are higher than that of free USPIOs). Targeted MLs were formed by successfully immobilizing OX-26 monoclonal antibody on ML surface (biotin-streptavidin ligation), without significant loss of USPIOs. Targeted MLs retained their nanosize and integrity during storage for 1 month at 4 °C and up to 2 weeks at 37 °C.

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    • "Due to the considerable size difference between the NPs (∼20 nm) and SUVs (∼100 nm), we have used SEC using Sepharose CL-4B columns with smaller pore sizes to separate the unbound NPs from the liposomes. SEC is an efficient method to separate the molecules based on their size and widely used to free the encapsulated liposomes from the surrounding particles [33] [34] [35]. DLS results revealed a mean hydrodynamic radius of the control SUVs and NPs loaded SUVs in the range between 100 to 110 nm (PDI = 0.15 ± 0.02) (n = 3). "
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    • "It is interesting to compare the iron to lipid ratio obtained with other magnetoliposomes [28] to that in the system developed here where this ratio is ten times lower. The volume fraction of SPION in the magnetoliposomes developed in this work was always very low and, this observation is important to eliminate the possibility of severe aggregation to explain the relaxivity results. "
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    • "Due to the considerable size difference between the NPs (∼20 nm) and SUVs (∼100 nm), we have used SEC using Sepharose CL-4B columns with smaller pore sizes to separate the unbound NPs from the liposomes. SEC is an efficient method to separate the molecules based on their size and widely used to free the encapsulated liposomes from the surrounding particles [33] [34] [35]. DLS results revealed a mean hydrodynamic radius of the control SUVs and NPs loaded SUVs in the range between 100 to 110 nm (PDI = 0.15 ± 0.02) (n = 3). "
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