Magnetic liposomes

Glpgard, C., Stensrud, G., and Aime, S. (2003) Novel radical-responsive MRI contrast agent based on paramagnetic liposomes. Magnetic Resonance in Chemistry, 41, 585-588. 

External stimuli have also been used to further target liposomes. In one such study magnetite particles were incorporated in radiolabeled liposomes and a magnet positioned over the right kidney of a test animal. The liposomes were selectively targeted to that kidney in concentrations that were viewed as significantly high for relevant clinical applications [66],... 

The incorporation of magnetic particles in liposomes, combined with an externally applied magnetic field, has recently demonstrated in vivo the ability to slectively target a specific organ, i.e., one kidney over the other [155]. 

Fig. 5 Membrane models for NMR structure analysis, (a) An isotropic detergent micelle (left) is compared to the dimensions of lipid bilayers (right), (b) Macroscopically oriented membrane samples can be prepared on solid support, as nanodiscs, or as magnetically oriented bicelles. (c) Nomenclature and variability of liposomes small (SUV, 20-40 nm), intermediate (IUV, 40-60 nm), large (LUV, 100-400 nm), and giant unilamellar vesicles (GUV, 1 pm) multi-lamellar (MLV), oligo-lamellar (OLV) and highly heterogeneous multi-oligo-lamellar vesicles (MOLV)...

Peleg-Shulman T, Gibson D, Cohen R, Abra R, Barenholz Y. Characterization of sterically stabilized cisplatin liposomes by nuclear magnetic resonance. Biochim Biophys Acta 2001 1510 278-291. 

Figure 3 P NMR spectrum of SUV liposomes with 20 mol% incorporated STPP. Spectrum was taken using a VARIAN Mercury 300 NMR spectrometer, 5P as indicated in the figure. Abbreviations NMR, nuclear magnetic resonance STPP, stearyl triphenylphosphonium SVV, small unilamellar vesicle. Source From Ref 30.

Figure 3 Molecular relaxivities of liposomes with different Gd-containing membranotropic chelators. Liposomes (egg lecithin cholesterol chelator = 72 25 3) were prepared by consecutive extrusion of lipid suspension in HEPES buffered saline, pH 7.4, through the set of polycarbonate filters with pore size of 0.6, 0.4, and 0.2 mm. Liposome final size was between 205 and 225 nm. Gd content determination was performed by Galbraith Laboratories, Inc. The relaxation parameters of all preparations were measured at room temperature using a 5-MHz RADX nuclear magnetic resonance proton spin analyzer. The relaxivity of liposomes with polymeric chelators is noticeably greater because of the larger number of Gd atoms bound to a single lipid residue [16].

Schwendener, R. A., Wuethrich, R., Duewell, S., Westera, G., and Von-Schulthess, G. K. Small unilamellar liposomes as magnetic resonance contrast agents loaded with paramagnetic manganese-, gadolinium-, and iron-DTPA-stearate complexes. Int. J. Pharm. 1989, 49, 249-259. 

Trubetskoy, V. S., and Torchilin, V. P. New approaches in the chemical design of Gd-containing liposomes for use in magnetic resonance imaging of lymph nodes. J. Liposome Res. 1994, 4, 961-980. 

Ramundo-Orlando, A., Mattia, E, Palombo, A., and D Inzeo, G. (2000). Effect of low frequency, low amplitude magnetic fields on the permeability of cationic liposomes entrapping carbonic anhydrase, part II. Bioelectromagnetics, 21,499-507. 

Jain, S., et al. 2003. RGD-anchored magnetic liposomes for monocytes/neutrophils-mediated brain targeting. Int J Pharm 261 43. 

I 6 van den Bos EJ, Wagner A, Mahrholdt H, et al, Improved efficacy of stem cell labeling for magnetic resonance imaging studies by the use of cationic liposomes. Cell Transpl 2003 12 743-756. 

NMR technique. NMR-active metal ions entrapped in the liposome can be differentiated from those outside by the addition of shift reagents such as Dy(III) or Gd(III) to the external phase. Then metal concentrations inside and outside the liposome can be determined directly. This is attractive for 7Li+, 23Na+, and 39K+ ions because of high sensitivities and natural abundances. The direct determination of the metal ion concentrations are attractive but limited only for slow kinetics. When the rate becomes faster, line shape analysis or magnetization-inversion transfer techniques are employed. The latter method has been successfully applied to gramicidin channels,143 144 but not to artificial ion channels. 

Wheat starch lysophospholipid forms tiny liposomes in water that could readily be transported into the interior of a starch granule during its development. Solid-state nuclear magnetic resonance spectroscopy suggests that the phospholipids in wheat starch are predominantly complexed with amylose in an amorphous form in the granules.354-356... 

Saito, R., Bringas, J. R., McKnight,T. R.,Wendland, M. F., Mamot, C., Drummond, D. C., Kiprotin, D. B., Park, J. W., Berger, M. S., and Bankiewicz, K. S. (2004), Distribution of liposomes into brain and rat brain tumor models by convection-enhanced delivery monitored with magnetic resonance imaging, Cancer Res., 64, 2572-2579. 

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