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For targeted drug delivery a variety of protector or carrier systems has been developed. One of the promising approaches uses liposomes, which may be partially directed toward particular types of cells by means of antibodies or other ligands. We have proposed recently a new method for drug targeting based on magnetoliposomes, which are liposomes with subdomain magnetite (Fe3O4) particles with a diameter of ≈10 nm incorporated in their bilayers. Due to their magnetic sensitivity a non-homogeneous magnetic field may be used for the targeting of magnetoliposomes to a given tissue. Because magnetite particles are strong microwave absorbers we have experimentally analyzed the influence of microwave radiation with a frequency of 2.45 GHz on the permeability of phosphatidylcholine magnetoliposomes. We have found for example that microwave radiation with specific absorbed power of 400 mW/g almost completely releases entrapped 6-carboxy-fluorescein in 15 min. The probable underlying mechanism is heating of Fe3O4 particles which leads to a perforation of lipid bilayers and subsequent leakage of entrapped magnetoliposome volume, so microwave radiation may be used for controllable release of drugs at low doses of microwave radiation intensities as compared with conventional microwave hyperthermia used previously by other authors.
Liposomes made from dipalmitoyl-phosphatidylcholine and containing 6-carboxyfluorescein and dextran-magnetite entrapped in their aqueous interior compartments have been irradiated with a picosecond laser pulses. Substantial amounts of carboxyfluorescein were released in response to a single picosecond laser pulse and almost complete release was achieved using four laser pulses, which may be useful for laser induced delivery of therapeutic agents and other applications of lasers in biological systems.
Immunomagnetic systems have been used for positive selection of the cell fraction from a mixture using appropiate surface markers with satisfactory results, as hematopoietic CD34+ cells. In this work, we report the development of poly(ethylene glycol) (PEG)-grafted immunoliposomes loaded with dextran-magne-tite particles as the separation vehicles for immunomagnetic separation techniques. The magnetic ferrofluid was encapsulated into PEG-liposomes by the FTS methodology. The magnetoliposomes had a liposomal size around 800 nm and a Fe/lipid molar ratio of 0.87±0.30, and were retained in the magnetic field created by the MiniMACS system. Anti-CD34 immunomagnetoliposomes were prepared by coupling the My10 mAb and bound specifically to CD34+ KG-1a cells in culture and in mixtures with CD34- CHO cells. The magnetic cell sorting was carried out in cell mixtures KG-1a/CHO with a 10% initial of CD34+ KG-1a cells. The purity of the MiniMACS-positive fraction and the capture efficiency depended on the liposome concentration and antibody density used, related to the nonspecific cell binding of immunomagnetoliposomes due to the ferrofluid adsorbed and to the presence of whole antibody molecules in the liposome surface. The CD34+ cells isolated retained viability with an estimated recovery of 45-50%.
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