Determination of liposomal encapsulation efficiency using proton NMR spectroscopy |
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Authors: | Zhang Xian-Man Patel Anant B de Graaf Robin A Behar Kevin L |
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Institution: | Department of Psychiatry, New Haven, CT 06520-8043, USA. xian-man.zhang@yale.edu |
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Abstract: | A rapid and simple approach using 1H NMR was developed for determination of liposomal encapsulation efficiency without the need for physical separation of entrapped and non-entrapped marker. Measurements were made using a marker (homocarnosine) with a pH-sensitive 1H chemical shift in the presence of a pH gradient across the phospholipid vesicle membrane, or by addition of the chemical shift reagent, thulium(III)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra-(methylene phosphonic acid sodium salt) (TmDOTP5-). The measured encapsulation efficiencies for the liposomal dispersions prepared from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) through extrusion using 50, 200 and 1000 nm polycarbonate membranes were found to be identical using the two different experimental approaches. |
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Keywords: | Encapsulation efficiency Homocarnosine Proton NMR Liposome DPPC pH gradient Chemical shift reagent |
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