Zhang Xian-Man, Patel Anant B, de Graaf Robin A, Behar Kevin L
Department of Psychiatry, New Haven, CT 06520-8043, USA.
Chem Phys Lipids. 2004 Jan;127(1):113-20. doi: 10.1016/j.chemphyslip.2003.09.013.
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.
