title: Determination of liposomal encapsulation efficiency using proton NMR spectroscopy.
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.
authors.affiliation: Department of Psychiatry, New Haven, CT 06520-8043, USA. xian-man.zhang@yale.edu
authors.forename: Xian-Man
authors.initials: XM
authors.lastname: Zhang
authors.forename: Anant B
authors.initials: AB
authors.lastname: Patel
authors.forename: Robin A
authors.initials: RA
authors.lastname: de Graaf
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Behar
mesh_terms: D002336:Carnosine / Q000031:analogs & derivatives* / Q000737:chemistry*; D003903:Deuterium / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008081:Liposomes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009942:Organometallic Compounds / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry; D011522:Protons
chemical_list: D008081:Liposomes; D009942:Organometallic Compounds; D009943:Organophosphorus Compounds; D010743:Phospholipids; D011522:Protons; C069929:thulium(III) 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetramethylenephosphonate; C005038:homocarnosine; D002336:Carnosine; D003903:Deuterium