Determination of rifampicin location in cholesterol-lipid liposomes by 2H and 31P Solid-State NMR

Liposome encapsulated rifampicin (RIF), a first line anti-tuberculosis agent, was prepared using the chloroform film method. Cryo-transmission electron microscopy of the Hposome showed a mixture of unilamellar and multilamellar vesicles with a size of 200-300 nm. The results correlated with those obtained from dynamic light scattering. Deuterated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (d-POPC) was used to prepare liposomes for solid-state nuclear magnetic resonance (SS-NMR). Cholesterol (CH), which orientates between the phospholipid molecules and affects the fluidity of the bilayer membrane, increased the physical stability of the liposome to longer than 4 weeks with increased CH content. Furthermore, SS-NMR results indicated that RIF was located between the methylene chains of the phospholipid bilayer, in association with CH molecules.