31P-NMR study to determine the structure of nanodispersions in contrast to the standard bi-layer of liposomes
Liposomes have been used for years as a delivery agent in medical and commercial applications. Liposomes deliver mainly hydrophilic (water-soluble) compounds within the water core and a limited amount of hydrophobic (non-water soluble) compounds within the phospholipid bi-layer. A new type of liposome, termed a nanodispersion, is capable of encapsulating significantly higher concentrations of hydrophobic material due to the addition of a co-surfactant. The nanodispersion structure that allows for significantly more hydrophobic material to be encapsulated was unknown. The structure was determined using 31Phosphorus Nuclear Magnetic Resonance (31PNMR) and shift reagents. 31P-NMR produced spectra characterizing liposomes and nanodispersions. The liposome spectra were then compared to the nanodispersion spectra.31P-NMR was used to characterize the phospholipid bi-layer. The phosphorus atom's resonance was altered by the presence of a shift reagent added to the exterior of the liposomes and nanodispersions. Two peaks were identified as the interior and exterior layers of phospholipids in the 31P-NMR spectra of liposomes. One peak was identified in the 31P-NMR spectra of nanodispersions, shifted from its original position by the shift reagent. 31P-NMR of nanodispersions identified a single shifted phosphorus signal signifying a phospholipid mono-layer encompassing an oil core.
© Copyright 2009 Marcus T. Liotta