An improved NMR study of liposomes using 1-palmitoyl-2-oleoyl-sn-glycero-3-phospatidylcholine as model

Abstract

In this paper we report a comparative characterization of Small Unilamellar Vesicles (SUVs), Large Unilamellar Vesicles (LUVs) and Multilamellar Vesicles (MLVs) prepared from 1-palmitoyl-2-oleoyl-sn-glycero-3-phospatidylcholine (POPC), carried out using two NMR techniques, namely High Resolution NMR in solution and High Resolution-Magic Angle Spinning (HR-MAS). The size and size distributions of these vesicles were investigated using the dynamic light scattering technique. An improved assignment of the (1)H-NMR spectrum of MLVs is also reported.

Figure 1

POPC.

Figure 2

CONTIN analysis of the autocorrelation function for the sample of POPC LUVs: a monomodal distribution with an average hydrodynamic diameter of 145 ± 6 nm is obtained.

Figure 3

600 MHz ¹H-NMR spectra of different classes of POPC (50mg/mL) liposomes: a) HR-MAS spectrum of MLVs, 12kHz at 314.8 K; b) HR-MAS spectrum of LUVs, 12kHz at 314.8 K; c) 1H NMR spectrum of SUVs, no spinning at 320.0K. The arrows indicate the chemical shift position of CH₂-3.

Figure 4

¹H-¹H COSY map of POPC MLVs obtained using a spinning rate of 6 kHz. The calibrated temperature value of 303.9 K was obtained setting the temperature at 300.0 K.