Determination of the size distribution of lecithin liposomes: a comparative study using freeze fracture, cryoelectron microscopy and dynamic light scattering

The size distribution of liposomes is often determined using freeze fracture, cryoelectron microscopy or dynamic light scattering. However, the resulting size distributions do not directly coincide owing to the different weighting of the techniques. We present several methods which correct for these effects and allow a comparison of liposome size distributions as obtained by freeze fracture, cryoelectron microscopy or dynamic light scattering. These methods are based on theoretical models for the weighting of the size distribution of liposomes, which result from the preparation procedure for freeze fracture electron microscopy and from the measurement by dynamic light scattering. The proposed transformation methods are then experimentally tested with a sample of lecithin liposomes, whose size distribution was determined by dynamic light scattering, freeze fracture and cryoelectron microscopy. Furthermore, the weaknesses of the experimental techniques and hence of the resulting size distributions are discussed.