CONICET | Buscador de Institutos y Recursos Humanos

In particulate systems such as liposomes, concentration units are not enough to describe the drug distribution in suspensions, as they are not homogeneous. In certain in vitro assays, exposure to different number of particles (containing the same amounts of active in the same global volume) introduces an extra variable regarding to contact phenomena. Volume and area of liposomes decrease upon extrusion, while their quantity grows, as new vesicles are formed. Aiming to a rapid estimation of the number of unilamellar liposomes present in a suspension, a mathematical method was developed, based on the area and molecular weight of lipids and the mean size of the liposomes. Unilamellar liposomes loaded with a probe were prepared by extrusion and counted by fluorescence microscopy and Tunable Resistive Pulse Sensing (Q-Nano). Size was determined by Dynamic Light Scattering. There was about a 90% coincidence between the theoretical results and the number of unilamellar liposomes counted for two liposomes populations of different mean size. This model could be a useful complement for interpretation of in vitro experiments in which results could depend on the distribution of actives into different quantities of liposomes.