Vesiculas liposomales estabilizadas con quitosano: estudio electrocinético

Resum

The aim of this work is to prepare stable liposome suspensions coated by chitosan biopolymer by means of the ionic gelation process. Concentrated soybean lecithin suspensions were prepared by the slow swelling under shear method and then diluted with NaCl 10-5 mol/L to make liposomal dispersions ranging 0.1 to 0.5% w/v, with an average mean diameter around 250 nm. Chitosan (180 kDa) solution in HOAc 0.5% v/v ranging 0.010 to 0.250% w/v, were mixed together with the liposome suspensions and the effect of both chitosan and liposome concentration on the electrokinetic behavior of the coated liposomes was analyzed by monitoring the change in æ-potential and particle diameter. The particle charge changed from -70 mV in the absence of chitosan to +40 mV in the presence of chitosan, indicating complex formation between the anionic liposomes and cationic chitosan molecules. Below a minimum critical chitosan concentration (cmin), large aggregates were formed that phase separated within minutes, whose origin was attributed to formation of coacervates. On the other hand, above a maximum critical chitosan concentration (cmax), large flocs were formed that sedimented within hours, whose formation was attributed to depletion flocculation. Liposomes coated with chitosan in concentrations between these parameters were stable with time and had better stability to aggregation than uncoated liposomes. This study indicates that chitosan can be used to form biopolymer-coated liposomes with enhanced stability over uncoated liposomes.