Multilamellar liposomes including cholesterol as carriers of azobenzene disperse dyes in wool dyeing

We have investigated multilamellar lipid vesicles (MLV) of defined size (400 nm) containing increasing amounts of cholesterol (CH ) as carriers of azobenzene disperse dyes to wool fibers. The liposomes are made from egg phosphatidylcholine (PC) and contain CI Disperse Orange 1 at different PC : CH relative concentrations. The physical stability of these systems is assessed by measuring the mean vesicle size distribution of the vesicle suspensions after preparation and during the dyeing process. Kinetic aspects involve dye adsorption and bonding on untreated wool samples by means of MLV liposomes at different PC : CH ratios. This process leads to the controlled ex haustion of dye in wool samples, which depends on the liposome lipid concentration. Increasing amounts of CH in bilayers result in a slight decrease in the dye exhaustion, although improving the total amounts of dye bonded to wool fibers. The optimum balance is reached for the maximum concentration of CH in bilayers, using the dye/ lipid weight ratio corresponding to the maximum encapsulation efficiency of the dye. This technological application also improves the dispersing efficiency of these systems with respect to the use of conventional dispersing agents.