LIPID BILAYERS INCLUDING CHOLESTEROL AS VEHICLES FOR ACID DYES IN WOOL DYEING

We describe the use of large unilamellar liposomes of a defined size and containing cholesterol as vehicles in commercial dyeing of untreated wool with a milling acid dye. To this end, we have investigated liposomes prepared with egg phosphatidylcholine (PC) and cholesterol (CH) at different lipid compositions (from 10:0 to 8:2 molar ratios) containing the commercial acid dye Polar blue G, CI acid blue 90. We assessed the physical stability of these systems by measuring the mean vesicle size of the suspensions during dyeing. We also investigated kinetic aspects involving dye adsorption and bonding to untreated wool samples at different PC:CH lipid compositions. Increasing amounts of CH in bilayers enhance both the physical stability of complete liposomes and the inhibition of dye exhaustion on untreated wool. Using only the dye trapped in bilayers, dyeing kinetics follows a different tendency, reaching the maximum initial inhibition and final exhaustion for the PC:CH 8.5:1.5 molar ratio. Bonding of dye to wool fibers also improves, reaching the optimum value for the PC: CH molar ratio 8.5:1.5 in all cases. The smoothness of dyed wool samples is also enhanced, the best results being reached with the highest proportion of CH.