A. M. Manich

The formation of liposomes in vitro by mixtures of lipids modeling the composition of the stratum corneum

Abstract The influence of different synthetic lipid mixtures approximating the composition of stratum corneum on the formation and physicochemical properties of liposomes was investigated with the aim of characterizing these structures. To this end, a lipid mixture containing ceramide (40%), cholesterol (25%), palmitic acid (25%) and cholesteryl sulfate (10%) was chosen as a central composition of the optimizing Box and Behnken experimental model for three variables. From these compositions, the optimizing lipid percentage range was varied for each lipid ±15%, except for the cholesteryl sulfate in which case the variation was extended to ±100%. Liposomes were prepared by sonication at 63 °C in a buffered medium (100 mM NaCl, 5 mM TRIS) at pH 7.5 and supplemented in some cases with 10 mM of 5(6)-carboxyfluorescein. The vesicle size distribution of liposome suspensions (nm) was determined by photon correlation spectrometry, whereas the internal volume (ml per mmol lipid) was determined by spectrofluorometry. Transmission electron microscopy (TEM) reveals the presence of unilamellar liposomes in all the lipid mixtures investigated. With regard to the physicochemical properties of the systems, increasing concentrations of ceramide, palmitic acid and cholesterol (or low cholesteryl sulfate concentrations) result in a decrease in both the size of the vesicles and the internal volume of these structures. This direct correlation confirms the formation of similar bilayer structures in all cases.

Percutaneous penetration of liposomes using the tape stripping technique

The reservoir capacity of the stratum corneum was studied by topical application of sodium fluorescein encapsulated in vesicles in order to elucidate the mechanism involved in the (trans)dermal transport of drugs when vesicles are applied to the skin. The penetration profile of sodium fluorescein in the different strips was found to be logarithmic with both the constant and the slope of the regression curves, accounting for the superficial non-penetration content and for the penetration rate inside the stratum corneum, respectively. The results show a small but significantly enhanced penetration of these vesicle structures for the release of hydrophilic substances. Moreover, similar values obtained when the same liposomes with a varying encapsulation content were applied could lend support to the penetration mechanism where the vesicle enhancement is mainly due to stratum corneum structural modification.

Abrasion Kinetics of Wool and Blended Fabrics

The abrasion resistance of different wool and blended fabrics is measured with the Martindale wear and abrasion tester, the abrasion kinetics is identified by the shape of the mass loss curve versus abrasion cycles up to yarn breakage. A concave kinetic curve shows a low initial weight loss rate, which continues to increase throughout the process up to the end. A convex kinetic curve begins with a high initial weight loss rate, which continues to decrease throughout the process. The third kinetic curve shows an almost linear relationship between mass loss and abrasion cycles up to yarn breakage. Due to the long time required for the abrasion test to yarn breakage, a simplified method is used based on the determination of mass loss up to 5000 abrasion cycles. The initial mass loss rate and the mean value of this rate throughout the 5000 abrasion cycles (i.e., the mean abrasion gradient) seem to be good estimates of the surface and structural abrasion degradation of the fabrics, and they show a strong relationship with the structural parameters of the fabrics.

Optimizing a Wool Dyeing Process with an Azoic 1:2 Metal Complex Dye Using Commercially Available Liposomes

We investigate the application of a commercially available phosphatidylcholine li posome suspension of defined size (about 100 nm) as a carrier for the azoic metal complex 1:2 dye Lanaset Yellow 2R to untreated wool fibers at the pilot plant level. To explore the influence of the experimental conditions on the dyeing process and on dyed yarn properties, we use a Box and Behnken factorial design for three variables. From this optimization study, we conclude that commercially available liposomes are suitable for dyeing wool at lower temperatures and shorter times than those needed in conventional industrial wool dyeing. Thus, wool may be dyed at 80°C using liposomes at 1 -2% owf with satisfactory dye exhaustion and fixation levels and good mechanical properties and handle. The main novelty of this procedure is the use of commercial liposomes as a simple dyebath additive. Increasing liposome concentrations in the dyebath improve dye exhaustion on the fibers at high temperatures, but dye fixation at these temperatures is independent of liposome concentration. depending instead on dye concentration. Liposomes also improve the leveling effect of the dye compared to that with conventional auxiliaries in all cases. Although liposome concentration does not significantly affect yarn mechanical properties, there is an optimal liposome concen tration that improves handle (yarn-to-yarn friction ).

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 sus pensions during dyeing. We also investigated kinetic aspects involving dye adsorption and bonding to untreated wool samples at different PC:CH lipid compositions. In creasing 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.

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.

The Influence of the Spinning Process, Yarn Linear Density, and Fibre Properties on the Hairiness of Ring-spun and Rotor- spun Cotton Yarns

Cotton–spun yarns from 34 staple stocks were manufactured by means of the ring–spinning process (34 yarns) and a rotor–spinning process (29 yarns) and tested for hairiness with the Shirley Hairiness Meter. For each spinning system, yarns were spun at two values of yarn linear density (15 and 30 tex for ring–spinning and 30 and 50 tex for rotor–spinning), but the twist multiplier was kept constant within the series for each spinning process. The higher hairiness of ring–spun yarns and an increase ln hairiness with the yarn linear density were confirmed. The effect of the fibre parameters on yarn hairiness explains only about 30% of the total effect for ring–spun yarns and 40% for rotor–spun yarns. Fibre length and its uniformity are the fibre properties having the greatest influence on the hairiness of both ring– and rotor–spun yarns, the Micronaire index having only slight influence on the hairiness of ring–spun yarn.

Elastic Recovery and Inverse Relaxation of Polyester Staple Fiber Rotor Spun Yarns

We have studied the elastic recovery and inverse relaxation phenomena of polyester staple fiber rotor spun yarns. Better fiber orientation obtained with a drawing passage before spinning results in higher permanent deformation and lower delayed elastic recovery of the yarn. Yarn twist has little influence on elastic characteristics. The stress produced in the yarn when strained at 10% is higher when fibers are straighter and lower when twist increases. The inverse relaxation effect increases with the level of orientation of the fibers in the yarn.

Phosphatidilcholine Liposomes as Vehicles for Disperse Dyes for Dyeing Polyester/Wool Blends

This study describes the role of liposomes as carriers in dyeing polyester/wool blends with disperse dyes. Dye exhaustion and bonding on polyester/wool samples are studied under different experimental conditions—the liposome amount, the dye amount, and the temperature—to achieve optimal conditions. The results are compared with those obtained with and without conventional dyeing auxiliary products. Although bath exhaustion is higher in the presence of commercial carriers, the dye bonded in creases markedly in the presence of liposomes in the two fibers. The role played by liposomes in polyester/wool blend dyeing can lead to a new strategy for this process.

Multilamellar liposomes including cholesterol as carriers of a 1:2 metal complex dye in wool dyeing

Studies are described of the use of multilamellar lipid vesicles (mlv) of defined size (400 nm) containing increasing amounts of cholesterol (ch) as carriers of a 1:2 metal complex dye to untreated wool fibers. We investigate liposomes made from egg phosphatidylcholine (pc) containing the CI Acid Yellow 129 dye (weakly polar 1:2 metal complex dye) at pc:ch molar ratios ranging from 10:0 to 6:4. The total lipid concentration of liposomes and the dye concentration remain constant (1.25 mmol and 1% owf, respectively). 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 involving dye adsorption and bonding on untreated wool samples by means of these liposomes are also investigated. This process leads to the controlled exhaustion of dye in wool samples, which depends on the liposome lipid composition. Increasing amounts of ch in bilayers result in a progressive rise in both dye exhaustion and total amounts of dye bonded to wool fibers. The diffusion properties of wool fibers as well as the smoothness of the dyed samples, given as a measure of their handle, also improve.