New Generation of Liposomic Products with High Migration Properties

New Generation of Liposomic Products with High Migration Properties

Martí, M

ABSTRACT

The usefulness of liposomes made up of phosphatidylcholine for wool dyeing has already been demonstrated. The dyeing temperature can be 100C lower than for conventional dyeing, with similar dye exhaustion and lower environmental impacts. However, conventional liposomes do not favor dye migration and do not achieve good leveling without synthetic auxiliaries. This work presents new strategic liposome formulations to increase migration phenomena in wool fabrics and yarn dyeing. The promising results obtained with these specific liposome formulations are compared with those using a number of commercial migrators such as Tanapal LM and Albegal SET in wool fabric dyeing with premetallized 2:1 (Lanaset) and 1:1 (Neolan) dyes.

Liposomes are vesicles formed by surface-active biological lipids. An internal aqueous domain is trapped between the lipidic bilayers. Phosphatidylcholine is the most widely used biological lipid for producing liposomes. The potential use of liposomes as auxiliaries in wool finishing is based on the similarity existing between the bilayer structure of the cell membrane complex (CMC) of the internal lipids and the liposome, the key role played by the CMC in transporting chemicals into fibers, and the importance of hydrophobic interactions in the structural organization of wool [20].

In our earlier work, we used liposomes composed of pure phosphatidylcholine or those containing lipids present in the CMC such as cholesterol as vehicles for aqueous chlorine solutions in wool chlorination [7, 8]. These applications improve both the regularity and homogeneity of these oxidative treatments, minimizing wool degradation and facilitating subsequent treatments in wool processing. Likewise, we investigated liposomes formed by phosphatidylcholine or those containing increasing proportions of cholesterol as carriers of commercial milling acid dyes, azoic disperse dyes, and 1:2 metal complex dyes in dyeing untreated wool samples at the laboratory level [4, 9-11]. Thereafter, we studied the use of liposomes for dyeing wool/polyester blends [18]. The presence of these bilayer structures in the dyebath resulted in a marked increase in the amount of dye fixed to the two fibers. In subsequent works, we extended these investigations by determining the effects of commercially available phosphatidylcholine liposomes on dyeing untreated wool yarn at the pilot plant level with the 1:2 metal complex dyes usually employed by the wool industry [2, 5]. In this case, we added liposomes to the dyebath as a simple additive with promising results.

At present, a commercial liposome exists in the textile market as a dyeing auxiliary for wool-Archicolor Transfer (Archivel Technologies, Spain). Traditionally, high temperature procedures (about 980C) and dyeing auxiliaries (synthetic compounds) have been extensively used. In both cases, the deleterious effects on textiles (fiber damage) and on the environment (contamination) are considerable. The main advantages of this process include a marked reduction in the temperature of the wool dyeing process using liposomes (about 1O0C) with the corresponding savings in energy, the ecological benefits of the process (avoidance of synthetic auxiliary products), and the final quality of the textile with improved smoothness and mechanical properties and increased material weight yield during subsequent spinning [3, 19], However, the wool industry is demanding a new generation of liposomes with high migration properties to be used for dyeing wool fabrics that have been subjected to deleterious chemical treatments in their processing before dyeing.

Our study focuses on the development of new liposome formulations with surfactant agents to enhance migration without losing their effect as a dyeing auxiliary for low temperature dyeing. A number of studies have sought to determine the interactions of surfactants with PC liposomes by studying the changes in these interactions |6, 13, 14]. When surfactants are incorporated into the phospholipidic bilayers, they bring about changes in their permeability. In our study, we use these liposome-based formulations to improve the migration characteristics of conventional textile liposomes with respect to a number of commercial migrators such as Albegal SET for dyeing with premetallized 2:1 Lanaset dyes and Tanapal LM for dyeing with premetallized 1:1 Neolan dyes.

Materials and Methods

Yarns of 100% pure wool 2/28 supplied by Nuova Superlana (Moniale, Italy) and wool fabrics knitted from R64/2 (count 2/28) yarns supplied by Descalzi (Spain) were the dye substrates. The 1:2 metal complex dye Lanaset Grey G and the 1:1 metal complex dye Neolan Red GRE 200 (Ciba, Switzerland) were the dyestuffs.

The commercial auxiliaries used as leveling-migrating agents were Tanapal LM (Sybron/ Tanatex, Japan), Albegal SET (Ciba, Switzerland), liposome Archicolor Transfer (20% lipids), and Biostoper (15% lipids) liposomes (Archive! Technologies, Spain). The cationic surfactant Emegal LYP and a pH regulator Emenil PAM were supplied by Emequimica (Sabadell, Spain). The nonionic surfactant Triton X-IOO (octylphenol polyethoxilated with K) units of ethylene oxide and active matter of 100%) was supplied by Tenneco SA (Barcelona, Spain).

Dyeing was performed in a Redchrome (Ugolini, Italy) laboratory machine equipped with a microprocessor from Becatron AG Datex-Miero (Müllheim, Switzerland). The dyebath pH was determined by a Titrator TTT2 apparatus (Radiometer, Denmark). Dyeings at the pilot plant scale were carried out in a Tints Enrich S. L. Laboratory autoclave of 50 L, equipped with a Malt CPA 2000 microprocessor. Dye migration was determined with the help of DE* (color difference), as evaluated by a Macbeth colorimeter Color-eye 3000.

Surfactant-liposome formulations X/Y (X being the % surfactant Emegal LYP and Y the % lipids from the liposome Biostoper) were prepared at the laboratory scale. In the migration tests, dyed and undyed samples were put into a blank dyebath, and the dye transferred to the undyed sample was measured by assessing the color difference between the two samples. These tests consisted of three steps: (1) Testimony wool dyeing: Wool fabrics were conditioned in a bath at pH 4.0 and 60°C for 15 minutes. Samples were then immersed in the dyebaths (bath ratio 1/25) prepared with 1% owf dye and 1 g/1 Emenil PAM. Dyeing was initiated at room temperature, and the temperature increased 1°C/minute until reaching the maximum temperature (98°C), then remained constant for 60 minutes. Samples were then rinsed with water and dried in an oven at 80°C for 20 minutes. (2) Migration dyeing: Dyed testimony and undyed wool samples were immersed in baths prepared with the auxiliary and 1 g/1 Emenil PAM. The dyeing cycle was the same, the final dyeing time being 30 minutes at 980C. (3) DE* evaluation: Color differences in the two wool samples were measured with a Macbeth colorimeter (illuminant D65 /10° observer), and the results were expressed according to the CIE Lab 1976 colorimetric formula [21]. In these tests, we used the DE* value to assess the migration level of the auxiliaries. The smaller the DE* between initial dyed and undyed samples, the greater the migration during migration dyeing.

Three kg of yarn wool cones were dyed at the pilot plant scale with a flow of 35.7 E/kg/minute in different dyebaths with 1% owf Lanaset Grey G, 0.1 cc/E Emectol SMA (Emequimica SA, Spain), 1 cc/E Esterai FA (Color Center, Spain), and the migrator auxiliary. Dyeing was initiated at 40°C and the temperature increased by 1°C/ min until 80°C, remaining constant for 15 minutes. After raising the temperature by 1°C/min until the final temperature was reached (90°C or 98°C), the temperature remained constant for 30 minutes, during which acetic acid was added to increase the final dye exhaustion. Dyebath exhaustion was determined by a Shimadzu UV265FW spectrophotometcr. The dyebath with liposome aliquots was added to quartz cuvettes filled with an aqueous solution of Triton X-100 (10 g/1); the interaction of the non-ionic surfactant Triton X-100 with the liposome structures resulted in solubilization of phospholipid vesicles by means of mixed micelle formation [16], turning the liposome suspension into clear solutions.

The vesicle size distribution and polydispersity index of liposomes and their mixture with cationic surfactant Emegal EYP were determined by a dynamic light scattering technique using a photon correlator spectrometer (Malvern Autosizer 470°c PS/MV). Samples were adjusted to the same concentration as the dyeing (1, 2, or 4% owf, b.r. 1/25). Quartz cuvettes were filled with the samples, and all the experiments were thermostatically controlled (25°C). The samples were measured at a scattering angle of 90°. Data thus obtained were analysed using the version of the program CONTIN provided by Malvem Instruments, England.

Turbidity measurements were used to confirm the presence of vesicles after mixing the liposomes with the surfactant. Samples were prepared at the same dye concentration (2 or 4% owf, b.r. 1/25). Absorbance as a turbidity value was determined by a Shimadzu UV265FW spectrophotometer (λ = 500 nm).

Results and Discussion

We used two dyestuffs, Lanaset and Neolan, to study the wool dyeing process on an industrial scale. Lanaset dyes are based on a mixture of products with similar dyeing characteristics. They contain acid milling, reactive, or 1:2 metal complex dyes, and therefore show good wet fastness properties. Dyeing is carried out at pH 4.5-5.0 with the auxiliary Albegal SET. In this pH range, fiber damage is minimized, with high levels of final dyebath exhaustion and hence good shade reproducibility. Lanaset dyes are used on loose fibers, tops, and yarns in package or hank form [15]. Neolan dyes are 1:1 metal complex dyes used on an industrial scale for loose stock and yarns for floor coverings, hank-knitting yarns, and piece goods. They exhibit excellent level dyeing and penetration characteristics and are especially suitable for dyeing non-neutralized carbonized and acid-milled wool. These dyes are commonly applied to wool in a strongly acidic (pH approximately 2) dyebath. Under these conditions, the dyes have good migration properties and thus suitable leveling characteristics [I].

We made preliminary assay with two different liposomes by changing their lipid composition (Archicolor Transfer and Biostoper). The results of migration tests with Lanaset Grey G of the two liposomes and their comparison with Albegal SET and without auxiliary are shown in Figure 1. Here, we see only a slight improvement in migration with Biostoper (color difference DE* is the smallest).

After testing the stability of the different surfactant/ liposome formulations and their affect on wool dyeing migration, we chose a cationic surfactant Emegal LYP to prepare several specific mixtures with the liposome Biostoper (Table 1).

We evaluated the migration effect of the different formulations at several concentrations using the dyeing conditions for Lanaset and Neolan dyes and compared the results with the effect of the conventional auxiliaries Albegal SET or Tanapal LM, respectively.

To achieve migration levels similar to those of Albegal SET, a 4% owf formulation with the highest surfactant content of 20/7.5 was needed because of the poor migration of the Lanaset Grey G. (Figure 2a). However, only 2% of the formulation with the lowest surfactant content of 5/7.5 was needed to achieve the same migration level of Tanapal with Neolan Red GRE 200, given its good migration properties (Figure 2b). As in the previous case, the higher the proportion of surfactant, the greater the migration effect.

Liposomes such as Archicolor Tranfer used to date for wool dyeing without surfactants enhanced their retardant effect in the early stages of the dyeing process, followed by the promotion of dye exhaustion at 80 or 85°C, allowing us to dye at 90°C with total dye exhaustion [3, 19]. To ascertain whether these surfactant/liposome formulations maintained this behavior, we performed a kinetic study with Lanaset Grey G at the pilot plant level at 90°C with the highest surfactant proportion at 4% owf, with the liposome without the surfactant, and with Albegal SET at 980C (Figure 3).

We obtained a higher exhaustion when there were liposomes in the bath regardless of the presence of surfactants, although the final temperature (90°C) was lower than the dyeing temperature with Albegal SET (98°C). There were also considerable differences at low temperatures. When we used mixture 20/7.5 at 4% owf concentration, there was high color retention in the dyebath. This behavior resembled that observed with Archicolor Transfer liposome [19]. It seems that this is advisable in order to achieve a uniform final color.

From the results presented to date, we can deduce that incorporating the surfactant into the liposome maintains the peculiar dyeing kinetic effects of conventional liposomes (delaying dye incorporation into the fibers at the beginning of the dyeing process and improving dye exhaustion at the end). Moreover, a certain dye migration occurs with increased surfactant added to the liposome.

We evaluated the spectrophotometric behavior of different liposome-surfactant formulations. The increased amount of surfactant present in the liposome induces a progressive increase in the absorbance (turbidity) of the liposome-surfactant system (Figure 4). Thus, these surfactant concentrations increase the size of the liposomes without disintegrating the vesicles.

We studied size distribution with light scattering to confirm the vesicle presence in the dyebath when using liposome-surfactant formulations (Table II). As expected, there was an increase in the size of the liposome vesicles. The liposome alone has a vesicle diameter of 102.6 nm and, in the case of mixture 5/7.5, the diameter is higher, (142.8 nm), in both cases with a monomodal distribution. Accordingly, the surfactant at this concentration is included in the bilayers, inducing an increase in their size [14]. In the case of mixture 20/7.5, there is a bimodal distribution. The size of the vesicles also increases, attaining a diameter of about 277.4 nm, but there are also a significant number of smaller particles (about 15 nm), which could be due to the presence of free micelles formed by the surfactant not included in the bilayers.

A number of factors can account for the results on dyeing kinetics and migration. In these mixtures, there are different kinds of structures: free molecules, micelles of surfactant, mixed micelles of surfactant and lipid, conventional liposome vesicles, and the same vesicles with surfactant molecules incorporated into the bilayers. The surfactant micelles could promote dye migration into the fibers in the same way as the commercial auxiliaries. Besides, the surfactant molecules incorporated into the bilayer of the liposome vesicles could induce a modification of their supramolecular structure. Some micellar structures could be formed in the interior of the liposome bilayer with a corresponding increase in the vesicle size, which could enhance dyestuffs migration [17]. Moreover, the liposome structures could also improve wool permeability, maintaining the inherent quality of liposomes during dyeing at low temperatures.

Conclusions

Two new surfactant/liposome formulations are presented in support of the migration in wool dyeing: a 4% owf of mixture 20/7.5 for Lanaset dyes and a 2% owf of mixture 5/7.5 for Neolan dyes. When these formulations are used, migration levels similar to those of Albegal SET or Tanapal LM are achieved. The presence of the surfactant in the formulations does not influence the kinetic curve of wool dyeing: for two reasons there is a delayed-action effect at low temperatures, which improves the uniformity of the final color, and a final high exhaustion is obtained even when a 9O0C final dyeing temperature is used.

ACKNOWLEDGMENTS

We are indebted to Emequimica SA and Nuova Superlana LTA for supplying the products and materials used in this work and to Archivel Technologies and the CICYT Program (PETRI 95-0597-OP) for financial support. We acknowledge the expert technical assistance of Mr. G. von Knorring.

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Manuscript received July 3, 2003: Accepted Ociober 17, 2003.

M. MARTÎ,1 A. DE LA MAZA, J. L. PARRA, AND L. CODERCH

IIQAB (CSIC), Barcelona 08034, Spain

S. SERRA

Tints Enrich S L, 08205 Sabadell (Barcelona), Spain

1 To whom correspondence should be addressed: Dr. Meritxell Marti, Institut de Investigacions Quimiques i Arabientals de Barcelona (CSIC), Jordi Girona 18-26, 08034 Barcelona, Spain, tel (34) 934 006 100, fax (34) 932 045 904, e-mail mmgesl@iiqab.csic.es

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