Pathways for Dye Diffusion in Wool Fibers

Abstract

The most prominent view of the diffusion mechanism of dyes into wool fibers assumes that the molecules primarily enter the fiber in a fast process along the cell membrane complex (CMC), that is, by an intercellular mechanism. From the CMC, they are subsequently distributed in a slower process throughout the other morphological components according to their respective diffusion coefficients and dye affinities. This view, referred to here as the CMC-diffusion model, is based on investigations of the diffusion performance of heavy metal complex and fluorescent dyes under anhydrous and aqueous conditions. An evaluation of various key aspects of the evidence for this model suggests that, due to differences in the glass transition and fluorescence quenching performance of the various morphological components in a wool fiber, there is, in fact, little evidence to support the CMC-diffusion model. Instead, the evidence supports the alternative, more general view that under normal dyeing conditions, diffusion proceeds primarily by means of all the nonkeratinous components of the wool fiber according to a restricted transcellular diffusion mechanism.

In Vitro Contamination of Hair by Marijuana Smoke

“…A 5-min exposure of hair to an aqueous solution containing 1 mg/L cocaine hydrochloride was sufficient to produce measurable cocaine concentrations of 0.2 g/g of hair (34 ). From experiments involving dyestuffs (35)(36)(37) and drugs such as opiates (38 ), it can be assumed that, in intact hair, diffusion via the cuticle cell edges along the endocuticle and the cell membrane complex proceeds rapidly. From there, solutes are probably further distributed throughout the other morphologic components of hair by a slower process.…”

“…From experiments on diffusion of dyestuffs and drugs, there is also evidence that adsorption and diffusion of foreign matter is strongly influenced by the hair morphology (35)(36)(37)(38). Scalp hair plays an important role in individual appearance and, therefore, is frequently subjected to cosmetic treatments such as perming or bleaching.…”

Lipid Role in Wool Dyeing

“…However, the lower resolution of the light microscope, compared with the transmission electron microscope, restricts the amount of information that can be obtained by this technique. Wortmann et al (Wortmann et al, 1997) summarized different ideas about this subject. They justified that due to the CMC size in the fiber, intercellular pathway appears questionable.…”

“…But only the two latter ones may be assumed to play a role in the intercellular pathway. After a revision of different experiments from several authors (Wortmann et al, 1997) and further references therein, they suggested that there is, in fact, little evidence for the intercellular pathway, which identifies intercellular diffusion as the primary pathway for dyes into fibers. Instead the results support their view that under normal dyeing conditions, diffusion proceeds through the nonkeratinous components of the fiber according to a restricted transcellular diffusion mechanism.…”

“…According to Wortmann (Wortmann et al, 1997) and Swift (Swift, 1999) the main pathway for dye diffusion is through the nonkeratinous components (endocuticule, intermacrofibrillar matrix and nuclear remnant zones) according to a restricted transcellular diffusion mechanism. However, for Rippon (Rippon, 1999) and Leeder (Leeder, 1999), the intercellular cement is the pathway by which dye molecules reach cortical cells.…”