Aqueous MEA and Ammonia Sorption-Induced Damage in Keratin Fibers

Abstract

The sorption of aqueous monoethanolamine (MEA) and ammonia solutions in keratin fibers and its subsequent effect on their mechanical performance has been investigated. The diffusion kinetics of MEA into keratin fibers for 0.1, 1.0, and 5 v/v % MEA in water at 30 and 50 °C were found to exhibit two clear regimes of absorption behavior: a linear Fickian diffusion regime for initial times up to 100 min, after which a second slower uptake process was observed. Single fiber tensile tests showed that the Young's modulus and the tensile failure stress for 5% MEA-treated fibers, compared to untreated fibers, were 25% lower after 1 h of treatment and 50% lower after 9 h of treatment. Aqueous treatments of 0.1 and 1% MEA, as well as 0.6 and 3% aqueous ammonia, had no measurable effect on either Young’s modulus or tensile failure stress for the fibers. Scanning electron microscopy images and protein content analysis confirmed that keratin fibers exposed to 5% MEA solution exhibited significant surface damage as well as high levels of protein loss. This study confirms for the first time the important damage hair treatments containing 5% aqueous MEA can cause on keratin fibers.

Bioinspired Chemoenzymatic Route to Artificial Melanin for Hair Pigmentation

“…Apart from preventing penetration into the hair cortex and minimizing inner hair perturbation, enzymatic reactions also limit damage to the outer hair layers as compared to the basic oxidative protocols. It is known that cuticle swelling under basic conditions can lead to potential hair damage or morphological changes of the hair surface. , Indeed, commercial dyes are designed to do this as part of the process of entraining dyes into hair fibers. To demonstrate how chemoenzymatic dyeing contrasts with this process, the hair samples were treated using either basic or enzymatic additives in the absence of the monomers, allowing us to investigate the outer hair morphology in the absence of any coating being formed.…”

“…We reasoned that if such a chemoenzymatic approach were exploited to deposit synthetic melanin onto hair fibers, it would provide not only a milder, but also a valuable alternative to previously described methods. − This approach offers four advantages over previously reported reaction conditions. First, it avoids the use of basic environments commonly used in hair dye formulations (e.g., ammonia and monoethanolamine). ,, Such basic conditions can cause skin irritation and damage hair cuticles, especially after repeated applications. , Second, its precursors are not as toxic as currently used hair dye chemicals, which include phenol derivatives, resorcinol, and paraphenylenediamine (PPD) . Third, chemoenzymatic oxidation allows the use of monomer substrates other than dopamine and its derivatives, including natural phenolamines, catecholamines, and amino acids, that are safe, scalable, and can give rise to a wider range of colors.…”

“…First, it avoids the use of basic environments commonly used in hair dye formulations (e.g., ammonia and monoethanolamine). 20,21,32 Such basic conditions can cause skin irritation and damage hair cuticles, especially after repeated applications. 32,33 Second, its precursors are not as toxic as currently used hair dye chemicals, which include phenol derivatives, resorcinol, and paraphenylenediamine (PPD).…”

“…20,21,32 Such basic conditions can cause skin irritation and damage hair cuticles, especially after repeated applications. 32,33 Second, its precursors are not as toxic as currently used hair dye chemicals, which include phenol derivatives, resorcinol, and paraphenylenediamine (PPD). 11 Third, chemoenzymatic oxidation allows the use of monomer substrates other than dopamine and its derivatives, including natural phenolamines, catecholamines, and amino acids, that are safe, scalable, and can give rise to a wider range of colors.…”

Colorful Pigments for Hair Dyeing Based on Enzymatic Oxidation of Tyrosine Derivatives

“…The optical microscopy and SEM images of the cross section of the hair dyed with tyrosine derivatives show that the nanoparticles are evenly coated on the surface of the hair without destroying the internal structure of the hair, highlighting the different dyeing mechanisms of enzymatic dyeing from other methods (Figure 7a,b). 58,59 The base materials used in conventional chemical hair dyes would cause swelling of the hair, which in turn causes the dye to penetrate deeply into the hair cortex to achieve coloration. For enzymatic reaction, no alkali and additional additives are used, and the enzymatic hair dyeing provided here successfully solves problems such as dryness and fragility caused by the conventional hair dyeing process, and can produce hair color without damaging the composition and structure of the internal hair.…”