Permanent hair dyeing is a popular process adopted by millions of people around the world, and involves complex oxidative reactions between precursor agents (aromatic amines) and couplers (phenolic compounds), in oxidizing alkaline medium, inside the hair strand. The p-toluenediamine (PTD) has been increasingly used in permanent hair dye compositions as precursor agent and it is associated with many adverse effects, such as allergies, dermatitis, skin infections, eye irritation, opacity of the corneas, stomach ulcers, aplastic anemia, and it is recognized for its high genotoxic, mutagenic and carcinogenic properties. However, little is known about the interaction mechanism of hair dyes with the capillary fiber. In this way, the investigation of the interaction of PTD with keratin is important since will enable in a better understanding of the physiological mechanisms of action and the side effects of hair dyes. The evaluation of the keratin interaction with PTD in incubated solutions, by differential pulse voltammetry and ultraviolet-visible spectroscopy, and in situ using a keratin-electrochemical biosensor, was investigated. The effect of the keratin-PTD interaction was electrochemically followed comparing the changes in the keratin electroactive amino acid residues oxidation peaks, in the absence and presence of the PTD. The interaction occurred in two ways. First, PTD interacts with keratin causing the condensation/aggregation of keratin, producing a rigid PTD-keratin complex structure, with a preferential interaction between the keratin amino acid residues carboxylic groups with PTD. Subsequently, the intercalation of PTD molecules in the keratin structure, cause greater exposure of the keratin amino acids residues at the GCE surface and, consequently, greater ease in oxidizing them. The peaks attributed to the keratin amino acid residues oxidation detected, suggest that, under the experimental conditions used, PTD induce keratin oxidative damage.

Keratin-electrochemical biosensor for in situ evaluation of human keratin interaction with hair dye precursor p-toluenediamine

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.