Liquid-crystalline membrane permeation ability for selected nitro hair dyes

Aim A comparison of permeation ability of selected semi‐permanent hair dyes and an attempt to estimate the influence of fundamental physicochemical parameters on dyes’ epidermal penetration rate. Methods Dyes’ permeation ability through liposome membrane (as a model of stratum corneum) with side‐by‐side cells was assessed. Results It has been shown that the chosen dyes are capable of permeating the membrane. High penetration coefficients (Kp) were obtained for a simple nitrophenylenediamines and nitroaminophenols. Their N‐, O‐hydroxyalkyl substitution significantly limits penetration. H‐bonding capability has a major impact on the investigated dyes’ permeation ability. Substituents with H‐bonding properties can significantly limit dyes’ penetration, even in the case of lipophilic structures. Special attention should be placed into compounds with strong intramolecular H‐bonding properties, which improve transmembrane transport. Conclusion Substitution patterns have an influence on selected nitro dyes’ permeation through a model stratum corneum. Permeation is limited by dyes diffusive properties (mostly by its H‐bonding properties). Hydroxyalkylation results in hindered dyes permeation: purple, violet and blue nitrophenylenediamine or nitroaminophenol derivatives are less permeable than its not substituted analogues.