Synthetic melanin as a bioinspired antioxidant: Modulating oxidative stress from 2D skin models to human skin...

Oxidative stress is a central pathogenic mechanism in a wide range of dermatological and inflammatory disorders, driving DNA damage, impaired epidermal barrier function and defective tissue repair. Although endogenous melanin provides intrinsic redox protection in skin, its therapeutic translation has been limited by poor solubility, structural heterogeneity and insufficient mechanistic validation in human tissues.

To determine whether commercially available synthetic melanin is internalised by human keratinocytes and confers intracellular protection against oxidative injury, with functional and molecular validation in ex vivo human skin.

Keratinocyte-based assays were integrated with ex vivo human skin explants to evaluate the effects of synthetic melanin (1-6 µM) under chemically induced oxidative stress (100 µM tert-butyl hydroperoxide). Intracellular reactive oxygen species (ROS), phosphorylated histone H2AX (γ-H2AX) associated DNA damage, keratinocyte migration, tight-junction organisation and epithelial permeability were assessed in vitro. Label-free Raman spectroscopy was employed to map oxidative biochemical perturbations and molecular recovery in human skin tissue.

Synthetic melanin was efficiently internalised by human keratinocytes in a dose-dependent and well-tolerated manner, functioning as an intracellular redox modulator. Melanin pre-treatment significantly reduced intracellular ROS accumulation and attenuated oxidative DNA damage, improved keratinocyte migration, preserved tight-junction organisation and maintained epithelial barrier integrity under oxidative stress. In human skin explants, oxidative injury caused marked attenuation of Raman spectral signatures associated with proteins, lipids, and aromatic amino acids. Melanin treatment restored these biochemical features, reduced DNA damage-associated spectral bands and preserved epidermal biochemical architecture.

Synthetic melanin functions as a bioinspired intracellular redox active compound that mitigates oxidative stress induced damage at cellular and tissue levels. By combining mechanistic in vitro assays with label-free molecular validation in human skin, this study provides proof-of-concept evidence supporting further translational investigation of synthetic melanin in oxidative stress associated dermatological conditions.