Nail keratin and nail-plate structural matrix

The nail keratin and nail-plate structural matrix represent the primary structural and protective component of the human nail, consisting of a dense network of hard alpha-keratins and keratin-associated proteins (KAPs). This matrix is characterized by extensive disulfide cross-linking, which provides the nail with its characteristic hardness and resistance to environmental stressors. In clinical pharmacology, this structure serves as both a formidable barrier to drug penetration and a reservoir for certain lipophilic and keratinophilic drugs, such as terbinafine and itraconazole. The high affinity of these agents for nail keratin allows for the formation of a drug depot, maintaining therapeutic levels long after treatment has ended. However, the dense matrix also limits the efficacy of many topical treatments, necessitating the use of chemical enhancers like urea to increase permeability. Pathological changes in the matrix are central to conditions like onychomycosis, where fungal pathogens degrade keratin, and nail psoriasis, which alters the matrix's structural integrity. Consequently, the nail-plate structural matrix is a key focus for developing advanced transungual drug delivery systems and restorative nail therapies.

Other names

Nail plateUngual keratinHard keratinNail matrix structural componentNail plate matrix

Drugs interact with the nail keratin and matrix through binding (sequestration), passive diffusion (penetration), or chemical modification (keratolysis and cross-linking). Antifungals often bind to keratin to form a therapeutic depot, while penetration enhancers disrupt the matrix's disulfide bonds and lipid layers to facilitate drug delivery to the underlying nail bed. Newer antifungals like efinaconazole and tavaborole are designed with low keratin affinity to maximize the concentration of free, active drug that can permeate through the matrix to reach the site of infection.