Ability of hydroxypropyl chitosan nail lacquer to protect against dermatophyte nail infection

The development of a topical agent that would strengthen the nail, improve the natural barrier, and provide better drug penetration to the nail bed is needed. In this study, we examined the effects of a hydroxypropyl chitosan (HPCH)-based nail solution using a bovine hoof model. Following application of the nail solution, changes in the hardness of the hoof samples were measured using the Vickers method. Tensile and flexural strengths were tested by stretching or punching the samples, respectively. The ultrastructure was examined using scanning electron microscopy (SEM), and samples stained with periodic acid-Schiff (PAS) stain were used to determine the fungal penetration depth. The comparators included 40% urea and 70% isopropyl alcohol solutions. The HPCH nail solution increased hoof sample hardness in comparison to the untreated control sample (mean, 22.3 versus 19.4 Vickers pyramid number [HV]). Similarly, the HPCH solution increased the tensile strength (mean, 33.07 versus 28.42 MPa) and flexural strength (mean, 183.79 versus 181.20 MPa) compared to the untreated control. In contrast, the comparators had adverse effects on hardness and strength. SEM showed that the HPCH solution reduced the area of sample crumbling following abrasion compared to the untreated control (7,418 versus 17,843 pixels), and the PAS-stained images showed that the HPCH solution reduced penetration of the dermatophyte hyphae (e.g., penetration by Trichophyton mentagrophytes was <25 μm at day 9 versus 275 μm in the untreated control). Unlike chemicals normally used in cosmetic treatments, repeated application of the HPCH nail solution may help prevent the establishment of new or recurring fungal nail infection.