Ability of Hydroxypropyl Chitosan Nail Lacquer To Protect against Dermatophyte Nail Infection

Authors: M. A. Ghannoum, L. Long, N. Isham, A. Bulgheroni, M. Setaro, M. Caserini, R. Palmieri, and F. Mailland

Publication Year: 2015

PMID: 25547349

The treatment of onychomycosis has improved recently with the addition of novel topical agents used either alone or in combination with systemic oral drugs. However, recurrent or persistent infection occurs in up to 25% of patients (1). Several predisposing factors may contribute to a patient’s susceptibility to fungal nail infection, including age, impaired blood circulation, diabetes, physical trauma, occupation, and lifestyle (1,–6). The health of the nail itself may have an important bearing on the ability of the dermatophyte fungi to establish an infection, as most cases of onychomycosis are secondary to a previously established skin infection and/or nail trauma, derived either from mechanical insults or from exposure to chemical agents which can alter the natural nail barrier function. In this regard, the use of urea and/or isopropyl alcohol, chemicals often used in nail care to dissolve the nail keratin or to remove solutions from the nail surface, can undermine the nail structure and make it more prone to fungal infections.

A topical agent that strengthens the nail, improving the natural barrier to infection, might represent a valuable option for preventing new or recurrent fungal infections. The hydroxypropyl chitosan (HPCH)-based nail solution (Genadur) developed by Polichem is based on aminosaccharide chitin extracted from the crab carapace. The other two components, methyl sulfonyl methane and Equisetum arvense (an herbaceous perennial plant commonly known as horsetail), provide sulfur and silica, which contribute to the strengthening of the nail and which provide minerals to form the collagen that cements the nail cells. This water-based HPCH solution forms a protective film that remineralizes and restructures nails, protects keratin, and maintains hydration. In clinical studies, it has been shown to reduce the signs of fragility and roughness in the nails of patients with psoriatic nail dystrophy (7,–9). The HPCH-based nail solution is not intended as a cure for onychomycosis, as it does not exhibit antifungal activity; instead, it is able to form a film on the nail surface that may prevent fungal invasion. Moreover, the solution, being devoid of any pharmacological or toxicological effect, can be used indefinitely.

In this paper, we describe the effects of an HPCH-based nail solution compared to the effects of urea and isopropyl alcohol on hardness and on ultrastructure and tensile and flexural strength using bovine hooves, which have been validated as equivalent in structure to human nails (10). We used bovine hooves in this study because they are less expensive and more easily obtained than human cadaver nails. In addition, although the bovine keratin is chemically slightly different from that of humans, these differences were not believed to affect the results of the investigation. On the other hand, the great interindividual variability of human nails, e.g., due to sex, age, thickness, and length, may have affected the results. In our investigation, the bovine samples were cut to a standardized size and thickness for the various assays.

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