Nanocarriers in Ungual Drug Delivery

Abstract

Ungual disorders can impact quality of life, with onychomycosis and nail psoriasis being the most prevalent disorders among the general population. In humans, the main functions of the nail apparatus comprise protection against trauma, improvement of tactile sensations, and allowing precision gripping. In order to perform such functions, the nail plate has a hard structure formed by dead keratinized corneocytes tightly bound to each other, giving the nail plate a "barrier-like" character. Due to this property of the nail plate, drug delivery to the region is hindered, making the treatment of ungual disorders difficult, either by systemic or topical drug administration. Many strategies have been developed in the last few decades in an attempt to increase the bioavailability of drugs in the nail. Interest in the employment of nanostructured drug delivery systems aiming to increase the bioavailability of drugs in the nail plate upon topical administration has increased. Moreover, the association of the nanotechnological approaches with other methods may be a beneficial strategy when aiming to increase drug permeation through the nail barrier. In this sense, the present review has the intention of presenting the panorama of the current technological development of nanostructured systems designed for the local treatment of ungual disorders. Through this extensive literature review, it was possible to recognize, among the studies, a lack of standardization regarding the methodology of nail permeation assessment, which imposes an obstacle to comparison.

Keywords: nail disorders; nanostructured systems; onychomycosis; psoriasis; ungual drug delivery.

Figure 1

Top (A) and lateral (B) views of the nail apparatus. Adapted from OpenStax College CC BY 3.0 (https://creativecommons.org/licenses/by/3.0).

Figure 2

Flowchart demonstrating the steps of literature survey in scientific databases.

Figure 3

Annual distribution of research articles concerning nanostructured systems designed for ungual drug delivery.

Figure 4

Nanostructured systems designed for the local treatment of ungual disorders.

Figure 5

Schematic diagram of the nail plate illustrating a possible permeation pathway for a drug incorporated in a nanocarrier, where passage may occur through pores formed by multifactorial mechanisms.