Essential oils are natural products with a complex composition. Terpenes are the most common class of chemical compounds present in essential oils. Terpenes and the essential oils containing them are widely used and investigated by their pharmacological properties and permeation-enhancing ability. However, many terpenes and essential oils are sensitive to environmental conditions, undergoing volatilization and chemical degradation. In order to overcome the chemical instability of some isolated terpenes and essential oils, the encapsulation of these compounds in nanostructured systems (polymeric, lipidic, or molecular complexes) has been employed. In addition, nanoencapsulation can be of interest for pharmaceutical applications due to its capacity to improve the bioavailability and allow the controlled release of drugs. Topical drug administration is a convenient and non-invasive administration route for both local and systemic drug delivery. The present review focuses on describing the current status of research concerning nanostructured delivery systems containing isolated terpenes and/or essential oils designed for topical administration and on discussing the use of terpenes and essential oils either for their biological activities or as permeation enhancers in pharmaceutic formulations.

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.

Glioblastoma remains the most aggressive primary malignant tumor of the central nervous system, while the poor aqueous solubility of 3-O-methylquercetin (3OMQ) limits its pharmaceutical development despite its promising antiglioma activity. This study aimed to develop a novel nasal delivery system for 3OMQ by complexation with hydroxypropyl-β-cyclodextrin (HPβCD), followed by the development and evaluation of nasal formulations. Purified 3OMQ isolated from Achyrocline satureioides (Lam.) DC was complexed with HPβCD and incorporated into hydroxypropyl methylcellulose (HPMC) or poloxamer 407 formulations. Selective antiglioma activity of the selected formulation and the 3OMQ/HPβCD complex was evaluated in vitro in C6 glioma, HaCaT keratinocyte, and primary astrocyte cultures. The isolated 3OMQ showed purity above 97%, while complexation increased its apparent aqueous solubility 39-fold. Ex vivo permeation studies using porcine nasal mucosa demonstrated that the HPMC formulation provided higher nasal permeation and tissue retention than the poloxamer system, while preserving favorable release characteristics. Furthermore, both the 3OMQ/HPβCD complex and the HPMC formulation exhibited selective cytotoxicity toward C6 glioma cells while preserving the viability of primary astrocytes and HaCaT cells. These findings support the HPMC-based 3OMQ/HPβCD system as a promising nasal delivery platform with potential for further development as a nose-to-brain strategy for antiglioma therapy.