Lipid-based colloidal systems (nanoparticles, microemulsions) for drug delivery to the skin: materials and end-product formulations

Abstract

Drug delivery to or via the skin presents both unique opportunities and obstacles due to skin structure, physiology, and barrier properties. The skin, the largest organ of the body, may be viewed either as a natural protective barrier against penetration of toxic exogenous compounds, excessive loss of water and other essential compounds, or as a promising portal of entry for drugs for local and/or systemic action. Many novel lipid nanocarriers have been designed for topical application of drugs since they allow these molecules to overcome the skin barrier and improve cutaneous bioavailability. The increased drug absorption is often a consequence of a reversibly disrupted barrier function of the skin by the vehicle itself or by specific ingredients figuring in the topical formulation that act as penetration enhancer. Micro/nanoemulsions and lipid nanoparticles are known to provide several advantages over conventional formulations in terms of stability and skin penetration enhancement. However, their characteristics in the original form are low viscous liquids and colloidal dispersions. Therefore, their topical application may be limited in some cases. This review describes recent works in formulating lipid nanocarriers, especially in the semi-solids and hydrogels forms, and reports their special features for biomedical and dermocosmetic applications.