Nanocarriers for respiratory diseases treatment: recent advances and current challenges

Pulmonary delivery of locally-acting drugs encapsulated in nanocarriers provides several advantages for the treatment of respiratory diseases such as asthma, chronic obstructive pulmonary diseases, cystic fibrosis, tuberculosis and lung cancer. These advantages include, among others, sustained drug delivery to the lungs, reduced therapeutic dose and improved patient compliance. The aim of this review is to give an updated overview on recent advances recorded in the last few years in this field as well as on the major challenges still existing and that remain to be overcome before any clinical application. After an outline on the cellular and extracellular barriers affecting drug delivery to the airways both in physiological and pathological conditions, the significant developments recorded using inhaled polymeric- and lipid-based nanocarriers for drug and gene delivery to the lung are presented. In this discussion, the major challenges existing in the field are evidenced including the understanding of the factors governing the mucus penetration capability of these nanocarriers and the identification of new technologies for delivering drugs to specific regions or cell types of the lungs. In this regard, the recognition of receptor expressed only at lung level may facilitate drug targeting to this organ and it should improve the therapeutic efficacy of nanocarrier-based treatments for respiratory diseases.