Micro- and nano-carrier systems: The non-invasive and painless local administration strategies for disease therapy in mucosal tissues

Mucus is a viscoelastic and adhesive obstacle which protects vaginas, eyes and other mucosal surfaces against foreign pathogens. Numerous diseases that affect the mucosa could be afforded prophylactic and therapeutic treatments with fewer systemic side effects if drugs and genes could be sufficiently delivered to the target mucosal tissues. But drugs and genes are trapped effectively like other pathogens and rapidly removed by mucus clearance mechanism. The emergence of micro- and nano-delivery technologies combined with the realization of non-invasive and painless administration routes brings new hope for the treatment of disease. For retained drugs and genes to mucosal tissues, carriers must increase retention time in the mucus to make full contact with epithelial cells and be transported to target tissues. This review focuses on the current development of micro- and nano-carriers to improve the localized therapeutic efficiency of targeted and sustained drug and gene delivery in mucosal tissues.