Mucoadhesive drug delivery systems: a promising noninvasive approach to bioavailability enhancement. Part II: formulation considerations

Highlights

• Mucoadhesive drug delivery systems (MDDS) are designed to adhere to specific mucosal tissue sites (such as GIT, nasal, oral, pulmonary, vaginal ophthalmic, and intravesical) in the body for local or systemic action. Diverse applications of MDDS have emerged in the past few decades, which have been detailed in the manuscript.

• Mucoadhesive polymers must have optimum moisture and surface energy to ensure proper wetting, swelling, and interpenetration into the mucus layer.

• Chitosan is a cationic polymer with excellent mucoadhesive properties explored in MDDS via different routes. It binds to mucin via hydrogen and ionic bonds.

• The degree of crosslinking, hydration, pH (charge on polymer), functional group, and molecular weight of the polymers dictates its mucoadhesive strength.

• Thiolated polymers bind to the mucin via disulfide bonds and have an exceptional binding affinity to the mucus layer, making them desirable polymer candidates for numerous drug delivery applications.

• Several recent MDDS demonstrate a combination of mucoadhesive polymers with other excipients such as permeation enhancers and hydrogels for versatile applications such as prolonged/controlled drug release or for improved drug absorption. These strategies are especially useful in the case of complications such as COVID-19.

• Advancement in nanotechnology has diversified MDDS applications even further. The confluence of unique size and surface morphology of nano systems with mucoadhesive polymers have improved mucoadhesion along with increased cellular uptake and drug absorption.

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