CONVENTIONAL AND EMERGING MUCOADHESIVE POLYMERS FOR DRUG DELIVERY SYSTEMS: BIOADHESIVE PROPERTIES, STRUCTURAL CHARACTERISTICS, AND PHARMACEUTICAL APPLICATIONS

Mucoadhesive drug delivery systems represent an advanced strategy in pharmaceutical formulation design, utilizing polymers that enable prolonged contact between the drug delivery system and mucosal surfaces. The term mucoadhesion refers to the ability of a formulation containing a suitable natural or synthetic polymer to adhere to mucus layers or epithelial tissues. These systems have gained considerable attention owing to the high permeability and extensive vascularization of mucosal membranes, which facilitate rapid drug absorption into systemic circulation. Certain mucoadhesive routes such as buccal and nasal delivery may partially avoid hepatic first-pass metabolism and improve bioavailability depending on the physicochemical characteristics of the drug and the site of administration. Mucoadhesive polymers are employed in a wide range of pharmaceutical dosage forms, including tablets, gels, patches, powders, films, tapes, and semisolid preparations, to enable both local and systemic drug delivery through various mucosal routes. Polymers such as polyethylene glycol, hydroxypropyl methylcellulose, sodium alginate, sodium carboxymethylcellulose, guar gum, tragacanth, acacia, and related cellulose derivatives have been extensively explored due to their strong mucoadhesive potential. An ideal mucoadhesive polymeric system should exhibit rapid adhesion to the mucosal surface, maintain structural integrity without altering the physicochemical properties of the formulation, and allow controlled drug release. In addition, such polymers should be biodegradable, non-toxic, and capable of enhancing drug permeation while minimizing enzymatic degradation at the site of administration. The present review aims to provide a comprehensive overview of novel and emerging mucoadhesive polymers, with emphasis on their bioadhesive characteristics, structural features, mechanisms of adhesion, and applications in modern drug delivery systems.