Thiolated Polymers: Pharmaceutical Tool in Nasal Drug Delivery of Proteins and Peptides

Although bioavailability of peptides administered through nasal route is still under 1% because of low membrane permeability, a short local residence time and a high metabolic turnover in the nasal epithelium but the richly supplied vascular nature of the nasal mucosa coupled with its high drug permeation makes the nasal route of administration attractive for many drugs including proteins and peptides. Thiolated polymers (thiomers) which are also recognized as mucoadhesive polymers, discovered so far, attach itself to mucus membrane by covalent and non-covalent binding such as electrostatic forces and physical mechanism. These new generation polymers are capable of forming covalent bonds. Thiomers are of two types firstly anionic thiolated polymers having carboxylic acid groups as anionic substructures and cationic thiomers are mainly based on chitosan. Thiomers are hydrophilic molecules exhibiting free thiol groups responsible for numerous qualities of well-established polymeric excipients such as poly(acrylic acid) and chitosan. Thiomers possess cohesive, mucoadhesive, enzyme inhibitory and permeation enhancing properties. Thiomers based microparticles, microspheres, nanoparticles and gels for nasal drug delivery systems have shown promosing potential. Thiomers matrix-tablets are found to be stable under all storage conditions. On the basis of various properties, thiomers represent a promising new generation of multifunctional polymer for protein delivery through nasal route.