Mucoadhesive Drug Delivery Systems Sample Clauses

Mucoadhesive Drug Delivery Systems. Mucoadhesion is the attachment of any type of polymer to the mucus layer via strong interaction between the functional groups of the polymer and those of the mucosa lining of the tissue. The mucoadhesive bonding is attained mostly by physical, chemical and more importantly through H-bonding. Hence, the presence of hydroxyl, carboxyl and H-bond forming functional groups strongly contributes to the strength of mucoadhesion [58, 59]. The formation process of mucoadhesive bonds include 1) wetting and swelling of the polymers, 2) interpenetration of the mucoadhesion polymer chains and entanglement of the polymer and mucin chains, 3) interfacial interaction of functional groups, 4) formation of weak chemical bonds [60]. The use of mucoadhesive drug delivery systems results in a controlled drug release and attachment at a specific site of the body. Increasing the residence time of the drug delivery systems at the site of absorption in the body may result in prolonging their action. As the GI tract is covered by a mucus layer, the mucoadhesive drug delivery system must be able to attach to a specific site in order to be beneficial. Acrylic acid based polymers have been used extensively for mucoadhesive applications. Their strong bond strength in contact with tissues allows localization of the drug at the site of absorption, increasing residence time at the absorbing tissue and increasing drug bioavailability. Their responsive behaviour to different pH values allows the drug to be released at the desired site of the GI tract [58, 61, 62]. In order to increase mucus interpenetration, adhesion promoters such as polyethylene glycol (PEG) may be employed, which are not mucoadhesive but contribute to the adhesion process. Moreover, these tethered promoters may be grafted onto polymeric surfaces such that at the one end they are covalently attached to the polymer surface and the other end is free. These grafted chains are able to diffuse into the mucus layer and enhance the mucoadhesiveness of the system [63, 64]. Peppas et al. have done extensive studies on the design and the effect of network morphology of polyethylene glycol (PEG) tethered copolymers as novel mucoadhesive drug delivery systems [60]. They have suggested that the performance of the copolymer is due to the synergistic effect of both polymers: the backbone polymer providing the hydrogen bonds between the hydrogel and mucus layer as well as the adhesive promoter that contributes to the mucoadhesion by incr...