Bioadhesive polymer

A number of the water-soluble polymers also have adhesive properties which are being extensively evaluated for drug delivery (9). These polymers will adhere to the mucous coating in the gastrointestinal tract, the nose, and the mouth to delay passage and sustain drug release. Those polymers with the best adhesive properties are those with hydroxyl and carboxyl groups. Table II lists some of the bioadhesive polymers and their adhesive properties. 

HW Hui, JR Robinson. (1985). Ocular delivery of progesterone using a bioadhesive polymer. Int J Pharm 26 203-213. 

In the gastrointestinal tract, a mucoadhesive drug delivery system provides advantages in prolonging the residence time of devices. The use of pH-sensitive bioadhesive polymers has been proposed [26], An extensive review of pH-sensi-tive hydrogels is given by Brpndsted and Kopecek [27],... 

Interpenetration of the bioadhesive polymer chains and entanglement of polymer and muein ehains, and... 

Park, K., and Robinson, J.R., Bioadhesive polymers as platforms for oral controlled drug delivery method to study bioadhesion, Int. J. Pharm., 19 107-127 (1984). 

Zhou, M.P., and Donovan, M.D., Intranasal mucociliary clearance of putative bioadhesive polymer gels, Int J. Pharm., 135 115-125 (1996). 

Robinson, J.R., and Bologna, W. J., Vaginal and reproductive-system treatments using bioadhesive polymer, J. Control. Rel, 28 87-94 (1994). 

In vivo methods, which are few, measure the residence time of bioadhesives at the application site [47]. Techniques like y-scintigraphy, the perfused intestinal loop and radiolabeled transit studies using Cr-labeled bioadhesive polymer [48] and Tc-labeled polycarbophil [49] have been employed for this purpose. 

A novel concept of using bioadhesive polymers as enzyme inhibitors has been developed [97]. Included are derivatives of poly acrylic acid, polycarbophil, and car-bomer to protect therapeutically important proteins and peptides from proteolytic activity of enzymes, endopeptidases (trypsin and a-chymotrypsin), exopeptidases (carboxypeptidases A and B), and microsomal and cytosolic leucine aminopeptidase. However, cysteine protease (pyroglutamyl aminopeptidase) is not inhibited by polycarbophil and carbomer [97]. 

The mucin to which bioadhesive polymers adhere is secreted by columnar epithelial cells and is a network comprising 0.5-2% of highly-hydrated flexible glycoprotein chains [400], which contain negatively charged moieties, and are... 

A host of bioadhesive controlled release systems have been proposed in recent years. Among the most commonly studied applications of bioadhesive materials is the area of buccal controlled delivery [408], The buccal delivery of small peptides from bioadhesive polymers was studied by Bodde and coworkers [409], and a wide range of compositions based on poly(butyl acrylate) and/or poly(acrylic acid) gave satisfactory performance. Bioadhesive poly(acrylic add)-based formulations have also been used for oral applications [402,410] for the sustained delivery of chlorothiazide [410] and for a thin bioadhesive patch for treatment of gingivitis and periodontal disease [411]. Other bioadhesive applications of polyelectrolytes include materials for ophthalmic vehicles [412,413], and systems for oral [410,414,415-419], rectal [420,421] vaginal [422] and nasal [423] drug delivery. 

The main reason that poly(acrylic acid) and poly(methacrylic acid) hydrogels and hydrogel particles have been utilized in oral drug delivery is the fact that they also possess bioadhesive properties (Park and Robinson 1987). Bioadhesive polymers... 

Longer, M.A., H.S. Ch ng, and J.R. Robinson, 1985. Bioadhesive polymers as platforms for oral controlled drug delivery III oral delivery of chlorothiazide using a bioadhesive polymer. J Pharm Sci 74 406. 

Junginger, H.E. 1990. Bioadhesive polymer systems for peptide delivery. Acta Pharm Technol 36 110. 

Kaelble, D.H. 1977. A surface energy analysis of bioadhesion. Polymer 18 475. 

Bioadhesive formulations and microsphere delivery systems in particular have attracted much attention. As drug formulations are usually rapidly removed from the site of deposition by the mucociliary clearance, increasing the retention time of drug in the nasal cavity via bioadhesion can increase bioavailability [28], Bioadhesion may be defined as the ability of a material (synthetic or biological) to adhere to a biological tissue for an extended period of time. When applied to a mucous membrane, a bioadhesive polymer may adhere primarily to the mucus layer or epithelial cell surface in a phenomenon known as mucoadhesion [29,30]. The bioadhesive properties of a wide range of materials have been evaluated over the last decade. 

Is a local or systemic effect required This will influence, for example, the choice between a traditional dosage form, such as a semisolid cream or gel, and a system that promotes increased intravaginal residence, with a concomitant increased possibility of absorption across vaginal epithelium, for example, from intravaginal ring (IVR) systems or systems utilizing a bioadhesive polymer component. 

The notion that bioadhesion enhances the efficiency of drug delivery through an intimate and prolonged contact between the delivery device and the absorption site has resulted in considerable efforts to develop and evaluate bioadhesive polymers. The use of bioadhesive polymers in controlled release drug delivery systems provides potential advantages, including... 

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