Polymers bioadhesivity

Deacon MP (1999) Polymer Bioadhesives for Drug Delivery. PhD Thesis, University of Nottingham, Nottingham, UK... 

Peppas, N.A., and Buri, P., Surface, interfacial and molecular aspects of polymer bioadhesion on soft tissue, J. Control. Rel., 2 257-275 (1985). 

In summary, the following points are to be stressed which should be accounted for when developing polymer bioadhesives ... 

Hassan, E.E., and J.M. Gallo. 1990. A simple rheological method for the in vitro assessment of mucin-polymer bioadhesive bond strength. Pharm Res 7 491. 

Mucoadhesive Polymers Bioadhesion refers to the attachment of a drug molecule or a delivery system to a specific biological tissue by means of interfacial forces. If the surface of the tissue is covered by a mucin film, as is the case for the external globe, it is more commonly referred to as mucoadhesion. 

FIGURE 52.3 Representation of the cross-linked structure of the mucin network. (1) Possible cross-linking can occur through entanglements, (2) molecular associations, and (3) permanent covalent cross-links. On average, the end-to-end distance between two junctions, r, corresponds to a particular molecular weight. My (Reprinted from J. Contr. Release, 2, Peppas, N.A. and Buri, P.A., Surface, interfacial and molecular aspects of polymer bioadhesion on soft tissues, 257-275. Copyright 1985, with permission from Elsevier.)... 

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. 

Table II. Examples of Polymers with Bioadhesive Properties...

Another approach is that of bioadhesive materials. The principle is to administer a device with adhesive polymers having an affinity for the gastric surface, most probably the mucin coat [12]. Bioadhesives have demonstrated utility in the mouth, eye, and vagina, with a number of commercially available products. To date, use of bioadhesives in oral drug delivery is a theoretical possibility, but no promising leads have been published. 

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],... 

Matthew V. Tirrell (Co-Chair) is Dean of the College of Engineering at the University of California at Santa Barbara. He was previously Professor and Head of the Department of Chemical Engineering and Materials Science at the University of Minnesota, where he served as Director of its Biomedical Engineering Institute. He received a B.S. from Northwestern University and a Ph.D. from University of Massachusetts. His interests are in transport and interfacial properties of polymers, with particular emphasis on molecular-scale mechanical measurements, bioadhesion, and new materials development. He is a member of the National Academy of Engineering. 

An interesting feature of current commercial products is that the polymer vehicles available for formulation have been limited to nonionic and anionic materials. The delivery vehicles available included off-the-shelf polymers such as carboxymethylcellulose, soluble starch, hydroxyethyl-cellulose, polyvinyl alcohol, poly(acrylic acid), and polyvinylpyrrolidone, or mixtures thereof. The choice of available polymeric delivery system primarily depends on component compatibility, aesthetics, and efficacy. However, by reliance upon available (off-the-shelf) systems, limitations on bioadhesion, drug bioavailability, contraceptive efficacy, and end-use characteristics has been limited. 

Bioadhesion to the vaginal substrate implies knowledge and demonstration of the mechanism of interaction. In the present case, mucoadhesion, bioadhesion, and substantivity can be used interchangeably when evaluating the mucosa as a substrate. Several forces may be active, such as electrostatic, hydrophobic, and hydrogen bonding, giving rise to surface interactions between the polymer and the mucosal substrate or diffusion into the mucus layer [48,49]. 

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

The diffusion theory states that interpenetration and entanglement of polymer chains are additionally responsible for bioadhesion. The intimate contact of the two substrates is essential for diffusion to occur, that is, the driving force for the interdiffusion is the concentration gradient across the interface. The penetration of polymer chains into the mucus network, and vice versa, is dependent on concentration gradients and diffusion coefficients. It is believed that for an effective adhesion bond the interpenetration of the polymer chain should be in the range of 0.2-0.5 pm. It is possible to estimate the penetration depth (/) by Eq. (5),... 

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). 

Chickering, D.E.lll, Jacob, J.S., and Mathiowitz, E., Bioadhesive microspheres. 2. Characterization and evaluation of bioadhesion involving hard, bioerodible polymers and soft tissue. Reactive Polymers, 25 189-206 (1995). 

Caramella, C M., Rossi, S., and Bonferoni, M.C., A Rheological Approach to Explain the Mucoadhesive Behavior of Polymer Hydrogels. In Bioadhesive Drug Delivery Systems (E. Mathiowitz, D.E. Chickering, III, and C.-M. Lehr, eds.), Marcel Dekker, Inc., New York, 1999, pp. 25-65. 

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). 

The term bioadhesion ean be defined as the ability of a material (synthetic or natural) to stick (adhere) to a biological tissue for extended periods of time [27]. The phenomenon of bioadhesion can be visualized as a two-step process. The first step involves the initial contaet between polymer and the biological tissue. The second step is the formation of seeondary bonds due to noncovalent interactions. The strength of bioadhesion (expressed as the foree of detachment) for a novel oligosaccharide gum Hakea Gibbosa) contained in a buccal tablet developed by Alur et al. [28,29]... 

A variety of polymers including water-soluble and insoluble, ionic and nonionic hydrocolloids, and water-insoluble hydrogels can be used in bioadhesive systems [31]. The bioadhesive properties of the polymer are affected by the ... 

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