ABSTRACT
Adhesion can be dened as the bond produced by contact between a pressure-sensitive adhesive (PSA) and a surface (Jiménez-Castellanos et al., 1993). The American Society for Testing and Materials (1984) has dened it as the state in which two surfaces are held together by interfacial forces, which may consist of valence forces, interlocking action, or both. Good (1983) dened bioadhesion as the state in which two materials, at least one biological in nature, are held together for an extended period of time by interfacial forces. It is also dened as the ability of a material, synthetic
12.1 Theories of Bioadhesion ....................................................................................................... 311 12.1.1 Wetting Theory of Bioadhesion ................................................................................ 313 12.1.2 Electrostatic Theory of Bioadhesion ........................................................................ 314 12.1.3 Diffusion Theory of Bioadhesion ............................................................................. 314 12.1.4 Adsorption Theory of Bioadhesion .......................................................................... 315
12.2 Bioadhesive Materials ........................................................................................................... 316 12.3 Factors Affecting Bioadhesion ............................................................................................. 318
12.3.1 Hydrophilicity ........................................................................................................... 318 12.3.2 Molecular Weight ..................................................................................................... 318 12.3.3 Cross-Linking and Swelling ..................................................................................... 318 12.3.4 Spatial Conformation ................................................................................................ 318 12.3.5 pH ............................................................................................................................. 318 12.3.6 Concentration of Active Polymer.............................................................................. 319 12.3.7 Drug/Excipient Concentration .................................................................................. 319 12.3.8 Other Factors Affecting Bioadhesion ....................................................................... 319
12.4 Determination of Bioadhesive Force of Attachment ............................................................ 320 12.5 Characterization Methods for Bioadhesive Drug Delivery Systems .................................... 322 12.6 Bioadhesive Drug Delivery Systems .................................................................................... 323
12.6.1 Bioadhesive Devices for the Oral Cavity .................................................................. 323 12.6.2 Bioadhesive Devices for the GIT .............................................................................. 325 12.6.3 Bioadhesive Devices for Rectal Drug Delivery ........................................................ 327 12.6.4 Bioadhesive Devices for Cervical and Vulval Drug Delivery .................................. 329 12.6.5 Bioadhesive Devices for Vaginal Drug Delivery ...................................................... 329 12.6.6 Bioadhesive Devices for Nasal Drug Delivery ......................................................... 330 12.6.7 Bioadhesive Devices for Ocular Drug Delivery ....................................................... 331
12.7 Conclusion ............................................................................................................................ 332 References ...................................................................................................................................... 332
or biological, to adhere to a biological tissue for an extended period of time. In biological systems, three main types of bioadhesion can be distinguished:
Type 1: Adhesion between two biological phases, for example, cell fusion, platelet aggregation, wound healing, adhesion between a normal cell and a foreign substance or a pathological cell.
