ABSTRACT
Bioadhesion is defined as the binding of a natural or synthetic polymer material to a biological substrate. Over the past few decades, bioadhesive-based drug delivery systems have received a great deal of attention. Bioadhesive dosage forms are primarily designed to attach and enable prolonged retention at the site of application, thus providing a controlled rate of drug release for improved therapeutic outcome. Most commonly these dosage forms are applied to the mucosal tissues of the body such as buccal, nasal, ocular, gastro, vaginal, and rectal mucosa. This mode of localized and/or systemic drug delivery will provide improved therapeutic benefits unlike other routes of drug delivery. For example, application of dosage forms to mucosal surfaces may be of benefit to drug molecules that are not amenable to the oral route, such as those that undergo acid degradation or extensive first-
pass metabolism. The mucoadhesive ability of a dosage form is dependent upon a variety of factors, including the nature of the mucosal tissue and the physicochemical properties of the polymeric formulation. The bioadhesive-based drug delivery systems can be formulated into different pharmaceutical dosage forms namely as gels, ointments, tablets, patches, films, and microspheres. It is, therefore, essential that these formulations bond/attach to the mucosal surface for prolonged time to provide efficient drug delivery. Formulation scientist have designed and tested a range of techniques and set-ups that are now commonly used to select candidate bioadhesive drug delivery platforms. This Chapter provides an overview of the various in vitro, ex vivo and in vivo techniques that have been extensively used in the characterization of bio-/mucoadhesion drug delivery systems. 2.1 Introduction
The primary aim of a bioadhesive-based drug delivery system is to prolong the residence time at the site of application. Prolonged residence time is advantageous since it will provide effective local drug delivery at the site of application for long-term. Bioadhesivebased drug delivery systems are available in a wide range of pharmaceutical dosage forms such as gels, creams, tablets, patches, and films. Depending upon the type of dosage form different routes such as oral, rectal, vaginal, gastrointestinal tract, ocular or nasal are used to deliver bioadhesive-based delivery system. Consequently, it is essential to characterize polymers bioadhesive property to a given biological tissue samples or its substitute. Characterizing provides vital information during pre-formulation development process, which will enable formulation scientists to select a suitable bioadhesive dosage form for drug delivery applications. Therefore, in this Chapter, we have discussed various set-ups that are commonly used in in vitro and in vivo characterizing of bioadhesive-based polymeric drug delivery systems. Importantly, we have discussed a vast number of in vitro techniques that are most commonly used in the pre-formulation characterization of a bio-/mucoadhesive drug delivery system.
