Chapter 2 - Micro- and nanoscale drug delivery systems based on xanthan gum hydrogels

Abstract

Xanthan gum (XG) is a highly purified anionic polysaccharide produced by the bacteria Xanthomonas campestris during the aerobic fermentation of glucose, sucrose, or some complex substrates. It is a widely used, relatively inexpensive, nontoxic, biodegradable and bioadhesive pharmaceutical excipient. Moreover, the properties of XG in aqueous solutions, reflected in the stability of the ionized form in a wide range of pH, temperature, and concentration of dissolved salts, as well as the possibility of chemical modification (grafting), make it suitable for forming various biocompatible homopolymer and heteropolymer hydrogels based on physical interactions or chemical cross-linking. XG-based hydrogels are promising microscale and nanoscale carriers that can be administered as solid, semisolid, and liquid dosage forms by a variety of routes of administration, such as oral, (trans)dermal, parenteral, ocular, nasal, and rectal. Of particular importance is the combining of XG or corresponding chemical derivatives with other natural, semisynthetic, and synthetic polymers, to achieve optimal rheological and thermal properties, swelling capacity in aqueous media, pH-sensitivity, thermosensitivity, redox-sensitivity, and electrosensitivity of the hydrogel carriers, and thus to control and target drug delivery. Recent studies have demonstrated the possibility of obtaining nanocomposite hydrogels by forming hybrids of XG-based hydrogels and nanomaterials (nanoparticles, microemulsions, and nanoemulsions) that have shown superior stability and drug delivery performances compared to starting components. Selected examples of carriers based on XG hydrogels are commented on in this chapter, with special reference to their preparation/synthesis, physicochemical characteristics and capacity to deliver drugs with poor solubility, permeability through biological barriers, stability, and/or toxicological profile.