Composite hydrogels of pectin and alginate

Abstract The biopolymers alginate and pectin are widely used in food, cosmetics, and medicine. These polysaccharides have received significant attention in recent years due to their natural availability and interesting properties such as nontoxicity, biodegradability, and biocompatibility. This chapter gives an overview about composite hydrogels of alginate and pectin and their applications in drug delivery and tissue engineering. The Ca-dependent gelation mechanisms are similar for alginate and pectin because their Ca-binding sites present a mirror symmetric conformation. The egg-box model can be applied for both biopolymers, but the structure and driving force are different. Several extrinsic (polymer concentration, temperature, pH) and intrinsic (molecular weight, percentage of guluronic acid/galacturonic acid, acetylation) factors can influence polysaccharide gelation and gel physicochemical properties. The association of these biopolymers were promising wall material for biomolecules or bacteria-controlled release. Several encapsulation techniques (extrusion/coextrusion, spray-drying, electrospinning) using alginate and pectin were developed to obtain particles (beads, microcapsules, fibers) from a millimetric to a nanometric scale. Size, morphology, and mechanical stability of the gel particles may vary depending on the nature of the polymeric matrix composition. An increase of polymer content and Ca2   + concentration leads, in particular, to a strengthening of the gel mechanical properties. Composite alginate-pectin gels present interesting applications in drug delivery and particularly in colon-specific drug delivery systems. Concerning the tissue engineering field, to the best of our knowledge, composite alginate-pectin hydrogels still remain little studied to this day.