ABSTRACT

This chapter deals with the synthesis, characterization, and biomedical applications of micro- and nanoparticles based on pH- and temperature-sensitive polysaccharides as important tools for the controlled delivery of drugs. The particulate systems are prepared from native pH-sensitive polysaccharides, such as alginic acid, hyaluronic acid, pectin (carboxylic groups), and chitosan (amino groups). Remarkably, polysaccharides that do not contain these groups can become pH sensitive by chemical modifications of the abundant hydroxylic groups (carboxymethylation, succinoylation, and grafting of pH-sensitive polymers). Since native polysaccharides, by themselves, show very limited temperature sensitivity, the insertion of thermosensitive polymers into polysaccharides is described. The most important polymers that are able to induce thermosensitivity in polysaccharides are poly(N-isopropylacrylamide), poloxamer, polyvinylcaprolactam, and poly(l-lactide). The transformation of native and modified polysaccharides in micro- or nanoparticles by using numerous methods, such as suspension cross-linking, ionic gelation, self-assembly, dialysis and nanoprecipitation, solvent evaporation/removal, etc., are presented. These particulate carriers are able to transport high amounts of drugs to the desired place and release it at the appropriate rates when the pH and/or temperature changes.