The carrier technology provides an intelligent approach for drug delivery by entrapping the
drug into a carrier, such as nanoparticles, microspheres, hydrogels, and so on, which can increase the
bioavailability of drug, enhance targeting, reduce toxicity and side effects of drug. The polysaccharides,
e.g., chitosan and its derivatives, as carriers for delivery of chemical drugs and genes or proteins
were summed up herein.