Similarly, keratin, gelatin, chitosan and alginate demonstrate excellent biocompatibility and bioactivity in scaffolds. Common synthetic polymeric nanoparticles include polyacrylamide, polyacrylate, and chitosan. Examples include chitosan, hyaluronic acid, and dextran. One difference between chitin and chitosan is that chitosan is soluble in acidic aqueous solutions. This copolymer of chitin and chitosan is a random or block copolymer. Chemically, chitin is closely related to chitosan (a more water-soluble derivative of chitin). Cationic polymers such as chitosan promote cell adhesion. Degraded molecules of chitin/chitosan exist in soil and water. Nanofibrils have been made using chitin and chitosan. Glucosamine is part of the structure of the polysaccharides, chitosan, and chitin. It instead exists as a copolymer with chitin's deacetylated derivative, chitosan. The chitosan salts are biocompatible and biodegradable making them useful as absorbable haemostats. Processes to size and strengthen paper employ chitin and chitosan. After this the chitosan polymer chain forms micro fibrils. The composite formed by carbon nanotubes and chitosan greatly improves the toughness of chitosan.