page_title: Chitosan
section_title: Manufacture and properties
hierarchical_section_title: Chitosan / Manufacture and properties
caption_attribution_description: English: A heap of en:Pandalus borealis shrimp. Originally from en.wikipedia; description page is/was here. 2005-03-09 (original upload date) Original uploader was Stemonitis at en.wikipedia
context_page_description: Chitosan is a linear polysaccharide composed of randomly distributed β--linked D-glucosamine and N-acetyl-D-glucosamine. It is made by treating the chitin shells of shrimp and other crustaceans with an alkaline substance, such as sodium hydroxide.
  Chitosan has a number of commercial and possible biomedical uses. It can be used in agriculture as a seed treatment and biopesticide, helping plants to fight off fungal infections. In winemaking, it can be used as a fining agent, also helping to prevent spoilage. In industry, it can be used in a self-healing polyurethane paint coating. In medicine, it is useful in bandages to reduce bleeding and as an antibacterial agent; it can also be used to help deliver drugs through the skin.
context_section_description: Chitosan is produced commercially by deacetylation of chitin, which is the structural element in the exoskeleton of crustaceans (such as crabs and shrimp) and cell walls of fungi. The degree of deacetylation (%DD) can be determined by NMR spectroscopy, and the %DD in commercial chitosans ranges from 60 to 100%. On average, the molecular weight of commercially produced chitosan is 3800–20,000 daltons.  A common method for the synthesis of chitosan is the deacetylation of chitin using sodium hydroxide in excess as a reagent and water as a solvent.  The reaction follows first-order kinetics though it occurs in two steps; the activation energy barrier for the first stage is estimated at 48.8 kJ·mol⁻¹ at 25–120 °C and is higher than the barrier to the second stage.
  The amino group in chitosan has a pKₐ value of ~6.5, which leads to significant protonation in neutral solution, increasing with increased acidity (decreased pH) and the %DA-value. This makes chitosan water-soluble and a bioadhesive which readily binds to negatively charged surfaces such as mucosal membranes. Chitosan enhances the transport of polar drugs across epithelial surfaces, and is biocompatible and biodegradable. It is not approved by FDA for drug delivery though. Purified quantities of chitosans are available for biomedical applications.
  Nanofibrils have been made using chitin and chitosan.
caption: Commercial chitosan is derived from the shells of shrimp and other sea crustaceans, including Pandalus borealis, pictured here.[1]
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