Manufacture and properties Chitosan

forming chitosan partial deacetylation of chitin



commercial chitosan derived shells of shrimp , other sea crustaceans, including pandalus borealis, pictured here.

chitosan produced commercially deacetylation of chitin, structural element in exoskeleton of crustaceans (such crabs , shrimp) , cell walls of fungi. degree of deacetylation (%dd) can determined nmr spectroscopy, , the %dd in commercial chitosans ranges 60 100%. on average, molecular weight of commercially produced chitosan between 3800 , 20,000 daltons. common method synthesis of chitosan deacetylation of chitin using sodium hydroxide in excess reagent , water solvent. reaction occurs in 2 stages under first-order kinetic control. activation energy first step higher second; value estimated 48.76 kj/mol @ 25–120 °c. reaction pathway, when allowed go completion (complete deacetylation) yields 98% product.

the amino group in chitosan has pka value of ~6.5, leads protonation in acidic neutral solution charge density dependent on ph , the %da-value. makes chitosan water-soluble , bioadhesive readily binds negatively charged surfaces such mucosal membranes. chitosan enhances transport of polar drugs across epithelial surfaces, , biocompatible , biodegradable. not approved fda drug delivery though. purified quantities of chitosans available biomedical applications.

chitosan , derivatives, such trimethylchitosan (where amino group has been trimethylated), have been used in nonviral gene delivery. trimethylchitosan, or quaternised chitosan, has been shown transfect breast cancer cells, increased degree of trimethylation increasing cytotoxicity; @ approximately 50% trimethylation, derivative efficient @ gene delivery. oligomeric derivatives (3–6 kda) relatively nontoxic , have gene delivery properties.