Chitosan Chemistry

Understanding Chitosan Chemistry

At one time or another, you’ve probably sat down to dinner with oysters, lobsters, shrimps, crabs, squid, prawns, or clams on the table. You’ve probably feasted on these appetite boosters unless you’re allergic to crustaceans. Well, the next time you partake on this event, think twice before you throw away the outer shell. The shell actually contains chitosan, a very valuable polymer.

Speaking of chitosan, it is interesting to know that this substance is a biopolymer that has a wide range of biomedical applications, such as wound healing, tissue engineering and tissue repair, as well as local delivery of cells, drugs, proteins, genes and other therapeutic. You will encounter these biomedical applications of chitosan every time you discuss about the chitosan chemistry.

The Production of Chitosan

According to some chitosan chemistry resources, chitosan is formed through N-deacylation of the chitin molecule. Note that chitosan is a linear polysaccharide composed of randomly distributed B-(1®4)-linked D-glucosamine (deacetylated unit; D) and N-acetyl-D-glucosamine (acetylated unit; A). With this composition, chitosan is produced commercially by deacetylation of chitin, which according to chitosan chemistry resources is the structural element in the exoskeleton of crustaceans. The degree of deacetylation (%DA) can then be identified by NMR spectroscopy, and the %DA in commercial chitosan is in the range of 60 to 100 percent.

Chemical Properties of Chitosan

Several biomedical studies showed that chitosan is useful as polymer carrier for catalysts as well as for intermediate products for synthesis of fine chemicals. As noted by a number of chitosan chemistry resources, chitosan has its own chemical properties. These include:

Linear polyamine (poly-D-glucosamine)

Reactive amino groups

Chelates many transitional metal ions

Basteriostatic and fungistatic effect

Separations of protein

It is further worth noting that the viscosity of chitosan solution, based on chitosan chemistry studies, primarily depend on the average molecular weight of the polymer. This weight can be determined by size exclusion chromatography coupled with light scattering detection.

The Amino Group in Chitosan

Several chitosan chemistry studies have revealed that chitosan primarily contains amino group. This group has a pKa value of ~6.5, which means that chitosan is positively charged and soluble in acidic to neutral solution with a charge density dependent on pH as well as %DA-value.

Given such fact, chitosan chemistry studies then concluded that chitosan is no doubt a bioadhesive and readily binds to negatively charged surfaces like the mucosal membranes. Aside from this, chitosan chemistry resources that chitosan has the ability to improve the transport of polar drugs across the epithelial surfaces. With that, chitosan is found biocompatible and biodegradable.

Application of Chitosan

Following a number of successful chitosan chemistry studies, the development of commercial applications for chitin and chitosan has expanded rapidly in recent years. Much to that, there is now a great potential for exploitation of chitosan in numerous markets. Perhaps the best promises for these markets are benefits for the fields of health care, cosmetics, agriculture, waste and water treatment, food and beverages, immobilization and cell culture, and in the product separation and recovery.

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