Chitosan is a cationic polysaccharide derived from the partial deacetylation of chitin, exhibiting unique solubility in acidic conditions and versatile biological activities.
Chemical Structure
Chitosan comprises β-(1→4)-linked D-glucosamine (deacetylated units) and N-acetyl-D-glucosamine residues, with the degree of deacetylation (DD, typically 60–95%) determining free amino (-NH₂) groups at C2, alongside hydroxyls at C3 and C6. These functional groups enable protonation in acidic media (pKa ≈6.5), forming soluble polyelectrolytes, while hydrogen bonding confers semicrystalline structure and insolubility at neutral pH. Molecular weight varies widely (50–2000 kDa), influencing viscosity and reactivity.
Production and Properties
Obtained via alkaline hydrolysis of chitin from crustacean shells or fungi, chitosan features biocompatibility, biodegradability by lysozymes, antimicrobial action via membrane disruption, and chelation of metals. It forms films, gels, and nanoparticles, with properties tunable by quaternization or grafting. Low immunogenicity supports biomedical use, though batch variability affects consistency.
Health Benefits
Chitosan binds dietary lipids and cholesterol in the gut, reducing absorption for weight management and hyperlipidemia, while modulating microbiota and inflammation. It accelerates wound healing through hemostasis and angiogenesis, and shows promise in drug delivery for sustained release. Preclinical data indicate antioxidant and antitumor effects, though human trials require standardization.
Applications and Limitations
Widely used in tissue engineering scaffolds, antimicrobial coatings, and agriculture as elicitors, chitosan's market spans cosmetics to wastewater treatment. Challenges include pH-limited solubility, variable DD impacting efficacy, and scalability of fungal sources over seasonal shellfish. Optimized derivatives address these for expanded clinical translation.
