Table 1.

Modification of chitosan and its derivatives and their significant properties.

Types	Functional Group	Common Derivatives	Applications	Reference
Thiolated chitosan derivatives	the thiol groups	chitosan-6-mercaptonicotinic acid; chitosan-4-thiobutylamidine;	Tissue-engineered scaffolds; Drug delivery nanocarriers; Wastewater treatment; Antibacterial activity;	[13]
Phosphorylation of chitosan derivatives	phosphate groups	N-methylene phosphonic chitosan	Induced bone formation; Increased solubility; Fuel cell;	[14]
Crosslinked chitosan derivatives	cross-linking bridges	Ethylene diamine tetraacetic acid chitosan polymer; Chitosan-glutaraldehyde cross-linked polymers;	Drug delivery systems; Biosorbents;	[15]
Carboxylic acid chitosan derivatives	Carboxymethyl group	N, O-carboxymethyl chitosan; N, N-carboxymethyl chitosan; Chitosan-methacrylate;	Tissue engineering scaffold materials; food industry; nanobiosensors	[16]
Cationic chitosan derivatives	quaternary functional groups	N-(2-hydroxy) propyl-3-trimethylammonium chitosan; chitosan-(mono, di, tri)chloroacetate; chitosan-trifluoroacetate;	Antibacterial activity; Increased water solubility; Antioxidant reagent;	[17]
Sulfated chitosan derivatives	–SO42− groups	6-O-sulfated chitosan; 2-N,6-O-sulfated chitosan;	Tissue repair and regeneration; anticoagulation; antioxidant; antiviral	[18]