A preface to the chitosan—biopolymer, its origin, and properties

Biopolymers have played different and important roles in human history. First, these macromolecules were used as raw materials to cover primary necessities. Nowadays, the uses and applications of biopolymers (proteins, nucleic acids, and polysaccharides) are broad, encompassing various fields of science, industry, and technology. Among polysaccharides, chitosan is of great interest in the fields of material science, chemistry, engineering, agriculture, medicine, and pharmacology, to the development of novel functional materials and devices.