The natural associations of chitins with other biopolymers

often recur in the scientific literature:

for example, at its reducing end, hyaluronan has chitooligomers

that act as templates for hyaluronan synthesis.

Likewise, composite materials of chitin with inorganic compounds

are frequently dealt with in recent publications

Chitin nanostructures in living organisms

Riccardo A.A. Muzzarelli

A chapter of the book

Chitin formation and diagenesis

Gupta N.S., Ed.

Springer, New York. 2011.

ISBN 978-90-481-9684-5

Scope of the chapter is to describe some of the most impressive chitin-based nanostructures of living organisms, to report on their performances at the biochemical and biomechanical levels, and to mention the technological importance of some chitin-based items that mimic natural nanostructures.

In living organisms, chitin synthase present in chitosomes promotes the polymerization of N-acetylglucosamine, then the native chitin is assembled into nanocrystals. The latter cluster into long chitin-protein fibers that form a planar network whose spacings are filled up with pigments, nano-sized inorganic compounds and other substances. In certain cases quinones contribute to the mechanical strength by tanning.

Elaborated but robust structures are present in arthropods, chitons, yeasts, fungi, diatoms, corals and sponges. The occurrence of a chitin-producing system is an ancestral condition observable in a number of phyla. Chitin supported many organisms during the Cambrian life explosion.

Current research on the chitinous nanostructures is today important in order to understand the roles of chitin in vivo, as well as to prepare materials for medical and veterinary applications, in particular composites for filling bone defects, hemostatic bandages for emergency management of bleeding, and non-wovens for the ordered regeneration of wounded tissues.

Figure. Hierarchical microstructure of the cuticle of the lobster Homarus americanus. Reprinted from Acta Materialia 53. Raabe D, Romano P, Sachs C. The crustacean exoskeleton as an example of a structurally and mechanically graded biological nanocomposite material. Pages 4281-4292. Copyright (2005), with permission from Elsevier.