**5. Conclusions**

The objective of this review is to update and discuss important aspects related to chitin extraction from different sources and methods for obtaining and purifying chitosan (CS) and for chemically modifying chitosan to obtain CS derivatives with adequate properties. The particular position of the CS and its derivatives is due to the possibility of oil-based products replacement. Several chemical modification methods for CS have also been described in this review as well as for the preparation of hydrogels based on CS or CS derivatives are widely used in the last decades because of the multiple properties allowing many applications. The state of the art is the use of CS and its derivatives combined (or not) with synthetic or natural (sometimes nanostructured) moieties. Although patents and papers mentioning new structures and properties in materials derived from CS and CS derivatives appear in the literature almost every day, this review demonstrates that the window of opportunities in research and development is still opened. The influence of the molecular weight of the CS and CS derivative hydrogels mainly on biological properties can be pointed out as one of the future trends in this field. In addition, environmentally correct methods for extracting CS should be developed taking into account the fact that the water, extensively used in CS extraction/purification, will run out quickly. More comprehensive and in-depth studies will expand the understanding of the structure-properties-applications relationship of CS and CS derivative hydrogels, which will certainly further enhance the importance of this soft material class.

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provided the original work is properly cited.

\*Address all correspondence to: ecmuniz@uem.br

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Hydrogels Based on Chitosan and Chitosan Derivatives for Biomedical Applications*

*DOI: http://dx.doi.org/10.5772/intechopen.81811*

**Author details**

Kessily B. Rufato1

André R. Fajardo6

Edvani C. Muniz1,2\*

Pinhalzinho, SC, Brazil

Elisangela Corradini2

, Juliana P. Galdino2

, Fauze A. Aouada7

, Kamila S. Ody2

1 Chemistry Department, State University of Maringa, Maringá, PR, Brazil

3 Federal Technological University of Paraná, Dois Vizinhos, PR, Brazil

4 Federal Technological University of Paraná, Apucarana, PR, Brazil

6 Federal University of de Pelotas, CCQFA, Pelotas, RS, Brazil

2 Federal Technological University of Paraná, PPGCEM, Londrina, PR, Brazil

5 Food and Chemical Engineering Department, Santa Catarina State University,

7 Grupo de Compósitos e Nanocompósitos Híbridos (GCNH), Department of Physics and Chemistry, Programa de Pós-Graduação em Ciência dos Materiais, São Paulo State University (UNESP), School of Engineering, Ilha Solteira, SP, Brazil

, Alessandro F. Martins1,2,4, Alexandre T. Paulino5

, Felipe A. La Porta2

, Antonio G.B. Pereira<sup>3</sup>

, Adley F. Rubira1

,

and

,
