**Biopolymer Modifications for Biomedical Applications**

M.S. Mohy Eldin1,\*, E.A. Soliman1, A.I. Hashem2 and T.M. Tamer1

*1Polymer Materials Research Department, Advanced Technologies and New Materials Research Institute (ATNMRI), Mubarak City for Scientific Research and Technology Applications (MUCSAT), New Borg El-Arab City, Alexandria 2Organic Chemistry Department, Faculty of Science, Ain-Shams University, Cairo Egypt* 

## **1. Introduction**

354 Infrared Spectroscopy – Life and Biomedical Sciences

Toichi M., Findling RL., Kubota Y., Calabrese JR., Wiznitzer M., McNamara NK., Yamamoto

Mechanical Systems, Vol. 2 (1), pp.736-744

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> Chitosan is typically obtained by deacetylation of chitin under alkaline conditions, which is one of the most abundant organic materials, being second only to cellulose in the amount produced annually by biosynthesis. Chitosan is a linear polysaccharide, composed of glucosamine and *N*acetyl glucosamine units linked by (1–4) glycoside bonds. The content of glucosamine is called the degree of deacetylation (DD). In fact, in a general way, it is considered that when the DD of chitin is higher than about 50%(depending on the origin of the polymer and on the distribution of acetyl groups along the chains), it becomes soluble in an aqueous acidic medium, and in these conditions, it is named chitosan. The DD also affects the biodegradability of this polymer, and for DD above 69% a significant decrease of *in vivo* degradation has been found (1). Chitosan displays interesting properties such as biocompatibility, biodegradability (3, 4) and its degradation products are non-toxic, non-immunogenic and non-carcinogenic (5, 6). Therefore, chitosan has prospective applications in many fields such as biomedicine, waste water treatment, functional membranes and flocculation. However, chitosan is only soluble in few dilute acid solutions, which limits its applications.

> Recently, there has been a growing interest in the chemical modification of chitosan in order to improve its solubility and widen its applications (7–9). Derivatization by introducing small functional groups to the chitosan structure, such as alkyl or carboxymethyl groups (10, 11) can drastically increase the solubility of chitosan at neutral and alkaline pH values without affecting its cationic character.

> Substitution with moieties bearing carboxylic groups can yield polymers with polyampholytic properties (12). The antimicrobial activity of chitosan increases with decreasing pH (13-17). This is due to the fact that the amino groups of chitosan become

<sup>\*</sup> Corresponding Author

Biopolymer Modifications for Biomedical Applications 357

PBQ :chitin ratio N % Chitosan control 7.42 0.0935 7.50 0.187 7.56 0.374 8.73 0.545 9.60 0.747 9.62

Table 1. Effect of PBQ concentration on the nitrogen content of modified chitosan

In the characterization of modified chitosan membranes, different characters were monitored to show the effect of modification process on their properties. The occurrence of amination process was verified through examination of the chemical structure changes

The FTIR spectrum of the modified chitosan and intermediates to verify structure changes was obtained using FTIR-8400S SHIMDZU. Japan. As shown in figure 2, the major difference are the wide peaks at 3431 cm-1, (I) corresponding to the stretching vibration of – NH2 and OH groups became more sharp at modified chitosan as result of alternation of –OH groups with –NH2 groups. Absorption band intensity at 1560, 1649 cm-1 (II) corresponding to carbonyl bands have been increased in (AC ), curve (b), via introduce further carbonyl groups of PBQ as illustrated in schema1, then return to normal at aminated chitin, curve (c). Finally, peaks will reduced after deacetylation as a result of removal the acetyl groups in modified chitosan. This observation confirmed the occurrence of the modification process

Fig. 2. FTIR spectra of chitin (a), activated chitin (AC) (b), aminated chitin (c) and modified

**2.1 Characterization of modified chitosan membranes** 

using FT-IR, TGA analysis and solubility test.

with different steps indicated in figure 1.

chitosan (d).

ionized at pH below 6 and carry a positive charge. Unmodified chitosan is not antimicrobially active at pH 7, since it does not dissolve and also since it does not contain any positive charge on the amino groups (18, 19). The antimicrobial activity of chitosan also increases with increasing degree of deacetylation, due to the increasing number of ionisable amino groups (19). Several approaches were done to increase the antimicrobial activity of chitosan by introduce amino groups, on the primary amino groups of the back bone of chitosan polymer chains but it was failed (20). The obtained results were explained based on the remote position of the new introduced amino groups.

In this work, we aim to increase both the solubility and antimicrobial activity of chitosan via increase the amino groups on the polymer back bone by attaching amino groups directly on the hydroxyl groups of polysaccharide to wide its applications.

A new technique has been used to avoid the consumption of the original amino groups of the chitosan as sites of grafting, so chitin was first grafted with amino groups in separate step then it was de-acetylated to have the aminated chitosan. Aminated chitosan was tested as antimicrobial agent and aminated chitosan membranes were prepared, characterized and evaluated for wound dressing applications.
