چكيده فارسي :
Recent studies of the chemical modification of chitin and chitosan are discussed from the
viewpoint of biomedical applications. Special emphasis is placed on the role of individual
functional groups in applications of modified chitosan. Among chitosan derivatives,
quaternary ammonium chitosan, carboxyalkylchitosans and N-acyl chitosan and O-acyl
chitosan, are some types of modified chitosans, which have been studied intensively in order
to improve solubility, biological properties and find new applications [1,2]. Chitosan and its
derivatives are useful as carriers in drug delivery systems, as antibacterial agents, and in other
medical applications. In this work, 2,4-Dihydroxybenzoic acid covalently conjugated to
chitosan via a 1-ethyl-3-(3-dimethylaminopropyyl)- carbodiimide-mediated (EDC-mediated)
and N-hydroxylsuccinimide (NHS) reaction to generate chitosan derivatives. Modified
chitosans were prepared under homogenous conditions in 1% acetic acid solution. The
reaction occurs between the amino groups of chitosan and carboxyl groups of
dihydroxybenzoic acid in the presence of EDC and NHS. EDC and NHS have been used as
the activating agents for the amide bond formation. In the FT-IR analysis of chitosan, specific
peaks of chitosan are observed at 1659 cm-1, 1630 cm-1 and 1564 cm-1, which are attributed to
the C=O stretching vibration of amid I, N-H bending vibration of amine and N-H bending
vibration of amide II, respectively[3]. Compared to the FT-IR spectrum of chitosan, the
spectrum of CS-DH showed new peaks at 1654 cm-1 and at 1546 cm-1, attributed to the
carbonyl stretching vibration of amide I and N-H bending vibration of amide II, respectively.
In the 1H-NMR spectra of CS-DH, in addition of the protons of repeating unit of chitosan,
protons of aromatic ring (H-arom) appear at 6.7 (H-8), 6.9 (H-7) and 7.3 (H-9), respectively.
