Materials Chemistry and Physics 99 (2006) 284–288
DC conductivity and dielectric permittivity of collagen–chitosan films
C.G.A. Lima
a
, R.S. de Oliveira
b
, S.D. Figueir
´
o
c
,
C.F. Wehmann
d
, J.C. G
´
oes
d
, A.S.B. Sombra
d,∗
a
Departamento de Engenharia Mecˆanica, Universidade Federal do Cear´a, Caixa Postal 6030, CEP 60455-760, Fortaleza, Cear´a, Brazil
b
Departamento de F´ısica, Universidade Estadual do Cear´a, Caixa Postal 6030, CEP 60455-760, Fortaleza, Cear´a, Brazil
c
Departamento de Bioqu´ımica e Biologia Molecular, Universidade Federal do Cear´a, Caixa Postal 6030, CEP 60455-760, Fortaleza, Cear´a, Brazil
d
Laborat´orio de Telecomunica¸c˜oes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de F´ısica, Universidade Federal do Cear´a,
Caixa Postal 6030, CEP 60455-760, Fortaleza, Cear´a, Brazil
Received 23 February 2005; received in revised form 14 September 2005; accepted 24 October 2005
Abstract
In this paper we studied the physicochemical and dielectric properties of collagen–chitosan films, considering the development of new biomaterials
which have potential applications in coating of cardiovascular prostheses, support for cellular growth and in systems for controlled drug delivery.
The dielectric permittivity ε
11
were obtained for the collagen and collagen–chitosan films. Our results also show that the presence of chitosan
contributes to an increase of the thermal stability of the collagen films, which is associated with the increase of the denaturation temperature of
the collagen–chitosan samples compared with the collagen sample. We believe that the increase of the organization of the microscopic structure of
the sample, results in an increase of the thermal stability. For the samples under study, the highest conductivity was obtained for the chitosan film
compared to the pure collagen film. Around room temperature it is around 10 times bigger than pure collagen.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Collagen; Chitosan; Dielectric properties; Thermal decomposition
1. Introduction
Collagen, as well as chitosan, has great potential, in the
field of biomaterials. The study of the interactions which can
occur between these two biopolymers bears a great importance.
Mainly, to consider the processing of new materials from these
two macromolecules. Collagen is the major structural compo-
nent of connective tissues. It is an important biomaterial finding
several applications as prosthesis, artificial tissue, drug carrier
and cosmetics [1]. Collagen has a unique structure, size and
amino acid sequence [2]. The collagen molecule consists of
three polypeptide chains twined around one another as in a three-
stranded rope. Each chain has an individual twist in the opposite
directions. The principal feature that affects a helix formation is
a high content of glycine and amino acid residues. The strands
are held together primarily by hydrogen bonds between adjacent
–CO and –NH groups, but also by covalent bonds. The basic col-
∗
Corresponding author. Tel.: +55 8540089909; fax: +55 8540089450.
E-mail address: sombra@fisica.ufc.br (A.S.B. Sombra).
URL: www.locem.ufc.br.
lagen molecule is rod-shaped with a length and a width of about
3000 and 15
˚
A, respectively, and has an approximate molecular
weight of 300 kDa. Monomeric collagen molecules form stable
solutions in acids, pH 3.5 and low ionic strength at tempera-
tures in the range from freezing to denaturation. In this work
collagen was prepared from bovine intestinal submucosa, with
deamidation by alkaline hydrolysis of carboxyamide side chains
of asparagine (Asn) and glutamine (Gln) residues present in col-
lagen chains, in order to develop polyanionic collagen materials
[3].
On the other hand, chitosan is a cationic polysaccharide,
which contains -1-4-linked 2-amino-2-deoxy-d-glucopyrano-
se repeat units and is readily obtained by alkaline N-deace-
tylation of chitin. Chitin is the second-most abundant biopoly-
mer in nature, widely distributed in the shell of crustacean, the
cuticles of insects and the cell walls of the fungi. Chitosan
has many useful biological properties such as biocompatibil-
ity, biodegradability and bioactivity [4,5]. This polysaccharide,
having structural characteristics similar to glycosaminoglycans,
seems to mimic their functional behavior. The inductive and
stimulatory activity of chitosan on connective tissue-rebuilding
is clearly demonstrated, and it is suggested that chitosan could
0254-0584/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.matchemphys.2005.10.027