Abstract
In this paper we report a study of the physicochemical, dielectric and
piezoelectric properties of anionic collagen and collagen-hydroxyapatite
(HA) composites, considering the development of new biomaterials which
have potential applications in support for cellular growth and in
systems for bone regeneration. The piezoelectric strain tensor element
d(14), the elastic constant s(55) and the dielectric permittivity 8(11),
were measured for the anionic collagen and collagen-HA films. The
thermal analysis shows that the denaturation endotherm is at 59.47
degreesC for the collagen sample. The collagen-HA composite film shows
two transitions, at 48.9 and 80.65 degreesC. The X-ray diffraction
pattern of the collagen film shows a broad band characteristic of an
amorphous material. The main peaks associated to the crystalline HA is
present in the sample of collagen-HA. In the collagen-HA composite, one
can also notice the presence of other peaks with low intensities which
is an indication of the formation of other crystalline phases of
apatite. The scanning electron photomicrograph of anionic collagen
membranes shows very thin bundles of collagen. The scanning electron
photomicrography of collagen-HA film also show deposits of
hydroxyapatite on the collagen fibers forming larger bundles and
suggesting that a collagenous structure of reconstituted collagen fibers
could act as nucleators for the formation of apatite crystal similar to
those of bone. The piezoelectric strain tensor element d(14) was
measured for the anionic collagen, with a value of 0.062 pC N-1, which
is in good agreement compared with values reported in the literature
obtained with other techniques. For the collagen-HA composite membranes,
a slight decrease of the value of the piezoelectricity (0.041 pC N-1)
was observed. The anionic collagen membranes present the highest
density, dielectric permittivity and lowest frequency constant f.L. (C)
2001 Elsevier Science B.V. All rights reserved.
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