Abstract
In this paper we did 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
epsilon(11) were measured for the anionic collagen and collagen-HA
films. For the collagen-HA composite film (Col-HACOM) the main peaks
associated to the crystalline HA is present. For the nanocrystalline
composite, nanometric HA powder (103 nm particle size) (HAN), obtained
by mechanical milling were used. For the composite film (Col-HAN) the HA
and CaH(PO4)(2)H2O phases were detected. One can see that the HA powder
(HAN) present the main peaks associated to crystalline HA. The IR
spectroscopy measurements on HA-COM and HAN powders, Col-HACOM and
Col-HAN composite films and collagen film (Col) presents the main
resonances associated to the modes of (PO4)(3)-, (CO3)(2)-. The IR
spectra of Collagen Film (Col) shows the bands associated to amide I (C=O), amide II (N-H) and amide III (C-N) vibrational modes. The
scanning electron photomicrography of the Col-HACOM and Col-HAN films,
respectively, shows deposits of HA on the surface of collagen. It also
shows that HACOM crystals has a dense feature, whereas the HAN crystals
has soft porous surface. Energy-dispersive spectroscopy (EDS) analysis
showed that the main elements of the hybrid sponge were carbon, oxygen,
calcium, and phosphorus. The EDS of HACOM crystal, present in the Col-HACOM composite showed a molar ratio Ca/P = 1.71, whereas the Col-HAN composite the molar ratio of calcium and phosphorus (Ca/P =
2.14) and the amount of carbon were greater. The piezoelectric strain
tensor element d(14) obtained for the anionic collagen was around 0.102
pC/N. The collagen composite with nanocrystalline HA crystals (Col-HAN) present a better result (d(14) = 0.040 pC/N) compared to the composite with the commercial ceramic (d(14) = 0.012 pC/N). This is an indication
that the nanometric particles of HA present little disturbance on the
organization of the collagen fibers in the composite. In this situation
the nanometric HA are the best candidates in future applications of
these composites. (C) 2002 Kluwer Academic Publishers.
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