Collagen-hydroxyapatite films: piezoelectric properties

In this paper we report a study of the physicochemical, dielectric and piez oelectric properties of anionic collagen and collagen-hydroxyapatite (HA) c omposites, considering the development of new biomaterials which have poten tial applications in support for cellular growth and in systems for bone re generation. The piezoelectric strain tensor element d(14), the elastic cons tant s(55) and the dielectric permittivity 8(11), were measured for the ani onic collagen and collagen-HA films. The thermal analysis shows that the de naturation endotherm is at 59.47 degreesC for the collagen sample. The coll agen-HA composite film shows two transitions, at 48.9 and 80.65 degreesC. T he X-ray diffraction pattern of the collagen film shows a broad band charac teristic of an amorphous material. The main peaks associated to the crystal line HA is present in the sample of collagen-HA. In the collagen-HA composi te, one can also notice the presence of other peaks with low intensities wh ich is an indication of the formation of other crystalline phases of apatit e. The scanning electron photomicrograph of anionic collagen membranes show s very thin bundles of collagen. The scanning electron photomicrography of collagen-HA film also show deposits of hydroxyapatite on the collagen fiber s forming larger bundles and suggesting that a collagenous structure of rec onstituted collagen fibers could act as nucleators for the formation of apa tite crystal similar to those of bone. The piezoelectric strain tensor elem ent 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 literat ure 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, diel ectric permittivity and lowest frequency constant f.L. (C) 2001 Elsevier Sc ience B.V. All rights reserved.