Biocompósitos de gelatina de pele e hidroxiapatita de escamas de resíduos do beneficiamento de tilápia do Nilo (Oreochromis niloticus)

Abstract

Compounds based on calcium phosphate, among them hydroxyapatite, record several technological applications, such as biocomposites. Hydroxyapatite is widely used as biomaterial because of its excellent biocompatibility. Scales of Nile tilapia (Oreochromis niloticus) are composed of an organic fraction (collagen) and another inorganic (mainly phosphates). The skins, they are great sources for extracting collagen/gelatine. The objective of this work was the extraction and characterization of hydroxyapatite of fish skin and scales, gelatine for the production of biocomposite as an alternative for the recovery of this residue. An alkaline heat treatment was used to obtain hydroxyapatite and alkali/acid for gelatin. The scale was characterized in terms of ash, moisture, lipids, proteins and minerals. The obtained materials were characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), spectroscopy of Dispersive energy (EDS), gel permeation chromatography (GPC) and isoelectric point of gelatin. The presence of hydroxyapatite in the scale was demonstrated not only by the analysis of minerals (Ca and P) and EDS with intense peaks, but also by the ash content of 28.39%, confirming the mineral phase. In the SEM, the mineral particles appear interconnected between the collagenous fibers of the scales and the typical FTIR bands at 567 and 603 cm-1, characteristic of P-O vibrations, 1045 cm-1, may be associated with P-O bonding in PO43- groups, and The bands of 3440 cm-1 and 1645 cm-1 are typical of the O-H linkages. In addition, the XRD confirms the crystalline phase of hydroxyapatite, reinforcing that the scale is a source of the material. The characterization of gelatine also shows that it has a good molecular weight according to the source of the production, just as the FTIR bands confirm the presence of typical amide I, II and III constituents. The isoelectric point found was PI = pH = 8.6. The treatments present potential for obtaining hydroxyapatite and gelatine, as well as development of biocomposite.