Desenvolvimento de biocerâmica porosa a partir da hidroxiapatita extraída de escamas de pirarucu (Arapaima gigas)

Abstract

The hydroxyapatite (Ca10[PO4]6(OH)2, HAp) is a calcium phosphate bioceramics and the main constituent of human bones and teeth. Several studies in the last decade have evaluated the extraction and characterization of HAp obtained from scales of different types of fish, aiming at its application in tissue engineering. However, bioprospecting studies of new sources of HAp in fish scales of native Amazonian biodiversity are still scarce. In the present work, the objective was to produce porous bioceramics from HAp extracted from pirarucu (Araipama gigas) scales, where there are records of HAp in the highly mineralized outer layer and nanocrystals in the collagen fibers. The scale was characterized using derivative thermogravimetry (TG-DTG) and Fourier transform infrared spectroscopy (FT-IR). The extraction of hydroxyapatite (HAp) from the fish scales was performed by calcination between 600°C and 1000°C, the HAp powders were analyzed by X-ray diffraction (XDR), Fourier transform infrared spectroscopy (FT-IR), spectroscopy of energy dispersive X-ray (EDS), scanning electron microscopy (SEM) and yield. The powder calcined at 1000°C was used for the compaction of the pellets where HAp was mixed with different proportions of ammonium bicarbonate (BCA) acting pore generator and sintered at 1200°C. The sintered pellets (porous or scaffold bioceramics) were characterized (XDR), (FT-IR), (EDS), (SEM), density, porosity and bioactivity. Analysis of the scale by TG-DTG showed a mass loss of more than 50%, which led to yields of 46 to 48% extraction of HAp powder. The characterization results converged to the assertion of HAp. In XRD the mean crystallite size of the HAp used to produce the porous bioceramics was 74 nm, and the size of the crystallites of the bioceramics varied between 114 and 131 nm. The EDS demonstrated the presence of the elements that compose the powders, with the Ca/P ratio between 1.58 and 1.73, and the presence of magnesium, sodium and potassium as trace elements. From the MEV observations, the obtained HAp consists of grains with sizes between 1-5 and more crystalline with increasing temperature, and the porous bioceramics produced showed interconnected macropores of sizes between 50 μm and 400 μm in the samples with 40 and 60% m/m BCA. All HAp bioceramics tested showed significant porosities in the range of 29-72% for 0-60% BCA mass, and the ideal was above 55% for the development of bone scaffolds to promote bone regeneration. The Bioactivity test showed formation and dissolution of apatites on the surfaces of the samples, seen by miscroscopy and the crystallinity of the samples that remained high. These results suggest that porous bioceramics developed may have potential for use in bone tissue engineering.

Keywords: Fish scales, Hydroxyapatite, Biomaterial, Scaffold, Arapaima gigas.