Hydroxyapatite from biowaste for biomedical applications: obtainment, characterization and in vitro assays

The use of biogenic residues to obtain calcium phosphate compounds, mainly hydroxyapatite (HAp), is an excellent alternative to reduce costs in obtaining biomaterials. The purpose of this study was to obtain hydroxyapatite from fish bones and hen eggshells by alkaline hydrolysis and precipitation, respectively, and compare them to HAp obtained from calcium commercial source based on physical-chemical properties and in vitro assays. The biomaterials obtained were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) method and Fourier Transform Infrared Spectroscopy (FTIR). The XRD results revealed the presence of the main characteristic peaks of single HAp phase and FTIR analysis showed various functional groups, such as PO₄^3-, CO₃^-2 and OH^-, confirming the presence of HAp. SEM observations of the synthesized HAp showed a rod-like and spherical-like morphology. The cell viability and bioactivity of the materials were evaluated by rezasurin reduction and McCoy medium assays, respectively. The biomaterials obtained had no toxic effect and the sample obtained from fish bone was more bioactive when compared to the others. Therefore, the biowastes can be used as an alternative source of calcium in the synthesis of hydroxyapatite with promising properties for application in the biomedical area.

Keywords:
Hydroxyapatite; biomaterial; biowaste; eggshell; fishbone; recycling