Luminescent calcium phosphate bioceramics doped with europium derived from fish industry byproducts

The recovery of valuable compounds from byproducts is at present a priority topic for social, environmental, and economic reasons. In this work we report for the first time the preparation of luminescent calcium phosphate (CaP) bioceramics from waste codfish bones. Codfish bones were treated in aqueous Eu(NO₃)₃ solutions of different concentrations, followed by thermal treatment at either 700°C or 1100°C. The resulting materials consisted of hydroxyapatite (HAp), β-tricalcium phosphate (β-TCP) and a small amount of Eu₂O₃. Chemical and structural characterization showed that the Eu ions were successfully introduced into the bones and, hence, in the thermally treated CaP phases obtained from them, although mainly in the β-TCP lattice. Photoluminescence investigation revealed that all the materials are luminescent, with samples treated at 1100°C having more intense luminescence than those prepared at 700°C. In vitro evaluation of cell-materials interaction indicated that all the samples displayed good cytocompatibility toward osteoblast cells. This work demonstrates that a simple and effective process, employing Eu as a dopant, can convert fish industry byproducts into highly valuable luminescent CaP bioceramics, having potential applications in biology and medicine for bio-imaging.