Low Temperature Development of Nano-Hydroxyapatite from Austromegabalanus psittacus, Star fish and Sea urchin

Abstract

The study focuses the preparation and characterization (physico-chemical and mechanical) of hydroxyapatite [Ca<inf>10</inf>(PO<inf>4</inf>)<inf>6</inf>(OH)<inf>2</inf>] (HAp) from naturally occurring dead marine species widely available in Arabian sea shore; namely Austromegabalanus psittacus, star fish (Asteroidea) and sea urchin (Echinoidea). All three marine species were found to be source of calcium carbonate in the form of aragonite (calcite) that crystallize in an organic matrix. The calcined aragonite was converted to nano-sized hydroxyapatite powder by chemical reaction with Ortho-phosphoric acid while maintaining stoichiometry, Ca/P = 1.67 at 80 °C. It was found from XRD that the powders were composed of pure HAp with average crystallite size of 10 nm. SEM, on the other hand, revealed nano-rod like elongated structures having a length in the range of 100 to 700 nm with an aspect ratio of 3.5. Further, the HAp powders were used to prepare cylindrical pellet samples by uni-axial pressing, sintered at 1100 °C temperature, made flat-parallel, polished and used finally for assessment of elastic modulus by compression test method. Primary results showed typical elastic modulus of pellets from Austromegabalanus psittacus is 3 GPa, star fish 2.1 GPa and sea urchin 2.3 GPa (L/D = 1.3 and strain rate = 0.01 mm/s). Thus, the powder synthesized from marine source could be a potential alternative for development of structural bio-ceramics and also can be used as scaffolds for bone or dental implants, because of its easy and economical fabrication. © 2017 Elsevier Ltd. All rights reserved.