Conversion of calcite from cockle shells to bioactive nanorod hydroxyapatite for biomedical applications

摘要

Bioactive ceramics such as hydroxyapatite (HA) can mimic the organic structure of human bone. HA was successfully synthesized from animal bones, corals, and eggshells which have been studied for bone repairing treatment and as implant coatings. This study aims to synthesize nanorod HA from cockle shells via two routes: calcination and the hydrothermal method. The raw cockle shells were converted to calcite by calcination method at 450 degrees C (CS450) and 800 degrees C (CS800) for 2 hrs. The calcite calcium carbonate samples were reacted with diammonium hydrogen phosphate and hydrothermally treated at 110 degrees C. The pH of the solution was kept at 10.5 throughout the synthesis step by adding drops of ammonia. Product obtained was labelled as HA450 and HA800 containing HA powder. Presence of calcite phase in the raw cockle shells was characterized by utilizing Thermogravimetric analysis (TGA), X-ray Diffraction (XRD) and Fourier transforms infrared spectrophotometer (FTIR) analyses and morphologically analyzed by Field emission scanning electron microscopy (FESEM). The best result was obtained from the HA800 sample where nanoparticle with rod-like shape was observed (aspect ratio = 7) while needle-like particle was seen in HA450 sample (aspect ratio = 20). High purity HA was developed in HA800 sample while HA450 showed small presence of calcite phase. In vitro bioactivity test of HA powder samples incubated simulated body fluid (SBF) for 1, 3, 8, 15 and 21 days showed high bioactivity in both samples by forming apatite agglomerate on the surfaces. Higher microhardness strength was observed in HA800 compared to HA450, CS450 and CS800 sintered pellet samples.