Microwave-Assisted Synthesis of Nanohydroxyapatite Using a Biotemplate

Abstract

Geloina coaxans shells, which are a waste material with a high calcium source, serve as an effective raw material for synthesizing hydroxyapatite biomaterials. In this study, hydroxyapatite (HA) was synthesized from Geloina coaxans shells and ammonium hydrogen phosphate (NH₄)₂HPO₄. The eggshell membrane (ESM) was used as a biotemplate. The synthesis process of HA-biotemplate was assisted by microwave irradiation. Analysis of X-Ray Fluorescence (XRF) shows the main chemical composition in the Geloina coaxans shells is CaO of 98.15%. Analysis of X-ray diffraction (XRD) of Geloina coaxans shells showed the presence of CaCO_3, and the type was aragonite minerals in accordance with JCPDS 01-075-9987, with the highest aragonite peak at 2θ = 26.18°. Nanohydroxyapatite (HA) was synthesized at a Ca/P ratio of 1.67, with variations in the mass of the eggshell membrane (ESM). Based on the results of the Fourier Transform Infra-Red (FTIR) analysis, there is a specific absorption band in the O-H, CO₃^2- and PO₄^3- groups. The absorption band of the functional group indicates the specific functional group of the hydroxyapatite synthesized. Microstructural analysis of the HA-ESM samples (prepared with 50, 100, and 150 mg of ESM) revealed spherical granules, randomly intertwined cotton-like fibers, and cotton-like fibers with stacked short rod morphology, respectively. Changing the ESM biotemplate mass effectively dictates and transforms the resulting nanohydroxyapatite morphology. ESM, with its fibrous proteins capable of molecular recognition, serves as an attractive biotemplate for developing hierarchical architectures. The variation in mass employed can stimulate the development of the HA framework, and microwave-assisted synthesis utilizing in situ heating will also accelerate the nucleation and crystal growth of hydroxyapatite.