Prawn Exoskeleton Derived Calcium Phosphates and their Composites for Bone Regeneration

Abstract

In the present study, various calcium phosphates like hydroxyapatite (HA), biphasic calcium phosphates (BCP) and β-tri calcium phosphate (β-TCP) were synthesized from prawn (Fenneropenaeus Indicus) exoskeleton powder. The obtained calcium phosphates were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photo electron spectroscopy (XPS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA). The calcination temperature of 723 C was appropriate for the thermal decomposition of calcite to calcium oxide (CaO). Hydroxyapatite and biphasic calcium phosphates are derived from prawn shell biowaste through a wet chemical treatment of CaO. Hydroxyapatite dense scaffolds sintered at 1100 C showed compressive strength of 26.5 MPa. In biphasic calcium phosphates, the specimens sintered at 1100 C showed the compression strength of 56.8 MPa. X-ray diffraction (XRD) pattern revealed the phase-pure crystalline rhombohedral crystal structure of β-TCP with an average crystallite size of ~25.8 nm, prepared at 1100 C through solid state reaction approach with Ca:P ratio of 1.5. Furthermore, the SEM and EDS opened up well sintered uniaxial grains and the presence of trace elements like Fe, Mg, Si, and Na. A major objective of this work is to explore the mechanical properties of calcium phosphates and their composites with clay. In this study, a cost-effective method to prepare HA-clay composite was demonstrated via the mechanical mixing method, where kaolin and bentonite were used, because of their biocompatibility. Addition of 20 % kaolin to HA enhanced the compressive strength by 33.7 % and addition of 30 % bentonite to HA enhanced the compressive strength by 6 times when compared with bare HA.