Green synthesis and characterization of hydroxyapatite nanoparticles using cow dung for biomedical applications

The green synthesis of hydroxyapatite (HAp) nanoparticles using cow dung (CD) extract offered a sustainable alternative for biomedical applications. HAp, renowned for its biocompatibility and osteoconductivity, was synthesized using Ca(OH)₂ and NaH₂PO₄·2H₂O with varying concentrations of CD extract. In this study, synthesis parameters were optimized, and the resulting nanoparticles were characterized using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM).  X-ray Diffraction confirmed the crystalline phase of nHAp with characteristic peaks, while minor peak shifts in nHAp/CD samples indicated interactions between organic components of CD and the HAp lattice. Lattice parameter analysis revealed reduced unit cell volumes, signifying structural modifications induced by the green synthesis process. Fourier Transform Infrared spectra showed characteristic OH⁻ and PO₄³⁻ groups, confirming successful HAp formation. Slight variations in vibrational modes provided further evidence of organic interactions from the CD extract, in agreement with the XRD findings. Thermogravimetric Analysis demonstrated enhanced thermal stability in CD-derived HAp. The nHAp/CD 10.0 mL sample exhibited the lowest total weight loss (14.28%), compared to 35.24% for pure nHAp, highlighting the stabilizing effect of CD components. SEM analysis revealed concentration-dependent morphological evolution: pure nHAp formed dense clusters, whereas nHAp/CD 10.0 mL produced dense rod-like structures. Higher CD extract volumes resulted in needle-like morphologies (nHAp/CD 6.00 mL), while lower volumes yielded porous, cloud-like structures (nHAp/CD 2.00 mL). These findings demonstrated that CD extract influenced the crystal growth, morphology, and thermal stability of HAp nanoparticles. The study established a green synthesis route capable of tuning HAp properties, combining enhanced crystallinity, diverse morphologies, and improved thermal behavior. Cow dung-derived HAp presented a promising, eco-friendly material for advanced biomedical applications.