Structural characterization and antibacterial activity of hydroxyapatite synthesized via sol-gel method using glutinous rice as a template

The present work aims to synthesize hydroxyapatite (HAp) via green template addition using glutinous rice (GR) in combination with sol-gel route under various calcination temperatures (500–900 °C). The physicochemical properties of GR-HAp were analyzed using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray analysis. The utilization of GR as template in HAp synthesis resulted in the formation of GR-HAp particles that are less crystalline. Surface morphology revealed discrete, rod-shaped GR-HAp particles were formed at low calcination temperature (500–600 °C), while larger particles were formed as temperature was increased. Results confirmed that higher calcination temperature led to the transformation of HAp into various phases including β-Ca3(PO4)2, CaO, and β-NaCa(PO4). In addition, the formation of smaller, elongated GR-HAp particles with diameter of 75–180 nm and homogenous particle size distribution was attained at 900 °C. The antibacterial activity was evaluated via disc diffusion method against four Gram-positive bacteria including B. cereus, B. subtilis, S. aureus, and S. epidermidis, and two Gram-negative bacteria including E. coli and P. aeruginosa. The GR-HAp powder calcined at 900 °C showed strong antibacterial performance against all bacterial strains with inhibition zones ranging from 11.66–16.66 mm, which indicates its suitability to be utilized as a material in biomedical applications.