Controlling pore size during the synthesis of hydroxyapatite nanoparticles using CTAB by the sol–gel hydrothermal method and their biological activities

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Abstract Nanorod and nanosphere hydroxyapatite (HAP) particles were synthesized by the sol–gel hydrothermal method. The size of the synthesized HAP nanoparticles was controlled using cetyltrimethylammonium bromide (CTAB) as a templating agent with molar concentrations (HAP + 0.01 M CTAB, HAP + 0.03 M CTAB, and HAP + 0.1 M CTAB). The purity, size, shape, and elemental composition of HAP were determined using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy, which enabled us to determine the nanostructure formation. Further, Brunauer–Emmett–Teller analysis of the samples proves the size of the pores to be 7–10 nm. Thus, by altering the concentration of CTAB, HAP nanorods were induced along the c-axis. The zeta potential values of −34.7 and −28.7 mV confirmed the stability of pure HAP and HAP + 0.01 M CTAB. Further, the biological activities of the HAP nanoparticles were determined. In the anti-microbial activity test, an increase in the inhibition with an increase in the concentration of pure HAP to 0.1 M CTAB + HAP was observed against S. aureus, S. pyrogens, B. subtilis, E. aerogens, K. pneumoniae, and P. vulgaris. About 76% of antioxidant activity was obtained from the experiments. The drug-release behavior of doxorubicin-loaded pure HAP and CTAB-coated HAP also indicates that the % of drug delivery depends on the pores, which further depends on the CTAB concentration. The cytotoxic assay also revealed potential inhibitory effects against human cancer cell lines (MCF-7), with 65% cell viability recorded at a concentration of 500 μg/ml. These findings indicate that the pore size and shape of HAP play significant roles in their biological activities.