The effect of synthesis parameters on the geometry and dimensions of mesoporous hydroxyapatite nanoparticles in the presence of 1-dodecanethiol as a pore expander.

Mesoporous hydroxyapatite with different pore diameters and pore volumes were synthesized by the self-assembly method using Cetyltrimethylammonium bromide (CTAB) as the cationic surfactant and 1-dodecanethiol as the pore expander at different micellization pHs, solvent types and surfactant concentrations. Results of field emission scanning electron microscopy (FESEM) showed a decrease in length/diameter ratio of rod-like particles by an increase in micellization pH and also a sphere to rod transition in morphology by an increase in CTAB concentration. Brunauer-Emmett-Teller (BET) surface area and Low angle X-ray diffraction analysis revealed that the optimized mesoporous hydroxyapatite with controlled pore structure can be obtained under basic micellization pH (about 12, pH of complete ionization of 1-dodecanethiol) by using water as the solvent and a high content of cationic surfactant. The results also show that micellization pH has a strong effect on pore structure and changing the pH can shift the mesostructure to a macroporous structure with morphological changes.

In vitro antibacterial evaluation of sol-gel-derived Zn-, Ag-, and (Zn + Ag)-doped hydroxyapatite coatings against methicillin-resistant Staphylococcus aureus.

Hydroxyapatite (HAp) coatings were applied using sol-gel method. Phosphor pentoxide and calcium nitrate were used as phosphorous and calcium precursors, respectively. Zinc nitrate and silver nitrate were used as substitute of calcium in HAp structure. As a base concentration, 1.5 wt %Ag and 2.5 wt %Zn were used. The weight percent of Ag was increased at 0.3 wt% and Zn content was scaled down at 0.5 wt%. Phase analysis and chemical bonds of synthesized materials were studied by XRD and FTIR. Antibacterial activity of Ag- and Zn-doped samples against methicilin-resistant Staphylococcus aureus (MRSA) were assessed by the plate-counting method. The XRD and FTIR results proved formation of HAp compound. Colony counting showed that silver and zinc ions prevent proliferation and growth of MRSA. Interestingly, co-presence of metal ions improves the antibacterial effectiveness of the coatings and the combined effect was greater than sum of the individual effects when each was administered alone. Overall, synergism between antibacterial activities of Zn(2+) and Ag(+) ions against MRSA can be suggested. Thus, cell toxicity decreases and biocompatibility increases without any decrement in antibacterial activity.