Aqueous ammonia

Mesoporous bioactive glass nanoparticles (MBN) were synthesized with a modified method from Lee et al. [36 (link)] and El-Fiqi et al. [37 (link)]. In 150 mL distilled water, 2-ethoxyethanol (Sigma-Aldrich, St. Louis, MO, USA), 2 mL aqueous ammonia (Samchun, Pyeongtaek, South Korea), 1.4 g calcium nitrate tetrahydrate (Ca(NO₃)₂·4H₂O) (Sigma-Aldrich), and 20 mL ethanol (Samchun, Pyeongtaek, South Korea) were combined; then, 1 g hexadecyltrimethylammonium bromide (CTAB) (Sigma-Aldrich) was added, and the mixture was stirred for 30 min at room temperature. After adding 5 mL of tetraethyl orthosilicate (TEOS) (Sigma-Aldrich), 4 h of vigorous stirring was performed. The molar ratio (mol %) of the resulting CaO:SiO₂ was calculated to be 15:85. A white precipitate was obtained, which was washed with ethanol and dried for 24 h at 60 °C. To remove CTAB, calcination was performed for 5 h at a heating rate of 1 °C·min⁻¹ at 600 °C.

MBN were synthesized by modified sol-gel method [2 (link)]. Briefly, in 150 mL of distilled water, 10 mL 2-ethoxyethanol (Sigma-Aldrich, St. Louis, MO, USA), 2 mL aqueous ammonia (Samchun, Seoul, Korea), 1.4 g calcium nitrate tetrahydrate (Ca (NO₃) ₂.4H₂O) (Sigma-Aldrich, St. Louis, MO, USA), 20 mL ethanol (Samchun, Seoul, Korea), and then 1 g hexadecyltrimethylammonium bromide (CTAB, Sigma-Aldrich, St. Louis, MO, USA) were added. After 30 min stirring, 5 mL and 0.25 mL of tetradecyl acetate (TEOS, Sigma-Aldrich, St. Louis, MO, USA), Triethyl phosphate (TEP, Sigma-Aldrich, St. Louis, MO, USA) were added sequentially and stirring for 4 h vigorously. The mole (Mol%) ratio of CaO: SiO₂: P₂O₅ was 36:60:4. The white precipitates were obtained, dried at 60 °C for 24 h, and calcinated at 600 °C for 6 h with a heating rate of 1 °C min⁻¹ and then furnace cooled naturally.

MBN was synthesized using a modified sol-gel process. Briefly, 3.12 g calcium nitrate tetrahydrate (Ca(NO₃)₂·4H₂O) (Sigma-Aldrich, St. Louis, MO, USA), 2 mL aqueous ammonia (Samchun, Seoul, Korea), 10 mL 2-ethoxyethanol (Sigma-Aldrich, St. Louis, MO, USA), 20 mL ethanol (Samchun, Seoul, Korea), and 1 g hexadecyltrimethylammonium bromide (CTAB) (Sigma-Aldrich, St. Louis, MO, USA) were mixed in 150 mL distilled water. The mixture was stirred at room temperature for 30 min. Then, 5 mL tetraethyl orthosilicate (TEOS; Sigma-Aldrich, St. Louis, MO, USA) was added and stirred at room temperature for 30 min. Subsequently, 0.25 mL triethyl phosphate (TEP; Sigma-Aldrich, St. Louis, MO, USA) was added and the mixture was vigorously stirred for 4 h at room temperature. A white precipitate was formed and dried in a vacuum oven at 60 °C for 24 h. The dried gel powder was calcined at 600 °C for 5 h. The molar ratio of SiO₂:CaO:P₂O₄ was calculated to be 60:36:4.