WEN Shaozhen ¹, NIE Quanyi ^{2, 3}, SUN Ming ¹, LI Tianmin ¹, ZHOU Litao ¹, ZHU Qingxia ^{1, 3}

(1. Tianjin Key Laboratory of Advanced Fibers and Energy Storage, School of Material Science and Engineering,

Tiangong University, Tianjin 300387, China; 2. Chaozhou Three-Circle (Group) Co., Ltd., Chaozhou 521000,

Guangdong, China; 3. School of Material Science and Engineering, Jingdezhen Ceramic University,

Jingdezhen 333403, Jiangxi, China)

Abstract: Template method is usually used to regulate self-assembly of microspheres. However, the presence of template could be harmful to health and environment. Strontium and fluoride substituted hydroxyapatite (Sr-FHA) porous microspheres were successfully fabricated by using hydrothermal method, with the assistance of only Sr-F ion and the regulation of urea. The effects of urea on microstructural, self-assembly and in-vitro F-release properties of the porous microspheres were studied by using XRD, FTIR, SEM and BET. The nucleation-growth and self-assembly of the microspheres can be well adapted by controlling the concentration of urea. The synthesized Sr-FHA microspheres, with large specific surface area of 91.8 m2·g−1, large pore volume of 0.53 cm3·g−1 and complex porous structure, were helpful for the adsorption and long-term stable release of F−. The release concentration of F− in physiological saline solution was within the range of fluoride therapy for 30 days and would not cause fluorosis. Our Sr-FHA microspheres can be used as bioactive fluoride-release carriers for the

treatment of osteoporosis and bone defects.

Key words: urea; self-assembly; slow-release of fluoride; porous microspheres; strontium fluoride co-doped hydroxyapatite