A Novel Fast-Setting Strontium-Containing Hydroxyapatite Bone Cement With a Simple Binary Powder System.

Current research in bone tissue engineering has focused on developing biocompatible materials that can support bone regeneration while offering mechanical stability. Traditional calcium phosphate cements (CPCs) are widely used due to their osteoconductive properties and biodegradability. However, their mechanical performance and setting characteristics can be limited. Strontium (Sr) ions have been shown to enhance bone formation and improve the mechanical properties of CPCs. Despite this, the synthesis of Sr-containing CPCs often involves complex processes and high temperatures. This gap motivated researchers to explore a simplified method for producing Sr-substituted CPCs with improved physicochemical properties and favorable biological performance.

The aim of this research was to develop a novel Sr-containing CPC using a simplified synthesis method that reduces energy consumption and eliminates the need for complex multi-step processes. The study specifically investigated the physicochemical properties and hydration behavior of a new Sr-CPC system based on a binary powder of α-Ca₃-Sr(PO₄)₂ and Ca₄(PO₄)₂O. The researchers sought to determine how varying Sr content affects the setting time, compressive strength, and hydration mechanism of the cement. Additionally, they evaluated the cytocompatibility of the material to assess its potential for clinical use in bone repair applications.

The researchers synthesized a Sr-containing α-Ca₃-Sr(PO₄)₂ salt using a one-step method at a lower temperature than conventional approaches. This salt was combined with Ca₄(PO₄)₂O to form a binary cement powder system. The hydration process was monitored over time using analytical techniques to track the formation of intermediate and final products. Compressive strength tests were conducted at different hydration times to evaluate mechanical performance. Cytocompatibility was assessed using cell culture experiments to measure viability and response to Sr ion release. The study combined material synthesis, structural analysis, and biological testing to evaluate the new cement system.

The study found that the Sr-containing cement system formed a single-phase Sr-hydroxyapatite after 72 hours of setting. As Sr content increased, compressive strength slightly decreased, and setting time extended. The hydration process occurred in three distinct stages: initial formation of CaHPO₄·2H₂O (30 min–1 h), followed by complete hydration of Ca₄(PO₄)₂O and CaHPO₄·2H₂O (2–6 h), and final self-setting of α-Ca₃-Sr(PO₄)₂ (6 h onward). Compressive strength increased with hydration time, correlating with the transformation rate of Sr-hydroxyapatite. Cytocompatibility tests showed favorable results, with Sr ions having minimal impact at low concentrations. These findings suggest the new cement system has potential for orthopedic applications.

The authors concluded that the α-Ca₃-Sr(PO₄)₂ salt is a valuable Sr-containing source for developing novel biomaterials. The new binary cement system demonstrated attractive properties, including a single-phase hydroxyapatite setting product and favorable mechanical and biological performance. The study supports the clinical potential of this Sr-CPC system in orthopedic applications. The simplified synthesis method and binary powder system offer practical advantages for material development. The results align with prior research on Sr's beneficial effects on bone formation. The findings do not suggest that Sr is essential for all CPC systems but highlight its potential to enhance specific formulations. The study does not propose new drug targets or future research directions beyond material development.