Event Abstract Back to Event Zn release behavior of amorphous calcium phosphate and alginate gel composite Tomohiro Uchino1, Tomomi Nakanome1 and Tomoya Mori1 1 Nihon University, College of Engineering, Japan Introduction: Some cements for bone substitute has an advantage on injectable and regardless of bone defect appearance. Amorphous calcium phosphate (ACP) is considered a precursor to bone hydroxyapatite (HAp; Ca10(PO4)6(OH)2)[1]. Zn is a trace element as bone formation[2]. Alginate gel is a non-toxic material that can serve as a medium for controlled active ingredients release[3][4]. In this study, we prepared injectable Zn-containing gel composites consisting of alginate and ACP. Then, we try to investigate the Zn release behavior from the composites in an environment of mimicking bone metabolism. The obtained samples were injected and immersed in an acetic acid buffer solution (AcBu) mimicking the peripheral environment of active osteoclasts or in a simulated body fluid (SBF: Kokubo’s solution) mimics the environment of active osteoblasts. After immersing the samples in AcBu or SBF solutions, the Zn release behavior and characterization of the samples were investigated. Materials and Methods: CaCl2∙H2O and NaH2PO4 solutions were mixed at a 1:1 molar ratio of Ca and P. The mixed solution was added to a stirred NaOH solution at less than 4ºC and a pH10. The precipitates were filtered, washed with acetone, and freeze dried. ZnSO4 solution and sodium alginate solution (Alg) were mixed. This solution was mixed with obtained ACP powder with an emulsion needle (AlgZn-Ca). For another preparation, the ACP powder and Alg were mixed first, and then, mixed with Zn solution (CaAlg-Zn). These AlgZn-Ca or CaAlg-Zn gel composite sample was injected into 30 cm3 of AcBu or SBF at 37ºC for 1, 3, and 7 days. Immersing for 1 and 3 days, 10 cm3 of immersed solutions were exchanged for new solution. After immersing 7 days, gel composite samples were dried at room temperature. Zn, Ca and P concentrations in AcBu and SBF before and after immersing the samples were measured. For alginate gel characterization, Zn or Ca containing alginate gel was synthesized by dropped Zn or Ca solution into alginate solution. Results and Discussion: The Zn release behavior of these gel composites is shown in Fig. 1. The Zn release rate of ZnAlg-Ca was slower than CaAlg-Zn in AcBu. Similarly, Ca and P were released from the composites in AcBu. After immersing ZnAlg-Ca in AcBu for 7days, 80% of Zn was released. In contrast, after immersed these samples in SBF for 7 days, less than 1% of Zn was released from these samples. The Zn release rate would be controlled by alginate cross-linked Zn2+. Alginate forms a gel with divalent cations (Ca2+, and Zn2+) as cross-linking points. From DTA measurement, exothermal peak was detected at 530ºC of Zn2+ containing gel, in contrast, the peak was detected at 700ºC of Ca2+ containing gel (Fig. 2). The ZnAlg-Ca sample formed alginate gel by Zn2+ would make Zn slower release. Conclusion: The alginate gel was effective for controlling Zn release and making injectable samples. The gel composite samples were expected to be a new controlled release injectable bone substitutes. JSPS KAKENHI Grant Number 26861688.