SYNTHESIS NANO BIPHASIC CALCIUM PHOSPHATE BY UNTRASOUND ASSISTED PROCESS FOR BIOMATERIAL APPLICATION Ngoc Quyen Tran 1 , Cuu Khoa Nguyen 1 Hoang Nguyen 1 , Kim Lien Pham 2 and Thị Phuong Nguyen 1 1 Institute of Applied Materials Science, Vietnam Academy of Science and Technology, 2 Lac Hong University, Dong Nai province *Email: ntphuongvc@yahoo.com.vn; tranngocquyen979@yahoo.com Tóm tắt Nano calcium phosphat vật liệu được ứng dụng trong lĩnh vực y sinh. Các hạt nano biphasic calcium phosphat (hỗn hợp của Hydroxyapatite và tricalcium phosphat) được tổng hợp bằng phương pháp kết tủa calcium chloride và tri-sodium phosphat kết hợp sóng siêu âm. pH của phản ứng được duy trì ở 7, 9 và 11 bằng cách thêm dung dịch natri hydroxide vào hệ phản ứng. Cấu trúc của BCP được xác định bằng phương pháp nhiễu xạ tia X (XRD), phổ hồng ngoại (FTIR). Hình thái của nano BCP được xác định bằng phương pháp kính hiển vi điện tử quét (SEM). Từ khóa: biphasic calcium phosphat, calcium phosphate, sóng siêu âm Abstract Nanoscale calcium phosphates is a promising material for biomedical applications. Biphasic calcium phosphate nanopowders (mixture of Hydroxyapatite and tricalcium phosphate) were prepared by precipitation method under ultrasonic irradiation using calcium chloride and tri- sodium phosphate. The pH of the reaction system was maintained at 7, 9 and 11 by adding of sodium hydroxide solution. The calcined powders were characterized by using X-ray powder diffraction(XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Key words: biphasic calcium phosphate, ultrasonic, calcium phosphate. 1. INTRODUCTION Calcium phosphates have received most attention for bone repair applications because they have the requisite characteristics to be excellent candidates for biomaterial applications [1-2]. Moreover, calcium phosphates have a high adsorption capacity for serum proteins, such as fibronectin and vitronectin. Therefore, using of calcium phosphates as bone repair materials could result in enhancing attachment of osteoblast cells. On the other hand, calcium phosphate gradually dissolved to release calcium and phosphate ions, which are beneficial to bone formation [3-5]. Among calcium phosphate ceramics, such as hydroxyapatite (HAp) and TCP (tricalcium phosphate), osteoinductivity of BCP (HAp and TCP) has been reported as more efficient than HAp alone for repair of periodontal defects, and having better osteoinduction than single phasic HAp or TCP. HAp is stable in body fluid, while TCP is rather soluble. On the other hand, the dissolution rate of HAp in human body after implantation is too low to achieve the optimal results while the dissolution rate of TCP is too fast for bone bonding. Their range of biodegradation rate still cannot satisfy the requirement for biodegradable biomaterials. The degradation rate of the biomaterials should not exceed remodeling rate and bone ingrowth. Therefore, biphasic calcium phosphate, the combination of HAp, TCP may present a scope for optimal biodegradable calcium phosphates, were developed. For these materials constituted of HAp and TCP mixture, the adjustment of Ca/P ratio value allows controlling the resorption rate. The combination of HAp, TCP can improve the mechanical properties, induce the proper biodegradation and promote the osteointegration that is increasing the bioactivity [2, 3, 6, 7]. Recent advancements in nanoscience and nanotechnology, investigation of nanoscale calcium phosphate has been revitalized because of its good biocompatibility and bone integration ability. Due to greater surface area which may improve fracture toughness, nano calcium phosphate powders exhibit improved sinterability and enhanced densification. Nevertheless, having better bioactivity, its particles can be utilized for engineered tissue implants with improved biocompatibility over other implants [8]. However, to effectively control the size and morphology of the resulting nanoparticles can be a hindrance. One of the solutions for this problem is to use ultrasonic irradiation, and its preferably used for many reasons: (1) increasesreaction speed, (2) decreases processing time, and (3) an overall improvement in the efficiency of energy consumption. The particle size relates to nucleation and the growth pattern of the material. Ultrasonic irradiation is used in the synthesis process promote both physical effects and chemical reactions that directly influence the synthesis procedure of materials in liquid [9]. In this research,BCP nanopowder were prepared by wet precipitation method under ultrasonic irradiation. The influences of pH of the starting solution on BCP microstructures and crystal structures were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FT- IR). 2. MATERIAL AND METHODS 2.1 Material Calcium chloride dihydrate (CaCl 2 .2H 2 O, 99%), tri-sodium phosphate dodehydrate (Na 3 PO 4 .10H 2 O, 98%) and sodium hydroxyte were obtained from Merck, Germany. 2.2 Experimental procedure Calcium chloride dihydrate and tri-sodium phosphate dodehydrate as calcium and phosphorous precursors were weighed to coincide the stoichiometric BCP with molar ratio of Ca/P = 1.57. Calcium phosphates were synthesized in aqueous solutions with constant pH at 50 o C. The pH of the system was maintained by adding of sodium hydroxide solution. A white precipitate was formed and the suspension was kept under ultrasonic irradiation for 1 h. After cooling to room temperature, the precipitate was washed thoroughly with de- ionized water several times and dried in an oven at 90◦C. Finally, the calcination was carried out at 750 ◦C in air. 2.3 Characterization The influence of pH on BCP nanopowder’s phase was identified using X-ray diffractometer (XRD, D8/Advance, Bruker, UK) with CuKα, (λ=1.5406 Å) as a radiation source over the 2θ range of 20 - 80º at 25ºC. Morphology and microstructure of the synthesized powders were investigated using FESEM (JSM-635F, JEOL). Infrared spectra were performed by FTIR (Equinox 55, Bruker, UK) in range of 400– 4000 cm -1 wave number region. For infrared spectroscopy, samples were pulverized and mixed with a given amount of potassium bromide (KBr) and pressed in very thin tablets. 3. RESULTS AND DISCUSSION Fig. 1 FESEM images of BCP and HAp nanopowders depending on the pH of the starting solution: (a,d) pH 7, (b, e) pH 9 and (c, f) pH 11 The morphology of synthesized BCP and HAP powders were shown in Fig 1. Both of them are nano particles which distribute uniformly. The particle size is related to nucleation and growth pattern of the material that is highly influenced by the degree of super saturation in the liquid phase. These effects increase chemical and physical effects, thus ultrasound can be used for the synthesis of materialsin liquid phase. Nano calcium phosphate, having better bioactivity, its particles can be utilized for biomaterial with improved biocompatibility. Fig. 2 XRD patterns of BCP and HAp nanopowders depending on the pH of the solution: (a) pH 7, (b) pH 9 and (c) pH 11. XRD spectra of the synthesized BCP and HAP nano powders are shown in fig 2. These graphs allowed calculating the Ca/P ratio of precipitated powders and the proportion of TCP (Table 1). Because of partial peak superposition, it appears that the most appropriate peaks for quantitative analysis correspond to the plane (2 1 0) at 2θ = 29° for HAP and to the plane (0 2 10) at 2θ = 31° for TCP. Therefore, the intensity ratios are used for quantitative analysis of biphasic calcium phosphates containing HAP and TCP [10]. They are defined as follows: R = 𝐼 𝑇𝐶𝑃 (0210 ) 𝐼 𝐻𝐴𝑝 (210) R  C  wt% TCP where C is a constant. Table 1: Synthesis parameters and compositions of BCP and HAp pH R 7 2,4 9 1,6 11 0 The intensity ratios of the plane (2 1 0) at 2θ = 29° for HAP and to the plane (0 2 10) at 2θ = 31° for TCP (R) decreased as the pH of the solution increased. The XRD pattern in Fig. 2 indicated that the sample (a) and (b) contained two crystalline phases (tricalcium phosphate and hydroxyapatite). On the other side, HAp existed in the sample (c), at pH 7 and 9 the synthesized powder shown mixed phases with TCP and HAp. On the other hand, at pH 11, the TCP phase disappeared due to its high solubility. Increasing the pH value caused the yield of TCP powders to gradually decrease [11, 12]. Fig. 3 FTIR spectrum of BCP and HAp nanopowders depending on the pH of the solution: (a) pH 7, (b) pH 9 and (c) pH 11. Fig. 3 shows typical FT-IR spectra of nano powders.The sharp peak at 3573 cm- 1 corresponds to the vibrations of the lattice OH – ions in HAp. The peak at 635 cm- 1 is stretching vibration of the HAp hydroxyl group. The very strong bands at 1032 cm -1 and 1092 cm -1 correspond to the PO 4 -3 functional group. The observation of the asymmetric P-O stretching vibration of the PO 4 3- bands at 962 cm -1 as a distinguishable peak, together with the sharp peaks at 635, 603 and 570 cm -1 correspond to the triply degenerate bending vibrations of PO 4 in hydroxyapatite. Our FTIR results were similar to the literature data [9, 13, 14]. 4. CONCLUSIONS In this study, the synthesis of nano HAp and BCP powder obtained by untrasound assisted process. The sample prepared at pH 7 and 9 is BCP powders, where-as the powder prepared at pH 11 had HAp powders. Thus, our results confirmed that increasing pH changed phase composition of the synthesized powders. The intensity ratios of the plane (2 1 0) at 2θ = 29° for HAp and to the plane (0 2 10) at 2θ = 31° for TCP (R) decreased as the pH of the solution increased since the TCP phase disappeared due to its high solubility. The prepared powders could be widely used for biomedical applications. REFERENCES 1. Engin N., and Tas A. -Manufacture of macroporous calcium hydroxyapatite bioceramics. J Eur Ceram Soc 19 (1999) 2569–2572. 2. 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Processing and Application of Ceramics 5 (2011) 193–198. 13. Jalota S., Tas A. C., and Bhaduri S. B. -Microwave-assisted synthesis of calcium phosphate nanowhiskers. J. Mater. Res 19 (2004) 1876-1882. 14. Zhou H., Lee J. -Nanoscale hydroxyapatite particles for bone tissue engineering. Acta Biomaterialia 7 (2011) 2769–2781. . SYNTHESIS NANO BIPHASIC CALCIUM PHOSPHATE BY UNTRASOUND ASSISTED PROCESS FOR BIOMATERIAL APPLICATION Ngoc Quyen Tran 1 , Cuu Khoa Nguyen 1 . phosphates is a promising material for biomedical applications. Biphasic calcium phosphate nanopowders (mixture of Hydroxyapatite and tricalcium phosphate) were prepared by precipitation method under. thái của nano BCP được xác định bằng phương pháp kính hiển vi điện tử quét (SEM). Từ khóa: biphasic calcium phosphat, calcium phosphate, sóng siêu âm Abstract Nanoscale calcium phosphates