Preparation of chitosan-HAp composite fiber for artificial ligament

Abstract

Event Abstract Back to Event Preparation of chitosan-HAp composite fiber for artificial ligament Takuma Okada1, Toshiki Miyazaki1*, Yuta Nobunaga2*, Toshiisa Konishi2*, Tomohiko Yoshioka2*, Satoshi Hayakawa2* and Yuki Shirosaki3* 1 Kyushu Institute of Technology, Graduate School of Life Science and System Engineering, Japan 2 Okayama University, Graduate School of Natural Science and Technology, Japan 3 Kyushu Institute of Technology, Frontier Research Academy for Young Researchers, Japan Introduction: Although autograft is clinically used for reconstructive surgery of anterior cruciate ligament, it has still some problems. For example, it is necessary to extract the ligament tissue from other healthy part of patient’s body[1][2]. This problem can be solved by using artificial ligament. For this purpose, we focus on chitosan and hydroxyapatite (HAp) composite fiber. Chitosan is biodegradable polymer and HAp is fundamental inorganic component for exhibiting bone-bonding ability. Therefore we expect that the composite fiber can bond to bone and play a role as a scaffold for ligament tissue regeneration. Tamura et al., reported that the chitosan-HAp fiber can be prepared by coagulation system using calcium chloride solution[3]. This method is suitable for biomaterial fabrication because of synthesis with low toxicity materials. However, the obtained fiber did not have sufficient mechanical strength for artificial ligament, since excessive calcium ion decreased crystallinity of chitosan. In this study, we attempted sodium hydroxide treatment of the chitosan fiber containing phosphate ion to form HAp on the fiber and remove the excessive calcium ion and acetic acid. Materials and Methods: Chitosan solution was prepared by dissolving 10.5 g of chitosan powder and the appropriate amount of sodium dihydrogen phosphate in 30 mL of 0.1 M acetic acid solution. The solution was pumped into coagulation bath from nozzle with hole 0.5 mm in diameter. Coagulation bath was prepared mixing the saturated calcium chloride aqueous solution and ethanol. The wet fiber was soaked in ethanol for 5 min, and subsequently soaked in 0.2 M sodium hydroxide solution for 30 min to remove the excessive calcium ion and acetic acid. The fiber was then stretched by two rollers at speed ratio of 2:3. Finally, the fiber was dried at room temperature. The structure of the fiber was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Tensile strength of the fiber was measured by Creep meter. The fiber was soaked in simulated body fluid (SBF) for 3 days to examine apatite growth. Results and Discussion: Although HAp formation on the fiber was not confirmed just after the coagulation by XRD, HAp was formed after the subsequent sodium hydroxide treatment. Assemble of HAp nanoparticle was observed on the surface of the fiber by SEM. In addition, crystallinity of the chitosan was improved by the treatment. After soaking in SBF, intensity assigned to HAp in XRD pattern was increased. Tensile strength of the fiber showed tendency to increase with increase in crystallinity of the chitosan. It is assumed that calcium phosphate in the fiber transforms to HAp and excessive calcium ion chelated with carbonyl group of chitosan is removed by sodium hydroxide treatment. Therefore a lot of hydrogen bond is constructed between amino group and carbonyl group of chitosan. Consequently crystallinity and tensile strength are improved. Conclusion: Chitosan-HAp composite fiber was obtained by coagulation method. Sodium hydroxide treatment after the coagulation was effective for enhancement of not only HAp precipitation but also mechanical property. It is expected that the obtained fiber is suitable for artificial ligament.