Gel behavior of composite hydrogel of alginate and gelatin and its application as scaffold for bone tissue

• Main Authors: Yu-ju Tzeng, 曾鈺筑
• Other Authors: Ming-chien Yang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/88074524339419240912

碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 100 === An in situ injectable hydrogel made of sodium alginate and gelatin was prepared to study the feasibility for bone tissue engineering. Base on the temperature-sensitivity of gelatin, which was loaded with calcium ions, the time of sodium alginate was extended until reaching body temperature. In addition, cells were encapsulated with gelatin to avoid the damage during gelation and to facilitate the cells by injection into the bone defect. Rheometer and differential scanning calorimeter (DSC) were employed to determine the effect of doping the calcium ion in gelatin on the melting temperature (Tm) of gelatin. Transmission electron microscope (TEM) was used to determine the effect of citric acid as dispersant for hydroxyapatite (HAp). Rheometer was also employed to detect the gelation of alginate scaffold via temperature-scanning. The biocompatibility of scaffold was evaluated with osteoblast (hFOB 1.19) as the representative of the affected area, fibroblasts (L-929) as the representative of the surrounding tissue. According to ISO 10993-5, the in vitro cytotoxicity test was based on culturing cells with the extract of test samples. The effect of encapsulation was investigated by the proliferation of encapsulated cells and free cells on the scaffold. The functionality of osteoblast was observed by the alkaline phosphatase (ALPase) activity and protein production. The results showed that by mixing calcium chloride, Tm of gelatin was decreased with the increase of the content of calcium chloride. The presence of HAp didn’t affect the Tm of gelatin. However, by using citric acid as the dispersant, the Tm of gelatin decreased with the concentration of citric acid. The TEM micrographs showed that the size of HAp was reduced from 2μm to 100 nm by 2.5 % citric acid. The result of rheometer show that when calcium-loading gelatin beads contacted with sodium alginate, the elasticity of the gel increased with the ratio of calcium loading gelatin. Thus using the gelatin as the calcium ions carrier can effectively extend the gelation time of alginate by 15 min, which would be useful for processing and shaping when administration. The in vitro cytotoxicity test showed that the extract of HAp-loading gelatin beads without crosslinking with alginate seemed not suitable for L-929 to grow. Furthermore, hFOB 1.19 seemed sensitive to the environment: although the samples extracts caused death to part of cells, the survivors could still grow with time. The cell encapsulated carrier is good for cell to adhere on the unstable surface, but the process of encapsulation is not good for hFOB 1.19 to survive. The hFOB 1.19 growing on the scaffold can express ALPase activity and produce proteins, suggesting this scaffold can promote the initial differentiation of hFOB 1.19. Thus the scaffolds have the potential to become the bone tissue engineering scaffolds.