Biodegradability and cytocompatibility evaluation of surface modified calcium hydrogenphosphate
Other Title
表面改質之磷酸氫鈣其生物降解性及細胞穩定性之評估
Journal
Journal of Medical and Biological Engineering
Journal Volume
21
Journal Issue
4
Start Page
249
End Page
256
Date Issued
2001
Author(s)
Abstract
Much effort has been directed to the development of osteoconductive and osteoinductive materials for bone substitutes by the addition of polypeptides or protein factors to carrier. In a viewpoint for prolonging acceleration of bone defect healing, it was necessary to reinforce the bonding strength of the interface between carrier and growth factor. Chemical immobilization was a very suitable way. Before immobilization of growth factor, to improve the surface properties of carrier was of the first importance. From our study, the surface of calcium hydrogenphosphate (CaHPO4, CHP) has been successfully modified by Hexamethylene diisocyanate (HMDI). It was proved that CHP bridged with HMDI molecule through a urethane linkage and would leave an amine group in the tail after modified. The HMDI-surface-modified CHP is as so-called MCHP. Before further use, the biodegradability and cytocompatibility of MCHP was interested. In this study, we utilized the release solution, which was obtained from immerse MCHP powder into phosphate buffer solution (PBS) at 37℃ for 56 days, as culture medium to assay the activity of rat osteoblasts. After culturing for 2 days, the activity of osteoblasts was determined using a specific enzyme-linked immunosorbent assay (ELISA). The reduction of relative activity would be associated with the cytotoxicity of MCHP. In addition, the biodegradability of MCHP was described by evaluating its solubility. Atomic absorption spectrum was powerful to determine the amount of calcium in release solution. Our results showed that MCHP was still biodegradable. The HMDI-modification doesn't influence MCHP to release calcium ion. However, during degradation some cytotoxic substance was also released through ionization of MCHP, hydrolysis of urea or urethane linkage. The amount of toxic product, HMDA, was measured to be with 25% of grafted-HMDI. The cytotoxicity of MCHP was still maintained after 56-days soaking in physiological environment. In spite of that, we believed that the toxic product could be removed completely by appropriate pretreatment. Results showed that the cytotoxicity of MCHP was eliminated through hydrolyzing MCHP at higher temperature for 4 days.
近年來，合成的骨替代材料廣泛被發展，而當前更以開發兼具骨誘導性及骨引導性的材料為首要。目前研究顯示藉由添加polypeptides或蛋白質因子於載體中將可呈現骨引導的現象，然而其作用期極短，為了延長此類促進因子於修復骨缺陷的療效，直接強化載體與生長激素間的鍵結強度被認為將是最有效的方法，而化學固定將是較適當的，因為藉由化學鍵於兩者間形成不但可有效將生長激素固定於載體，更因為共價化學鍵結的存在使其可以穩定存在於載體表面，以供長期治療骨修復之用。但又由於陶瓷載體之化學反應性低，因此改善載體的表面性質將是首要任務。從我們先前的研究顯示，藉由二異氫酸己烷(hexamethylene diisocyanates; HMDI)與磷酸氫鈣(calcium hydrogenphosphate; CHP)的作用，我們可有效改善磷酸氫鈣的表面性質，並且已證實二異氫酸己烷將藉由氨基甲酸酯鍵結(urethane linkage)穩定固定於磷酸氫鈣表面，於主鏈尾端將以胺基型態存在，此二異氫酸己烷表面改質之磷酸氫鈣被簡稱為MCHP。MCHP被近一步使用之前，其生物降解性及細胞穩定性將倍受重視。在本研究中，我們將MCHP浸泡於磷酸緩衝溶液中，於37℃下持續浸泡56天，收集各期浸泡液與骨母細胞作培養，與釋放液培養兩天後將利用特定的酵素免疫吸收法(ELISA)評估骨母細胞之活性變化；假若骨母細胞之相對活性下降則可評估可能為MCHP的毒性所造成。此外，MCHP的生物降解性將藉由其解離度來評估，利用原子吸收光譜我們將準確偵測出釋放液中鈣含量，並藉此了解鈣釋放的情形以作為MCHP生物降解性的探討。由實驗結果顯示，MCHP依舊是生物降解性材料，二異氫酸己烷的改質將不影響其釋放鈣離子。降解過程中仍然可能釋放了一些細胞毒性物質，此毒性物質乃經由MCHP的解離、尿素或氨基甲酸酯鍵結的水解。其毒性物為己二胺，經評估固定於MCHP表面之二異氫酸己烷有25%將以己二胺型態釋放出來，此細胞毒性即使經過56天於生理環境下浸泡都無法去除。我們相信適當的前處理將可去除MCHP的細胞毒性。研究中我們利用MCHP於高溫下的水解作用，順利的將MCHP細胞毒性給去除。
Subjects
CaHPO4
Cytocompatibility
Biodegradability
Cytotoxicity
磷酸氫鈣表面改質
細胞穩定性
生物降解性
細胞毒性
Type
journal article