應用於Legumain 偵測之磁振造影對比劑 Gd-NBCB-TTDA-Legumain 之研究

Abstract

磁振造影是目前臨床醫學上常使用的診斷工具，不同於其他造影技術，其對軟組織的成像具有相當的效果，但靈敏度卻稍顯不足。因此本研究設計合成一條由8個胺基酸所組成的胜肽，其對Legumain酵素具有目標性，且在多種腫瘤上都有過度表現。並在胜肽N端鍵結NBCB-TTDA，形成對腫瘤組織中的Legumain具有專一辨識功能的磁振造影對比劑Gd-NBCB-TTDA-Legumain。在20 MHz、37.0 ± 0.1 °C下，Gd-NBCB-TTDA-Legumain所求得弛緩率(r1)為4.94 mM-1s-1。在T1弛緩時間變化量的實驗中發現，當有存在3T3-Legumain cell lysate時，T1約上升20 %。在細胞毒性實驗中發現，在高濃度(1 mM) Gd-NBCB-TTDA-Legumain培養下，細胞存活率仍達85 %以上，推測若以低劑量打入動物體內不具有抑制細胞生長的危險性。在體內(in vivo)實驗研究中，Gd-NBCB-TTDA-Legumain可目標化至CT-26腫瘤且提高其訊號強度，而使腫瘤位置容易辨別。結果顯示此磁振造影對比劑有潛力對有Legumain表現之腫瘤進行診斷及追蹤。

Magnetic resonance imaging (MRI) has become the leading tool for imaging and ability to resolve different soft tissues. MRI has not been effectively used for molecular imaging because of its low sensitivity. In this study, we designed and synthesized a novel contrast agent (CA), Gd-NBCB-TTDA-Legumain, to image the activity of asparaginyl endopeptidase, known as Legumain, in a tumor, noninvasively using MR imaging. The T1 relaxivity of Gd-NBCB-TTDA-Legumain was 4.94 mM-1 s-1 at 37± 0.1 °C and 0.47 T. Relaxometric studies shows that the percentage change in T1 value of Gd-NBCB-TTDA-Legumain under the different incubation time, increases 20 % in the presence of 3T3-Legumain cell lysate. The cytotoxicity results displayed that the cell viability was more than 85% after the incubation of cells for 24 h under high concentration of Gd-NBCB-TTDA-Legumain. The contrast agent would be specifically recognized by Legumain enzyme around the tumor tissue, which results in significant tumor contrast enhancement at a dose of 0.1 mmol Gd/kg for at least 60 min in mice bearing CT-26 murine colon carcinoma xenografts for MR images. Therefore, the Gd-NBCB-TTDA-Legumain can be potentially used as a contrast agent for cancer molecular imaging.