- 學位論文
具目標化之磁振造影對比劑Gd-NP-TTDA-BN 及Gd-NB-TTDA-IL11 之合成及特性研究
Synthesis and Characterization of Gd-NP-TTDA-BN and Gd-NB-TTDA-IL11 as the Targeting MRI Contrast Agents
摘要
蛙皮素(bombesin，BN)是一段由14個胺基酸所組成的胜肽，其受體 家族之一的胃泌素胜肽受體(Gastrin-releasing peptide receptor，GRPR)以被證明過度表現於多種的癌細胞上。在這個研究中，我們設計合成了雙功能對比劑Gd-NP-TTDA-BN-Cy5.5，希望可以應用在磁振造影及光學影像上。Gd-NP-TTDA-BN在20 MHz、37.0 ± 0.1 ?aC下，求得其弛緩率（r1為7.12 mM-1s-1。在細胞毒性實驗中發現，在高濃度Gd-NP-TTDA-BN培養下，細胞存活率仍達80%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。由體外(in vitro)MRI 結果顯示，Gd-NP-TTDA-BN增加了GRPR過度表現的PC-3細胞的對比，而對照組細胞株影像上無明顯變化，表示Gd-NP-TTDA-BN可藉由受器媒介進而鍵結於前列腺癌細胞，優於臨床上使用的MRI對比劑[Gd(DTPA)]2-。在體內(in vivo)實驗研究中，Gd-NP-TTDA-BN可目標化至PC-3腫瘤且提高其訊號強度，而使腫瘤位置容易辨別。細胞螢光標的實驗結果可發現Gd-NP-TTDA-BN-Cy5.5 可目標化至PC-3前列腺癌細胞且有明顯的螢光表現，並且可由光學影像明顯的標的出裸鼠PC-3腫瘤細胞的位置並具有很高的靈敏度。Gd-NP-TTDA-BN-Cy5.5為雙功能目標化對比劑，可用於光學影像及MRI偵測胃泌素受體過度表現的腫瘤細胞。 另一方面，我們亦合成了可目標化乳癌細胞的雙功能對比藥劑 Gd-NB-TTDA-IL11，白介素11(interleukin 11)為一傳遞細胞訊息的激素，interleukin 11 與其受體interleukin -11 receptor alpha chain ( IL-11Ra在乳癌的骨轉移扮演了很重要的角色，c(CGRRAGGSC)為一由interleukin 11蛋白質序列中擷取可目標化至IL-11Ra的環狀的胜肽，與NB-TTDA 鍵結後合成其釓金屬錯合物。由細胞毒性實驗結果證實了Gd-NB-TTDA-IL11 低毒性，在體外磁振造影實驗證明可目標化至MDA-MB-231 乳癌細胞上而提升其訊號強度，增加MRI的對比效果。而在細胞螢光標的實驗也證明了Gd-NB-TTDA-IL11-Cy5.5 可目標化至IL-11Ra，此初步的結果顯示了這個雙功能的對比劑有潛力作為乳癌的診斷及追蹤。
並列摘要
This study describes the synthesis and preliminary biologic evaluation of a bombesin peptide targeted contrast agent as a potential probe for detecting human prostate cancer with magnetic resonance imaging (MRI). The bombesin peptide was synthesized and conjugated with the TTDA chelating moiety via solid-phase peptide synthesis, purified by reversed-phase HPLC,and characterized by mass.The T1 relaxivity of Gd-NP-TTDA-BN was 7.12 mM-1 s-1 at 37 ± 0.1°C and 0.47 T. The targeted contrast agent specifically bound to tumor tissue and resulted in significant tumor contrast enhancement at a dose of 0.1 mmol Gd/kg at least 60 min in mice bearing PC-3 human prostate carcinoma xenografts as shown in MR images. The preliminary results has shown that Gd-NP-TTDA-BN can specifically bind to gastrin-releasing peptide receptor in tumor tissue, resulting in significant tumor enhancement.On the other hand, we developed an optical and MRI dual-labeled imaging agent Gd-NB-TTDA-IL11-Cy5.5. The cyclic peptide c(CGRRAGGSC), which is known to target interleukin 11 receptor alpha-chain (IL-11R??), delivers the desired imaging agent to its target.The results revealed that the cyclic peptide c(CGRRAGGSC) continued to possess the targeting capability to breast cancer?n?nafter the conjugation of the optical and MRI contrast agent. Targeting of Gd-NB-TTDA-IL11-Cy5.5 into targeted cells was observed by in vitro MR imaging study and optical imaging. Gd-NB-TTDA-IL11 has low cytotoxicity and specific tumor localization. The preliminary results demonstrate that the bimodal IL-11 peptide analog can be used to detect IL-11R?? positive breast cancer with MRI and fluorescence microscope at the cellular level.