近年來磁振造影(Magnetic Resonance Imaging,MRI)已被發展至應用於人體到細胞及分子的層級,為了完全開發MRI技術應用於細胞、分子與功能性影像,能夠標幟活體細胞的目標化、區域化、量化及功能之新一代MRI對比劑與技術是目前迫切需要。在臨床上,賀癌平(Herceptin)被用於HER2/neu基因過度表現型乳癌之治療,依其作用機制,亦可做為探針用以偵測HER2/neu基因過度表現的細胞或腫瘤。本研究設計及合成超順磁氧化鐵奈米粒子(superparamagnetic iron oxide nanoparticles,SPIO)作為核心,包覆糊精(dextran)增加其生物相容性及水溶性,並鍵結抗癌藥物Herceptin以期達到標效果(CLIO-Herceptin)。在本實驗中利用傅立葉轉換紅外光譜儀(FT-IR)、熱分析(TGA)證實對比劑確實成功合成,經由穿透式電子顯微鏡觀察且得知氧化鐵奈米粒子分散良好且無聚集現象,並得氧化鐵奈米粒子平均粒徑大小約為3.5 ± 0.8 nm。藉由超導量子干涉儀(SQUID)量測CLIO-Herceptin得知其具有超順磁性、高飽和磁化率(80emu/g)及無磁滯現象。長時間量測弛緩率及利用粒徑分析儀(DLS)量測水合粒徑,由結果可發現,長時間擺放並不會造成聚集現象,表示CLIO-Herceptin具有良好的穩定性。在細胞毒性實驗中發現,高濃度CLIO-Herceptin培養下,細胞存活率仍達60%,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)結果顯示,不同HER2/neu基因表現量的實驗組細胞株,其訊號對比程度表現亦不相同,細胞膜上表現愈多HER2/neu基因受器,其訊號愈顯著下降,而控制組細胞株影像上無明顯變化,表示CLIO-Herceptin可藉由受器媒介進而鍵結在細胞膜上。在體內(in vivo)實驗研究中,將兩株實驗組及控制組細胞株,即表現及不表現HER2/neu基因(SKBR-3及KB細胞株),接種於無特定病源裸鼠(nude mice)後腿上方之兩側,在獲得動物模型後,再由尾部靜脈注射CLIO-Herceptin (20μmol/kg),以3.0 Tesla MR scanner進行造影,由影像發現注射對比劑後,SKBR-3腫瘤有變黑的現象,量測且計算其訊號變化,大約下降45%,由體內影像結果得知,本實驗合成的對比劑確實有目標化的功能。
Magnetic resonance (MR) tracking of superparamagnetic iron oxide (SPIO)-labeled cells is a relatively new technique to non-invasively determine the cancer cells. A new magnetic resonance imaging (MRI) contrast agent containing Herceptin was synthesized and reported. The surface of superparamagnetic iron oxide nanoparticles ?vSPIO?w were modified with dextran and conjugated with Herceptin (CLIO-Hercetpin) to improve their dispersion, magnetization and ability to target specific receptors of cells. From the results, we found that the CLIO-Herceptin had well-dispersed in different pH value solutions, no hysteresis, high saturation magnetization (80 emu/g) and low cytotoxicity of different cell lines. The results of in vitro imaging noteworthy that the MR enhancement for the different breast cancer cell lines (BT-474, SKBR-3, MDA-MB-231 and MCF-7) are proportion to the HER2/neu expression level. When the CLIO-Herceptin was administered to breast tumor allograft mice by intravenous injection, the tumor site was patently detected in T2-weighted MR images as a 45 ?s enhancement drop indicating a high level of accumulation of the contrast media within the tumor site. Targeting of CLIO-Herceptin into targeted cells was observed by in vitro and in vivo MR imaging studies.