超順磁性奈米粒子 MnFe2O4-Erbitux 之合成、特性

Abstract

磁振造影技術(Magnetic Resonance Imaging，MRI)經過多年的發展，已經開始進入應用在細胞甚至分子層級。藉分子影像技術發展出的藥物也如預期能達到具專一性治療效果及降低治療藥物在生物體系統內的毒性。為了在更小的層級下開發應用於細胞與功能性的影像，達到標幟活體細胞的目標化、區域化和量化的新型對比劑之開發和設計是不可或缺的。在臨床上，Erbitux 被用於治療上皮成長因子受體高度表現(EGFR-expression)的腫瘤細胞，依其作用機制，亦可作為探針用以偵測EGFR過度表現的細胞或是腫瘤。本研究利用熱裂解方式，合成了超順磁氧化鐵奈米粒子(superparamagnetic iron oxide nanoparticles, SPIO)，並嘗試利用參雜(doping)的形式，以求得更高的T2弛緩率。合成出的奈米粒子，將其包覆為MnFe2O4-PEG-NH2，利用修飾後的聚乙二醇(PEG-NH2-silane)包覆，藉以增加其水溶性和生物相容性。在細胞毒性實驗中發現，高濃度MnFe2O4-Erbitux培養 下，細胞存活率並沒有明顯的下降，推測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EGFR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 EGFR，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MnFe2O4-Erbitux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(SKBR-3 及 COLO-205)，即表現及不表現 EGFR，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MnFe2O4-Erbitux (15μmol/kg)，以 3.0 Tesla MR scanner進行造影，由影像發現注射對比劑後，A431腫瘤有變黑的現象，量測並且計算其訊號變化，大約下降23%，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。

Molecular imaging has recently been developed very rapidly and extensively in biotechnology. Tumor-targeted drug delivery can enhance the effectiveness of therapy while decreasing the systemic toxicity of these drugs. A new magnetic resonance imaging (MRI) contrast agent containing Erbitux was synthesized and reported. Recent investigations show that manganese doped superparamagnetic iron oxide (MnFe2O4) nanoparticles have higher T2 relaxivity and magnetization than those of iron oxide (Fe3O4) nanoparticles. Therefore, the manganese ferrite nanoparticles (MnFe2O4) were synthesized by thermal decomposition to get higher T2 relaxivity and enhance the negative enhancement. The MnFe2O4 nanoparticles were synthesized and coated with polyethylene glycol (PEG), which has been frequently used as a drug carrier because of its biocompatibility, water solubility, low cytotoxicity, and their ability to escape capture by macrophages. The results of in vitro MR imaging indicated that the negative enhancement of the different cancer cell lines (A431, SKBR-3, PC-3, and COLO-205) are correlated to the EGF receptor expression level. The MnFe2O4-Erbitux nanoparticles were administered to high EGF receptor expression tumor allograft mice by intravenous injection, and the positive tumor was patently detected in T2-weighted MR images as a 23 % enhancement drop indicating a high level of accumulation of the contrast media within the positive tumor. Therefore, targeting of MnFe2O4-Erbitux nanoparticles into positive cells was observed by in vitro and in vivo MR imaging studies.