血管內皮生長因子抗體鍵結氧化鐵奈米粒子在活體腫瘤中的標靶及造影

Abstract

磁性氧化鐵奈米粒子對生物具有低毒性、高生物降解率、可穩定存在於循環中等性質，藉由在奈米粒子表面修飾加上腫瘤標靶物質，可以用來追蹤腫瘤位置，協助診斷。血管內皮生長因子在許多不同的腫瘤中皆有高度表現，使其成為一個可行的標靶目標，因此我們針對血管內皮生長因子設計出可標靶的氧化鐵奈米粒子(vascular endothelial growth factor antibody conjugated iron oxide nanoparticles，VEGF-NP)來達到腫瘤標靶的目的。為了測試此奈米粒子在循環後到達腫瘤中的分布情形，將帶有表達VEGF的小鼠大腸癌細胞CT26植入BALB/c小鼠，再經由頸靜脈注射給予VEGF-NP，由核磁共振(magnetic resonance imaging，MRI) 做觀察。結果顯示在給予VEGF-NP的組別可顯著的縮短T2遲緩時間使得T*2訊號降低，在MRI下呈黑色顯影。進一步以普魯士藍染色法，其實驗結果顯示，給予VEGF-NP的組別，在腫瘤組織切片中有強烈的藍色反應，表示有大量的VEGF-NP聚積在腫瘤中。另外在穿透式電子顯微鏡結果中也發現，給予VEGF-NP的組別，腫瘤細胞或細胞外基質也可觀察到奈米粒子。目前我們的研究結果顯示，VEGF-NP經過體循環後，不易被網狀內皮系統(reticuloendothlial system）清除，仍可以大量聚集到腫瘤組織中，顯著增強MRI的造影，以利判別腫瘤位置，未來可作為一個診斷腫瘤的重要輔助工具。

Magnetic iron oxide (IO) nanoparticles with a long blood retention time, low toxicity, and biodegradability can be engineered to link tumor-targeting ligands for diagnostic imaging. Upregulation of vascular endothelial growth factor (VEGF) is found in many cancer types, which provides an opportunity for designing antibody-targeted approaches for cancer detection and treatment. To determine if the systemic delivery of nanoparticles leads to target specific accumulation into the VEGF-expressing tumor mass in vivo, we injected the VEGF Ab-conjugated IO nanoparticles, which have the superparamagnetic property, through the jugular vein into the balb/c mice bearing colon cancer from the VEGF-positive mouse colon cancer cell line, CT 26. Magnetic resonance imaging (MRI) scan showed the significant decrease of significant T*2 signal and T2 relaxation in the VEGF Ab conjugated IO nanoparticles injected-mice but not in IO nanoparticles-treated mice. Examination of paraffin sections of tumor tissues revealed strong blue reaction obtained from the mice that received VEGF Ab conjugated nanoparticles, but low reaction was found in mice with IO nanoparticles alone injection by Prussian blue staining. A lot of VEGF Ab-conjugated IO nanopartices were present in cells and extracellular matrix in tumor tissues than IO nanoparticle-injected mice by transmission electron microscopy. The present study demonstrated that efficient accumulation of VEGF Ab conjugated IO nanoparticles into tumor cells after systemic delivery. These results suggested that VEGF Ab conjugated IO nanoparticles can be used for the targeted delivery of therapeutic agents.