基于纳米氧化石墨烯载体共载替莫唑胺及化疗增敏剂O6BG协同靶向治疗胶质瘤的研究

Temozolomide（TMZ）is a widely used chemotherapeutic agent for glioma, but only about 45% patients with glioma are sensitive to such drug. TMZ cytotoxicity is primarily mediated through O6-MeG. Direct repair of O6-MeG by the suicide enzyme methylguanine-DNA methyltransferase (MGMT) removes the methyl adducts to restore guanine, and such DNA repair mechanism contributes to TMZ resistance. O6-benzylguanine (O6BG), a low-molecular-weight substrate, can irreversibly inactivate MGMT. A problem encountered in the systemic application of O6BG clinically is that MGMT depletion in normal tissue cells also sensitizes them to be injured by TMZ. Nanoscaled grapheme oxide (nGO) is a two-dimensional nanomaterial, and its good biocompatibility without obvious toxicity makes it a promising drug carrier. Our previous study showed that micromolecule chemotherapeutic agent could be transferred into glioma cells after loaded onto nGO modified with transferrin(Tf), leading to better prognosis. Furthermore, both TMZ and O6BG could be loaded onto nGO separately in our preliminary experiment, and the releasing rate of O6BG is much higher than TMZ. On basis of such principles, a new kind of drug carrier system with TMZ and O6BG co-loaded onto nGO modified with Tf was designed, for the purpose of transferring TMZ and O6BG into glioma cells targetedly. Furthermore, such nano-carrier system was estimated its glioma-targeting property and releasing O6BG and TMZ sequentially to anti-tumor effectively via fluorescent tracer technique and HPLC qualitatively and quantitatively. Moreover，such research may provide perspectives for anti-chemoresistance of glioma.

替莫唑胺（TMZ）抗胶质瘤有效率仅为45%，TMZ耐药与MGMT密切相关，O6BG能抑制MGMT活性而增强TMZ的抗肿瘤效果，但也增强TMZ的副作用。我们前期研究证实：TMZ及O6BG能分别高效负载到纳米氧化石墨烯（nGO）这一具有良好生物安全性、高效药物载体上,且O6BG的释放速度明显快于TMZ。本研究拟将nGO经转铁蛋白(Tf)这一具有胶质瘤靶向性的配体修饰后，同时负载TMZ及O6BG。以期在Tf的介导下靶向转运TMZ及O6BG到胶质瘤部位，先释放出O6BG，使之阻断MGMT的活性后再释放TMZ，增强TMZ抗肿瘤效应。在胶质瘤细胞及荷瘤大鼠模型上，通过荧光示踪、高压液相色谱分析等方法定性、定量证实该纳米载药系统具有胶质瘤靶向性，并实现O6BG及TMZ序贯释放达到协同化疗目的，同时在分子水平探讨其抗耐药机制，有望对TMZ耐药的胶质瘤化疗提供新的思路。

替莫唑胺（TMZ）是目前广泛应用于临床的抗胶质瘤的药物，但其有效率仅为45%，并且耐药性有逐渐提高的趋势。MGMT与TMZ耐药密切相关，O6BG是MGMT的抑制剂,在增强TMZ的抗肿瘤效果的同时也抑制正常细胞的MGMT活性，使TMZ的副作用上升。我们研究证实：TMZ及O6BG能分别高效负载到纳米氧化石墨烯（nGO）这一具有良好生物安全性、高效药物载体上,且O6BG的释放速度明显快于TMZ；二者的载药量及分别达到45.25%及12.78%，TMZ/O6BG为3.52.。此外，转铁蛋白（Tf）共价连接到nGO后，在Tf的介导下能将小分子化疗药靶向转运到胶质瘤细胞内增强疗效。本研究将nGO经Tf修饰后，同时负载TMZ及O6BG，在胶质瘤细胞系C6、U87MG及荷瘤大鼠模型、荷瘤裸鼠模型上通过荧光示踪、高压液相色谱分析等方法定性、定量证实该纳米载药系统具有胶质瘤靶向性，并实现O6BG及TMZ序贯释放达到协同化疗目的，并在分子水平探讨其抗耐药机制，本研究可能为对TMZ耐药的胶质瘤化疗提供新的思路。