Ultrastructure of a Carbon Nanotube-based Delivery System for Cancer Therapy

碳纳米管具有附着药物和定向配体，具有良好的靶向药物递送潜力。具有很高比表面积的单壁碳纳米管（SWNT）可以通过化学附着、吸附或包封与生物分子衍生化。这种单壁碳纳米管上的生物偶联物具有将生物活性分子传递穿过细胞膜甚至进入细胞核的能力。我们进行了超微结构实验，研究功能化碳纳米管在口腔癌细胞输送治疗药物中的应用。抗癌药物顺铂与单壁碳纳米管（SWNTs）共价结合，而这些碳纳米管又与表皮生长因子（EGF）结合，而表皮生长因子在口腔癌细胞中表达得非常高。经戊二醛和四氧化二锇固定，脱水后包埋于epon中，制备的头颈部鳞状细胞癌（HNSCC）上皮细胞经功能化纳米颗粒孵育后的电镜观察。使用120千伏透射电镜记录的电子显微照片显示，成束的单壁碳纳米管已经进入细胞。在大多数HNSCC细胞中，SWNT束分布在细胞质中，而一些细胞在细胞核附近显示出更高浓度的纳米管。结果证实了共聚焦荧光显微镜获得的较低分辨率数据，但提供了更详细的关于纳米管进入后与亚细胞结构相关的信息。在NIDCR中，超微结构数据与光学测量和细胞活力测定相关联。我们还使用扫描透射电子显微镜（STEM）和x射线纳米分析来表征单个纳米管并确定结合铂原子的分布。表征这些纳米颗粒生物偶联物对该方法的未来发展至关重要。特别是，纳米管的尺寸和每纳米管长度的生物分子数量是重要的参数，特别是对于药物输送。我们的STEM研究结果首次显示了附着在单壁碳纳米管上的基于pt的药物分子的原子尺度可视化和定量。

Carbon nanotubes with attached drugs and directing ligands have excellent potential for targeted drug delivery. Single wall carbon nanotubes (SWNT) with very high specific surface areas can be derivatized with biomolecules either through chemical attachment, adsorption or encapsulation. Such bioconjugates on SWNTs have the ability to deliver bioactive molecules across cell membranes and even into cell nuclei. We have performed ultrastructural experiments to investigate the application of functionalized carbon nanotubes to deliver therapeutic drugs to oral cancer cells. The anti-cancer drug cisplatin was covalently bound to single walled carbon nanotubes (SWNTs) and these were in turn bound to epidermal growth factor (EGF), which is expressed at very high levels by oral cancer cells. Cultured head and neck squamous cell carcinoma (HNSCC) cells of epithelial origin incubated with the functionalized nanoparticles were prepared for electron microscopy by fixation in glutaraldehyde and osmium tetroxide, followed by dehydration and embedding in epon. Electron micrographs, recorded digitally using a 120 kV TEM, revealed that bundles of SWNTs had entered the cells. In most HNSCC cells the SWNT bundles were distributed throughout the cytoplasm, whereas some cells showed a higher concentration of nanotubes adjacent to the cell nucleus. The results confirmed lower resolution data obtained from confocal fluorescence microscopy but provided more detailed information about the subcellular structures associated with the nanotubes after entry. The ultrastructural data are being correlated with optical measurements and cell viability assays conducted in NIDCR. We have also used scanning transmission electron microscopy (STEM) and x-ray nanoanalysis to characterize individual nanotubes and to determine the distribution of bound platinum atoms. Characterization of these nanoparticle bioconjugates is essential for the future progress of this approach. In particular, nanotube size, and number of biomolecules per nanotube length are important parameters, especially for drug delivery. Our STEM results show for the first atomic scale visualization and quantification of single Pt-based drug molecules attached to SWNTs.