Department of Organic Chemistry, Indian Institute of Science, Bangalore, India.
Nanotechnology. 2012 Feb 17;23(6):065101. doi: 10.1088/0957-4484/23/6/065101.
Methods which disperse single-walled carbon nanotubes (SWNTs) in water as 'debundled', while maintaining their unique physical properties are highly useful. We present here a family of cationic cholesterol compounds (Chol+) {Cholest-5en-3β-oxyethyl pyridinium bromide (Chol-PB+), Cholest-5en-3β-oxyethyl N-methyl pyrrolidinium bromide (Chol-MPB+), Cholest-5en-3β-oxyethyl N-methyl morpholinium bromide (Chol-MMB+) and Cholest-5en-3β-oxyethyl diazabicyclo octanium bromide (Chol-DOB+)}. Each of these could be easily dispersed in water. The resulting cationic cholesterol (Chol+) suspensions solubilized single-walled carbon nanotubes (SWCNTs) by the non-specific physical adsorption of Chol+ to form stable, transparent, dark aqueous suspensions at room temperature. Electron microscopy reveals the existence of highly segregated CNTs in these samples. Zeta potential measurements showed an increase in potential of cationic cholesterol aggregates on addition of CNTs. The CNT-Chol+ suspensions were capable of forming stable complexes with genes (DNA) efficiently. The release of double-helical DNA from such CNT-Chol+ complexes could be induced upon the addition of anionic micellar solution of SDS. Furthermore, the CNT-based DNA complexes containing cationic cholesterol aggregates showed higher stability in fetal bovine serum media at physiological conditions. Confocal studies confirm that CNT-Chol+ formulations adhere to HeLa cell surfaces and get internalized more efficiently than the cationic cholesterol suspensions alone (devoid of any CNTs). These cationic cholesterol-CNT suspensions therefore appear to be a promising system for further use in biological applications.
方法，分散单壁碳纳米管（SWNTs）在水中作为“去缠结”，同时保持其独特的物理性质是非常有用的。我们在这里提出了一系列的阳离子胆固醇化合物（Chol+）{胆甾-5烯-3β-氧基乙基吡啶溴化物（Chol-PB+），胆甾-5烯-3β-氧基乙基 N-甲基吡咯烷溴化物（Chol-MPB+），胆甾-5烯-3β-氧基乙基 N-甲基吗啉溴化物（Chol-MMB+）和胆甾-5烯-3β-氧基乙基二氮杂二环辛烷溴化物（Chol-DOB+）}。这些化合物都可以很容易地分散在水中。所得的阳离子胆固醇（Chol+）悬浮液通过 Chol+对单壁碳纳米管（SWCNTs）的非特异性物理吸附来溶解单壁碳纳米管（SWCNTs），在室温下形成稳定、透明、深色的水悬浮液。电子显微镜显示这些样品中存在高度分离的 CNTs。Zeta 电位测量表明，随着 CNTs 的加入，阳离子胆固醇聚集体的电位增加。CNT-Chol+悬浮液能够与基因（DNA）有效地形成稳定的复合物。在加入阴离子胶束溶液 SDS 后，这种 CNT-Chol+复合物中的双链 DNA 可以从复合物中释放出来。此外，含有阳离子胆固醇聚集体的基于 CNT 的 DNA 复合物在生理条件下的胎牛血清介质中表现出更高的稳定性。共聚焦研究证实，CNT-Chol+配方黏附在 HeLa 细胞表面，并比单独的阳离子胆固醇悬浮液（不含任何 CNTs）更有效地被内化。因此，这些阳离子胆固醇-CNT 悬浮液似乎是进一步在生物应用中使用的有前途的系统。
