Wang Yixuan, Xu Zhenfeng
Computational Chemistry Laboratory, Department of Natural and Forensic Sciences, Albany State University, Albany, Georgia 31705, United States.
RSC Adv. 2016;6(1):314-322. doi: 10.1039/C5RA20866A. Epub 2015 Dec 3.
In the present work the adsorption of doxorubicin (DOX) on the surface of single-walled carbon nanotube (SWCNT) as well as its encapsulation in SWCNT, and their dependence on the protonation of NH group of DOX, solvent, and the diameter of armchair (n,n) SWCNT were systematically investigated using theoretical methods such as PM6-DH2 and M06-2X in the scheme of OMIOM. It was found that the two loadings, adsorption on the sidewall of CNT and the encapsulation in CNT, have distinct solvent, protonation and diameter dependences. The encapsulation is much stronger than the adsorption of DOX on the sidewall of CNT, and the former also has significantly higher solvent and protonation effects than the latter. The adsorption primarily occurs through π-π stacking and just becomes slightly stronger as the diameter of CNT increases, while besides π-π stacking the additional C-H/N-H/O-H…π and C=O…π also contribute to the encapsulation of DOX in CNT. It seems that (8,8) CNT (diameter ~ 11Å) energetically is an onset for the encapsulation since the encapsulation turns from endothermic to exothermic as the diameter is larger than approximately 11 Å, and the optimal diameter for the encapsulation is 14Å corresponding to (10,10) CNT. Thus for the thick CNT the encapsulation may also play an important role in the loading and releasing for the CNT-based drug delivery system of the DOX.
在本工作中，采用诸如OMIOM方案中的PM6-DH2和M06-2X等理论方法，系统研究了阿霉素（DOX）在单壁碳纳米管（SWCNT）表面的吸附及其在SWCNT中的包封情况，以及它们对DOX的NH基团质子化、溶剂和扶手椅型（n,n）SWCNT直径的依赖性。研究发现，两种负载方式，即吸附在碳纳米管侧壁上和包封在碳纳米管中，具有不同的溶剂、质子化和直径依赖性。包封作用比DOX在碳纳米管侧壁上的吸附要强得多，并且前者的溶剂和质子化效应也明显高于后者。吸附主要通过π-π堆积发生，并且随着碳纳米管直径的增加仅略微增强，而除了π-π堆积外，额外的C-H/N-H/O-H…π和C=O…π也有助于DOX在碳纳米管中的包封。似乎（8,8）碳纳米管（直径约11Å）在能量上是包封的起始点，因为当直径大于约11Å时，包封从吸热转变为放热，并且包封的最佳直径为14Å，对应于（10,10）碳纳米管。因此，对于较粗的碳纳米管，包封在基于碳纳米管的DOX药物递送系统的负载和释放中也可能起重要作用。
