We demonstrate that oxidized single-wall carbon nanohorns (SWNHs), a type of single-wall nanotube, entrap cisplatin, an anticancer agent. We found that the cisplatin structure was maintained inside the SWNHs and that the cisplatin was slowly released from the SWNHs in aqueous environments. The released cisplatin was effective in terminating the growth of human lung-cancer cells, while the SWNHs themselves had no such effect. Cisplatin-incorporated oxidized SWNHs are thus a potential drug delivery system.

We elucidated the secret of water-assisted chemical vapor deposition (CVD) by elucidating the influence of water on the catalysts, through ex situ microscopic and spectroscopic analysis. We unambiguously showed that catalyst deactivation readily occurs due to carbon coating and that water acted to remove this coating and revive catalysts activity. This represents the central point of water-assisted CVD.

Here we show that essentially any Fe compounds spanning Fe salts, nanoparticles, and buckyferrocene could serve as catalysts for single-walled carbon nanotube (SWNT) forest growth when supported on AlO(x) and annealed in hydrogen. This observation was explained by subsurface diffusion of Fe atoms into the AlO(x) support induced by hydrogen annealing where most of the deposited Fe left the surface and the remaining Fe atoms reconfigured into small nanoparticles suitable for SWNT growth. Interestingly, the average diameters of the SWNTs grown from all iron compounds studied were nearly identical (2.8-3.1 nm). We interpret that the offsetting effects of Ostwald ripening and subsurface diffusion resulted in the ability to grow SWNT forests with similar average diameters regardless of the initial Fe catalyst.

We incorporated cisplatin inside single-wall carbon nanohorns (NHs) and revealed that 70% of the cisplatin was released from NHs having holes with hydrogen-terminated edges when they were immersed in phosphate-buffered saline (PBS). However, only 15% was released from NHs having holes with oxygen-containing functional groups at the hole edges (NHox). Elemental analysis indicated that -COOH and -OH groups at the hole edges of NHox changed mainly to -COONa and -ONa groups by immersion in PBS. These groups decreased the practical hole diameters, which resulted in hindering the cisplatin release from NHox. This means that the release of the material from inside NHox would be controlled by chemically modifying the functional groups attached to the hole edges of NHox; thus the potential applicability of NHox to a material carrier would be enhanced.

Water-soluble carbon-nanohorn-tetrathiafulvalene (CNH-TTF) nanoensembles were prepared by utilizing positively charged pyrene as an assembly medium and characterized by spectroscopy and electron microscopy. Electronic interactions within the nanoensemble were probed by optical spectroscopy, indicating electron transfer between the TTF units and CNHs after light illumination.

Water‐soluble carbon nanohorns have been synthesized via the 1,3‐dipolar cycloaddition reaction of azomethine ylides (see figure). The introduction of fused substituted pyrrolidine rings onto the π‐skeleton of the nanohorns enhances solubility and generates materials potentially suitable for managing electron‐transfer processes.

We enclosed cisplatin (CDDP), an anticancer drug, inside single-wall carbon nanohorns (SWNH) with holes opened by being heated from room temperature to a target temperature (475-580 degrees C) in flowing dry air, with an increase rate of 1 degrees C/min. The optimum target temperature was found to be 500 degrees C, in terms of the least amount of CDDP deposited outside the SWNH, when the quantity of CDDP encapsulated inside the SWNH was 12 wt %. The incorporated CDDP was slowly released from the SWNH in phosphate buffer saline, and the released quantity was 80%, which was greatly improved from the previous value of 15%. This indicated that a CDDP-containing SWNH could become more potentially useful for biological applications.

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