Water-Dispersible and Magnet-Responsible Carbon Nano Test Tubes with Controlled Size

Uniform carbon nano test tubes including magnetic metal particles inside their one-dimensional cavities were synthesized by the template method. The "as synthesized" metal-filled test tubes (35 nm in diameter and 1400 nm in length) were dispersible in ethanol, but not in water. To improve the water-dispersibility of the test tubes, their surface was treated with hydrogen peroxide and, as a result, they became water-dispersible and kept the dispersion state for several months. The tubes dispersed in water are responsive to an external magnetic field. If drugs, proteins or other biomacromolecules are incorporated into the cavities of such metal-filled test tubes, they would be useful for the delivery of biomacromolecules to a target tissue by a magnetic field. Introduction Nanocarbon materials are one of the possible candidates as a carrier for drug and gene delivery system (Pantarotto et al.), since carbon has less toxicity and its surface modification is very easy. The delivery by using a magnet has been proposed (Häfeli et al.) as one of the delivery methods. In this technique, a carrier conjugated with a magnetic material is leaded to a target tissue by an external magnetic field. However, nanocarbons useful for such applications have rarely been reported except for a few studies (Utsumi et al.). Very Recently, we have succeeded in the synthesis of carbon nano test tubes with tunable size both in diameter (10 nm~) and length (~10 μm) by using nanochannels of an anodic aluminum oxide (AAO) film as a template (Orikasa et al.). Since the tubes are water-dispersible and one of their ends is always open, they can be used as a capsule for the delivery system. In the present study, with the future application to the magnetic drug delivery system in mind, we attempted to introduce a magnetic material into the nano test tubes and to synthesize water-dispersible and magneto-responsive carbon tubes.