Substituted Carborane-Appended Water-Soluble Single-Wall Carbon Nanotubes: New Approach to Boron Neutron Capture Therapy Drug Delivery

Abstract

Substituted C₂B₁₀ carborane cages have been successfully attached to the side walls of single-wall carbon nanotubes (SWCNTs) via nitrene cycloaddition. The decapitations of these C₂B₁₀ carborane cages, with the appended SWCNTs intact, were accomplished by the reaction with sodium hydroxide in refluxing ethanol. During base reflux, the three-membered ring formed by the nitrene and SWCNT was opened to produce water-soluble SWCNTs in which the side walls are functionalized by both substituted nido-C₂B₉ carborane units and ethoxide moieties. All new compounds are characterized by EA, SEM, TEM, UV, NMR, and IR spectra and chemical analyses. Selected tissue distribution studies on one of these nanotubes, {([Na⁺][1-Me-2-((CH₂)₄NH-)-1,2-C₂B₉H₁₀][OEt])_n(SWCNT)} (Va), show that the boron atoms are concentrated more in tumors cells than in blood and other organs, making it an attractive nanovehicle for the delivery of boron to tumor cells for an effective boron neutron capture therapy in the treatment of cancer.