ABSTRACT
Functionalization .............................................................................. 174 5.5 Toxicity ......................................................................................................... 176
5.5.1 Noncytotoxic CNT Bioconjugates .................................................... 179 5.6 Cell Imaging ................................................................................................. 183
5.6.1 Cell Imaging Using Intrinsic NIR Fluorescence of CNTs ............... 183 5.6.2 Cell Imaging by FITC Fluorescent Probe on CNTs ......................... 184 5.6.3 Cell Imaging by Cyanine Dye as Probe on CNTs ............................ 185 5.6.4 Photoacoustic Imaging ..................................................................... 186 5.6.5 Mechanism of CNT Internalization ................................................. 186
5.7 Pharmacokinetics ......................................................................................... 187
The carbon nanotubes (CNTs) categorized as multiwalled CNTs (MWNTs)1-3 and single-walled CNTs (SWNTs)4,5 exhibit unique mechanical, structural, and electrical properties. They have a high aspect ratio, lengths from several hundred nanometers to several micrometers, and diameters of 0.4-2 nm for SWNTs and 2-100 nm for coaxial MWNTs. These one-dimensional carbon allotropes are the ultimate carbon fibers. They are ultra lightweight, have the highest mechanical strength of all known materials, highest thermal conductivity, outstanding field emission properties, and can function as the active semiconductors in nanoscale devices. Metallic CNTs conduct electricity without dissipating heat. The nanotubes can absorb gas molecules as nano capillaries, be dissolved in surfactants, and undergo chemical derivatization for a myriad of additional functions. The last two decades have witnessed tremendous academic interest in CNTs, due largely to their attractive properties and potential applications in diverse fields, resulting in an avalanche of literature, summarized in several state-of-the-art reviews,6-11 books, and monographs.12-27 Initial interest in application of CNTs stemmed from their exceptionally high tensile strength and stiffness,leading to CNT-based advanced composite materials,28 while in recent times their unique geometry offers promising applications in biology and medicine.29-36 In this chapter, syntheses of some CNT bioconjugates and their biological and biomedical applications are discussed with a brief introduction on the structure and reactivity of the nanotubes.
