Carbon nanotubes (CNTs) are composed of two-dimensional hexagonal graphite sheets rolled up to form into a seamless hollow tube or cylinder of diameters ranging from 0.7 to 100 nm and length of several micrometres up to several millimetres [1, 2]. CNTs can be synthesised in two configurations, as single-walled nanotubes (SWCNTs) and multi-walled nanotubes (MWCNTs). Whereas SWCNTs are made of one tubular structure, MWCNTs consist of concentrically arranged carbon tubes with a typical spacing of ≈ 0.34 nm between the different layers. Owing to their remarkable structural characteristics (light weight, high aspect ratio, high specific surface area), as well as attractive mechanical (high stiffness and strength), electrical (high conductivity) and chemical (versatile surface chemistry, easily to functionalise) properties [2], there is increasing interest in biomedical applications of CNTs.
