Preparation of biocompatible multi‐walled carbon nanotubes as potential tracers for sentinel lymph nodes

Carbon nanotubes (CNTs) are capable of traversing cellular membranes by endocytosis and are therefore promising materials for use in imaging and drug delivery. Unfortunately, pristine CNTs are practically insoluble and tend to accumulate inside cells, organs and tissues. To overcome the poor dispersibility and toxicity of pristine CNTs, hydrophilic functionalization of CNTs has been intensively investigated. Water‐soluble multi‐walled carbon nanotubes (MWCNTs) were prepared by in situ polymerization of acrylic acid in a poor solvent for poly(acrylic acid) (PAA). The solvent type influenced the grafted density and chain length of PAA. MWCNTs with a high grafted density of PAA (22 wt%) could be well dispersed in water, NaCl aqueous solution (0.9 wt%) and cell culture media. The in vitro cytotoxicity of these MWCNTs for endothelial cells is reasonably low even at high concentration of PAA‐g‐MWCNT (70 µg mL^?1). The experimental results show that the biocompatibility of these MWCNTs is sufficient for biological applications. PAA‐g‐MWCNTs were successfully utilized for lymph node tracing. Experimental results suggest that PAA‐g‐MWCNTs have potential to be used as a vital staining dye, which may simplify the identification of lymph nodes during surgery. Copyright © 2009 Society of Chemical Industry