Fabrication of single-walled carbon nanotubes dotted with Au nanocrystals: Potential DNA delivery nanocarriers

Single-walled carbon nanotubes (SWCNTs) dotted with Au nanocrystals (Au-SWCNTs) were fabricated by using a two-phase reduction of hydrogen tetrachloroaurate in the presence of thiol groups anchored to SWCNTs for their potential applications in DNA (deoxyribonucleic acid) delivery. To allow a surface reaction on SWCNTs during the metal nucleation and growth processes, Au nanocrystals were grown using a two-phase system. Raman, XPS and transmission electron microscopy results show that the Au nanocrystals were grafted primarily to the sidewalls of the SWCNTs. DNA probes were immobilized on Au-SWCNTs by the conjugation of DNA functionalized at the 3′ end with a thiol group with Au dots of SWCNTs, followed by hybridizion of complementary oligonucleotides, as verified by fluorescence-based measurements. To investigate whether the target DNA hybridized to DNA probes immobilized on Au-SWCNTs, 618-base-pair fragments of amplified DNA were prepared by polymerase chain reaction using plasmid pET-22b as a template. Atomic force micrograph (AFM) images show that the nanorod-bound DNA is recognizable with excellent specificity, indicating the potential use of such material as a versatile gene delivery carrier in gene-based disease therapy.