Optical detection of DNA hybridization using absorption spectra of single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) exhibit sharp absorption peak distributions in the UV–vis–nIR range when they are individually dispersed in aqueous solution medium. In this paper, we developed SWCNT-based molecular probes by conjugating single-stranded DNA (ssDNA) with SWCNT. The DNA hybridization event was investigated using the absorption spectra of the ssDNA–SWCNT probes. The results showed that DNA hybridization on the sidewall of SWCNT resulted in systematic red shifts of the absorption spectra of semiconducting nanotubes. However, metallic species did not show any shift in the absorption spectra. The work demonstrated that ssDNA–SWCNTs probes might be used to detect specific kinds of DNA oligonucleotides as optical nano-biosensors.