Abstract:A new biosensor platform was explored for detection of surfactant based on ?uorescence changes from single strand DNA (ssDNA) and single-walled carbon nanotubes (SWNTs). Thermodynamics assay was performed to value the stability of probe. The affinities of SWNT to five common surfactants (SDS, DBS, Triton X-100, Tween-20 and Tween-80) were investigated by real-time fluorescence method. The effects of Mg²⁺ and pH on the fluorescence intensity of self-assembled quenched sensor were performed. The fluorescent emission spectra were used to measure the responses of self-assembled quenched ?uorescent of ssDNA /SWNTs to different concentration surfactant(Triton X-100). The FAM-DNA wrapped SWNTs probe was stable in a wide temperature range   (5 °C to 80 °C). The binding strength of surfactants and single-stranded DNA (ssDNA) on SWNTs surfaces was shown as follows: Triton X-100>DBS>Tween-20>Tween-80>ssDNA>SDS, and the optimized reaction conditions included pH 7.4 and 10 mmol/L Mg²⁺. The fluorescence of FAM-ssDNA wrapped SWNTs was proportionally recovered as a result of adding different concentrations of Triton X-100, which realizes the quantitative detection of Triton X-100.

Key words: single-stranded DNA; single-walled carbon nanotubes; surfactant; fluorescent sensor; affinity