Glucose sensing based on NIR fluorescence of DNA-wrapped single-walled carbon nanotubes

DNA-wrapped individual single-walled carbon nanotubes (SWNTs) have been proposed for sensitive glucose detection based on the near-infrared fluorescence. A new approach for the immobilization of glucose oxidase (GOX) on SWNTs with keeping enzyme activity, which implies using of DNA as an interlayer between them, is suggested. The adsorption of the enzyme on DNA-wrapped nanotube has been demonstrated by the atomic force microscopy (AFM). GOX adsorbed on the nanotube frame retains its native globular structure. NIR luminescence properties of the aqueous solution of DNA-wrapped SWNTs do not change practically after GOX adding. The surface bound potassium ferricyanide (PFC) was used as an electron transfer mediator to improve the influence of the oxidizing properties of the enzyme on nanotubes emission. Quenched emission of the SWNTs after addition of PFC was easily restored by small glucose injections (1 mM) as a result of the reaction between PFC and H2O2 evolved during glucose oxidation. The increased nanotubes luminescence with rising glucose concentration in such small doses demonstrates the oxidizing activity of the enzyme after immobilization on the nanotube.