Enhanced sensitivity for biosensors: multiple functions of DNA-wrapped single-walled carbon nanotubes in self-doped polyaniline nanocomposites.

A nanocomposite of poly(anilineboronic acid), a self-doped polyaniline, with ss-DNA-wrapped single-walled carbon nanotubes (ss-DNA/SWNTs) was fabricated on a gold electrode by in situ electrochemical polymerization of 3-aminophenylboronic acid monomers in the presence of ssDNA/SWNTs. We used this nanocomposite to detect nanomolar concentrations of dopamine and found that the sensitivity increased 4 orders of magnitude compared to the detection at an electrode modified with only poly(anilineboronic acid). For the first time, this work reports the multiple functions of the ss-DNA/SWNTs in the fabrication and biosensor application of a self-doped polyaniline/ss-DNA/SWNT nanocomposite. First, the ss-DNA/SWNTs acted as effective molecular templates during polymerization of self-doped polyaniline so that not only was the polymerization speed increased but also the quality of the polymer was greatly improved. Second, they functioned as novel active stabilizers after the polymerization, significantly enhancing the stability of the film. Furthermore, the ss-DNA/SWNTs also acted as conductive polyanionic doping agents in the resulting polyaniline film, which showed enhanced conductivity and redox activity. Finally, the large surface area of carbon nanotubes greatly increased the density of the functional groups available for sensitive detection of the target analyte. We envision that polyaniline with other functional groups as well as other conducting polymers may be produced for different targeted applications by this approach.