Polymeric acid doped polyaniline nanotubes for oligonucleotide sensors

Template-free, self-assembled polyaniline (PANI) nanotubes were prepared in a solution of poly(methyl vinyl ether-alt-maleic acid) (PMVEA) by oxidative polymerization using ammonium persulfate as the oxidant. The weight ratio of the polymeric acid to aniline in the solution had a significant effect on the size of the polyaniline nanotubes as determined by SEM. The outer diameter of the nanotubes increased from 65 nm to 160 nm with increased levels of PMVEA in the reaction solution from 1 to 4 wt/v%. The PANI/PMVEA nanotubes were characterized by FTIR and cyclic voltammetry. The nanotubes were used to construct a simple electrochemical oligonucleotide (ODN) sensor where ODN probes were covalently grafted onto the residual carboxylic acid functionalities on the nanotubes. The potential pulse amperometry technique was used to obtain a direct and fast electrochemical readout.