Polyaniline (PANi) films with high conductivity and nanostructure were prepared by a modified dipping method using four acids on a polytetrafluoroethylene (PTFE) substrate. The "doping-dedopingre-doping'' process was carried out to investigate whether the electrical and surface properties of PANi coating could be changed. We found that the conductivity decreased with prolonged immersing time in both water and DMEM, until the PANi films were almost non-conductive. The as-prepared PANi films were hydrophilic, and the immersing treatment with DMEM made them hydrophobic. Moreover, they recovered their hydrophilicity following the redoping treatment. The morphologies of the PANi films became heterogeneous after the immersing-redoping treatment. These results provide a good reference for the use of conducting polymers as a neural probe coating. (c) 2008 Elsevier B.V. All rights reserved.