A new type of biocomposites – the polyaniline - deoxynucleic acid (PAN / DNA) and the poly-(o-phenylenediamine)-DNA (POPD-DNA) complexes can be synthesized electrochemically in acidic media in the potential range of –0.2V to 0.8 V vs. Ag/AgCl reference electrode, respectively. The ultraviolet-visible (UV-Vis) spectroscopy, the alternating-current impedance, the electrochemical quartz crystal microbalance (EQCM) and the voltammetry techniques have been used to characterize the above system. Results revealed that during the surface composite formation, DNA is incorporated into the polyaniline and the poly-o-phenylenediamine) networks, respectively. DNA also serves as a template to guide the surface synthesis of the oxidative polymerization. It provides a lower local pH environment that favors the protonation of aniline monomers, and subsequently minimizes the branching of the polymer network.