Non-invasive　early　diagnosis　of　HIV　is　an　important　and　effective　means　to　reduce　death　from　this　disease.　In　this　manuscript,　we　describe　a　method　using　a　novel　label-free　electrochemical　DNA　biosensor　for　HIV　related　gene　diagnosis　with　ultrahigh　sensitivity　and　selectivity.　The　DNA　biosensor　was　based　on　the　interaction　of　hybrid　double-stranded　DNA　and　protein.　In　the　presence　of　target　DNA,　the　target/probe　hybridization　encountered　the　NF-kB　protein.　Upon　addition　of　HRP,　they　formed　the　sandwich-like　DNA　sensor.　The　formed　sandwich-like　ds/NF-kappa　B/HRP　complex　effectively　catalyzed　the　H2O2-mediated　oxidation　of　TMB,　accompanied　by　a　changed　color　of　the　reaction　solution　and　an　increased　electrochemical　current　signal.　However,　in　the　absence　of　target　DNA,　no　duplex　DNA　could　bind　NF-kB　protein　or　HRP　to　form　the　DNA　sensor.　By　employing　the　above　strategy,　the　DNA　biosensor　was　able　to　gain　an　amplified　electrochemical　signal　and　thus　detected　as　low　as　7.05　pM　target　DNA.　Due　to　the　high　selectivity　of　the　method,　the　developed　biosensor　also　exhibited　high　discrimination　ability　even　against　single-base　mismatch.　Combined　with　the　advantages　of　electrochemical　detection　and　its　ready　integration　with　microelectronics,　the　proposed　electrochemical　DNA　biosensor　might　represent　a　promising　path　toward　direct　HIV　detection　at　the　point　of　care.　(C)　2013　Elsevier　B.V.　All　rights　reserved.