A　label-free　and　enzyme-free　sensitive　fluorescent　detection　of　human　immunodeficiency　virus　(HIV)　deoxyribonucleic　acid　(DNA)　based　on　isothermal　hybridization　chain　reaction　(HCR)　was　developed.　A　G-quadruplex　sequence　which　was　incorporated　into　one　of　the　two　hairpin　probes　was　inactive　in　the　absence　of　target　DNA.　However,　at　the　presence　of　target　DNA　numerous　G-quadruplexes　along　DNA　nanowires　were　self-assembled　through　HCR.　Using　N-methyl　mesoporphyrin　IX　(NMM)　as　the　fluorophore,　a　＂turn-on＂　fluorescent　response　would　be　achieved　and　detected　as　low　as　0.5　nmol　L　(1)　of　HIV　DNA.　This　proposed　method　was　applied　to　detect　HIV　DNA　in　biologic　samples　with　satisfactory　results.　(C)　2014　Elsevier　B.V.　All　rights　reserved.