A　versatile,　ultrasensitive　immunosensor　for　detection　of　influenza　virus　was　designed　by　combining　silver　nanoparticles　(Ag　NPs)　labeled　antibodies　with　indirect　fluorescence.　A　new　technology　using　Ag-S　covalent　binding　was　applied　for　antibody　labeling.　Influenza　A　(H1N1)　virus,　as　a　subtype　of　influenza　A　virus　that　was　the　most　common　cause　of　human　influenza　(flu),　was　acted　as　the　target　antigen　using　sandwich　type-immunoreactions　on　the　high　binding　ELISA　plates.　The　antibody-labeled　Ag　NPs　were　then　released　by　acid　solution　to　produce　Ag+　which　can　catalyze　o-phenylenediamine　(OPDA)　oxidation　to　produce　fluorescence　for　highly　sensitive　detection.　Under　the　optimal　conditions,　it　shows　good　linear　relationship　between　fluorescence　intensity　and　the　logarithm　of　the　concentration　of　H1N1　over　the　range　of　1.0　x　10(-12)-1.0　x　10(-8)　g　mL(-1)　with　a　detection　limit　(LOD,　3　sigma)　of　1.0　x　10(-13)　g　mL(-1).　Results　indicated　that　the　proposed　method　give　a　good　sensitivity　and　simple　operation　for　detecting　the　influenza　virus.　This　work　also　provided　a　promising　potential　for　antigen　detection　by　Ag　NPs　labeled,　and　the　steps　were　easy　to　handle.　(C)　2013　Elsevier　B.V.　All　rights　reserved.