Research　has　shown　that　the　expression　level　of　microRNA-155　(miRNA-155)　is　positively　correlated　with　clinical　stage　and　depth　of　invasion　in　patients　with　cervical　cancer　and　cervical　intraepithelial　neoplasia　and　tends　to　be　highly　expressed.　Therefore,　it　is　very　important　to　develop　sensitive　miRNA-155　analysis　methods　for　the　early　diagnosis,　treatment,　and　prognostic　evaluation　of　cervical　cancer.　In　this　study,　a　near-infrared　light-driven　fluorescent　biosensor　based　on　the　metal-enhanced　fluorescence　effect　of　polydopamine-coated　upconversion　nanoparticle　(UP/Au)　and　two　toehold-mediated　strand　displacement　(TMSD)　steps　was　constructed　for　the　detection　of　miRNA-155.　The　target　miRNA-155　can　undergo　a　TMSD1　reaction　with　single-stranded　DNA1　(ssDNA1)　modified　on　wrinkled　silica　(WSNs)　to　form　the　ssDNA1/miRNA-155　complex　and　expose　toehold　2.　Through　the　TMSD2　reaction,　ssDNA2　adsorbed　on　the　UP/Au　surface　reacts　with　ssDNA1　to　form　the　ssDNA1/ssDNA2　complex,　which　replaces　miRNA-155　and　enables　the　recovery　of　the　UP/Au　fluorescence　signal.　The　target　miRNA-155　was　reacted　with　the　new　ssDNA1　to　amplify　the　detection　signal,　with　a　detection　range　of　0.5-20　pM　and　a　detection　limit　of　19.76　fM　for　miRNA-155.　In　addition,　the　fluorescent　biosensor　has　been　applied　for　the　analysis　of　miRNA-155　in　serum　samples,　indicating　its　good　practicality.　©　2024　The　Royal　Society　of　Chemistry.