MicroRNAs　(miRNAs)　play　crucial　roles　in　the　regulation　of　immune　cell　differentiation　and　the　immune　response　during　allergic　rhinitis　(AR).　Studies　have　shown　that　miRNA-155　is　significantly　upregulated　in　AR　pathogenesis.　Therefore,　miRNA-155　can　be　used　as　a　biomarker　for　AR　diagnosis.　Although　fluorescent　biosensors　based　on　upconversion　nanoparticles　(UCNPs)　have　made　significant　advances　in　the　detection　of　miRNAs,　developing　UCNPs　with　polymer　coatings,　efficient　surface　passivation,　and　DNA　functionalization　for　hybrid　sensing　in　biological　media　remains　challenging.　Herein,　hairpin　DNA1　(H1)　is　modified　into　a　thin　polysulfonic　acid　layer　on　UCNPs　by　sulfonamide　bonds,　and　the　fluorescence　of　the　UCNPs　is　quenched　by　the　fluorescence　resonance　energy　transfer　(FRET)　process　of　BHQ3　carried　by　H1.　When　the　target　miRNA-155　is　present,　the　hairpin　structure　of　H1　is　opened,　allowing　BHQ3　to　move　away　from　the　UCNP　surface,　and　the　fluorescence　of　UCNP　is　restored.　At　the　same　time,　hairpin　DNA1　(H2)　can　combine　with　H1　to　replace　the　miRNA-155　that　is　bound　to　H1　with　the　help　of　the　opening　stem　ring　structure　of　H1,　and　the　replaced　miRNA-155　can　continue　to　react　with　H1　to　amplify　the　fluorescence　signal.　Under　the　optimal　experimental　conditions,　the　linear　range　of　miRNA-155　is　0.01-3　nM,　with　a　detection　limit　of　1.14　pM.　Furthermore,　the　constructed　biosensor　has　been　applied　to　determine　miRNA-155　in　serum　samples,　and　the　spiked　recoveries　range　from　99.8%　to　104.8%,　which　indicates　that　the　developed　assay　has　potential　applications　in　monitoring　allergic　rhinitis　or　other　miRNA　related　diseases.　©　2025　RSC.