MicroRNAs　can　serve　as　biomarkers　for　many　cancers,　so　it　is　significant　to　develop　simple　and　sensitive　strategies　for　microRNAs　detection.　Photoelectrochemical　(PEC)　detection　has　the　advantages　of　simple　equipment　and　high　sensitivity　But　in　conventional　PEC　DNA　sensors,　tedious　immobilization　procedures　of　photoactive　materials　and　capture　probes　on　electrode　surfaces　are　inevitable.　To　overcome　those　limitations,　a　homogeneous　PEC　biosensor　based　on　target-responsive　hydrogels　has　been　developed　(miRNA-155　has　been　chosen　as　a　model　target).　PEC　signal　molecules　(TiO2　nanoparticles,　TiO2　NPs)　were　embedded　in　DNA　hydrogels　formed　by　hyaluronic　acid　sodium　salt,　amine-modified　DNA　double　strands,　and　polyethylenimine　rich　in　amine　groups.　In　the　presence　of　the　target,　DNA　double　strands　in　hydrogel　were　nicked　by　endonuclease　and　TiO2　NPs　were　released　to　the　supernate　and　a　high　PEC　response　was　obtained　when　collecting　the　supernate　for　PEC　test,　while　almost　no　TiO2　NPs　released　in　the　absence　of　the　target.　Thanks　to　the　exonuclease　III　and　nicking　endonuclease　Nb.BbvCI-assisted　cascaded　amplification　strategy,　the　proposed　biosensor　exhibits　high　sensitivity　toward　miRNA-155　with　a　low　detection　limit　of　0.41　fM　and　a　wide　linear　range　from　1.0　fM　to　100　pM.　Since　this　method　circumvents　tedious　electrode　modification　procedures,　the　proposed　technique　exhibits　the　advantages　of　simplicity　and　good　reproducibility.　Moreover,　the　prepared　hydrogels　have　outstanding　storage　stability,　so　that　they　can　be　prepared　in　advance　and　shorten　detection　time.　This　biosensing　platform　provides　a　versatile　strategy　for　the　construction　of　homogeneous　PEC　biosensors　for　the　detection　of　diverse　targets.