Traditional　organic　photoelectrochemical　transistor　(OPECT)　biosensing　offers　high　sensitivity　and　cost-effectiveness　for　bioanalytical　applications,　but　its　reliance　on　single-signal　output　limits　reliability　in　complex　biological　systems.　To　address　this　limitation,　a　novel　multimodal　biosensing　platform　was　developed　by　integrating　OPECT　with　smartphone　colorimetry　(SCL)　and　photothermal　imaging　(PTI)　for　gonyautoxin　1/4　(GTX　1/4)　detection.　The　system　employed　a　HOF-101@CdS　as　photoactive　material,　where　GTX　1/4　triggers　competitive　binding　that　releases　DNA　nanowires　and　CuO-DNA　probes　from　magnetic　bead　complexes.　Subsequent　acid　treatment　liberates　Cu2+　ions,　which　undergo　ion　exchange　with　HOF-101@CdS　to　form　photothermally　active　and　color-changed　CuS.　This　dual-response　mechanism　enables　three　complementary　detection　modes:　OPECT　measured　photocurrent　changes,　SCL　monitored　the　yellow-to-dark　color　transition　from　CdS　to　CuS,　and　PTI　quantified　heat　generation　from　CuS.　The　integrated　platform　achieves　exceptional　sensitivity　with　detection　limits　of　0.097　nM　(OPECT)　and　0.1　nM　(SCL),　while　maintaining　a　high　selectivity　against　interfering　substances.　The　photothermal　component　further　enabled　rapid　visual　assessment　using　portable　infrared　imaging.　Successful　application　in　real-sample　analysis　demonstrated　the　system＇s　practical　utility　for　marine　toxin　monitoring.　This　OPECT-SCL-photothermal　approach　overcomes　traditional　limitations　through　multi-signal　cross-validation,　significantly　enhancing　measurement　reliability　while　preserving　the　advantages　of　portability　and　operational　simplicity.　The　synergistic　combination　of　electronic,　optical,　and　thermal　detection　modalities　establishes　a　new　paradigm　for　field-deployable　biosensing　with　built-in　verification　capability,　particularly　valuable　for　environmental　monitoring　and　food　safety　applications.　©　2025　Elsevier　B.V.