A　simple　and　low-cost　electrochemical　immunosensing　platform　with　a　personal　glucometer　(PGM)-based　signal　readout　device　was　developed　for　the　quantitative　detection　of　human　carbohydrate　antigen　125　(CA　125)　using　invertase　for　the　hydrolysis　of　sucrose.　To　achieve　a　high　sensitivity,　branched　platinum　nanowires　(BPtNWs)　synthesized　by　a　wet-chemistry　method　were　utilized　for　the　conjugation　of　invertase　and　anti-CA　125　secondary　antibody.　The　immuno-reaction　was　carried　out　on　an　anti-CA　125　capture　antibody-coated　polystyrene　microtiter　plate　with　a　sandwich-type　assay　mode,　using　the　biofunctionalized　BPtNWs　as　signal-generation　tags.　Accompanying　the　formation　of　the　sandwiched　immuno　complexes,　the　carried　invertase　with　the　BPtNWs　hydrolyzed　sucrose　into　glucose　and　fructose.　The　glucose　produced　could　be　determined　for　quantification　using　a　portable　personal　glucometer.　By　integrating　the　secondary　antibody　and　invertase　with　branched　platinum　nanowires,　this　method　displayed　an　excellent　sensitivity　with　a　detection　limit　of　23　mU　mL-1　CA　125.　The　selective　experiments　revealed　that　the　developed　system　was　specific　for　the　target　CA　125,　even　coexisting　with　a　high　concentration　of　other　biomarkers.　Finally,　analysis　of　human　serum　samples　was　also　performed,　showing　that　our　strategy　was　reliable　and　had　great　potential　application　in　early　clinical　diagnostics.　©　The　Royal　Society　of　Chemistry　2016.