Label-free electrochemical immunosensor for detection of oncomarker CA125 in serum

•A new biosensor to ovarium cancer was developed using modified screen-printed carbon electrode.•The immunosensor was able of detect until 1.45 U mL−1 of oncomarker CA125.•The immunosensor was successfully applied in biological sample using DPV, SPR and AFM.•The immunosensor was able of discriminate negative and positive serum.