VITAMIN K3 (MENADIONE, 2-METHYL-1, 4-NAPHTHOQUINONE) IS A SYNTHETIC DERIVATIVE OF VITAMIN K1, WHICH EXHIBITS ANTITUMOR ACTIVITY AGAINST LIVER, CERVIX, NASOPHARYNX, COLON, LUNG, STOMACH, BREAST, LEUKEMIA AND LYMPHOMA CELL LINES [1]. THE MOLECULAR MECHANISMS OF MENADIONE CYTOTOXICITY ARE COMPRISED OF TWO MAIN COMPONENTS: A) COVALENT BINDING TO MACROMOLECULES (PROTEIN, DNA) VIA MICHAEL ADDITION B) FORMATION OF ROS THROUGH REDOX CYCLING, RESULTING IN OXIDATIVE STRESS THAT CAN OXIDIZE LIPID, PROTEIN AND DNA.VITAMIN K3 IS REDUCED INTRACELLULARLY VIA ONE OR TWO-ELECTRON TRANSFER. THE TWO ELECTRON REDUCTION OF QUINONE TO HYDROQUINONE CAN FORM NONTOXIC CONJUGATES OR SLOWLY AUTOXIDIZE TO REFORM QUINONE. AFTER THE SINGLE-ELECTRON REDUCTION OF THE QUINONE TO SEMIQUINONE, THE SEMIQUINONE REDUCES OXYGEN TO THE SUPEROXIDE RADICAL AND REGENERATES THE QUINONE. AS A RESULT, REDOX CYCLING CAN ENSUE AND PRODUCE LARGE AMOUNTS OF SUPEROXIDE, WHICH CAN DISMUTATE VIA SUPEROXIDE DISMUTASE TO FORM H2O2 AND O2 OR TAKE PART IN METAL-CATALYZED REACTIONS TO FORM MORE TOXIC SPECIES OF ACTIVE OXYGEN [2].A BIOSENSOR BASED ON INTERACTION OF MENADIONE AND DAMAGE OF H2O2 AND OTHER ROS AT A SALMON SPERM DS-DNA–MODIFIED PENCIL GRAPHITE ELECTRODE AND PDDA-MWCNTS (DNAPDDA MWCNTS–PGE) WAS INTRODUCED AS A PROMISING TOOL FOR SURVEY BEHAVIOR OF MENADIONE. THE MECHANISM OF THE INTERACTION AND DAMAGE WAS INVESTIGATED AND CONFIRMED BY DIFFERENTIAL PULSE VOLTAMMETRY (DPV) AND ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS).THE CHANGES IN THE CURRENT OF THE OXIDATION SIGNALS OF GUANINE AND ADENINE WERE OBTAINED BEFORE AND AFTER INTERACTION AND DAMAGE WITH MENADIONE.THE DAMAGE OF DSDNA BY DAMAGING REAGENTS DECREASES THE CHARGE TRANSFER RATE BY REDUCING THE NEGATIVE CHARGE ON THE ELECTRODE SURFACE.