IN THIS STUDY, WE DESCRIBE THE DEVELOPMENT OF TWO SIMPLE AND SENSITIVE ELECTROCHEMICAL ASSAYS FOR THE DETECTION OF APTAMER- MUC1 PROTEIN INTERACTIONS BASED ON SELF-ASSEMBLY OF THIOL-MODIFIED APTAMER PROBES ON GOLD ELECTRODE SURFACE. MUCLMUCIN IS AN INTEGRAL MEMBRANE GLYCOPROTEIN EXPRESSED BY MOST IF NOT ALL ‘WET’ EPITHELIA, SUCH AS ON BLADDER, BREAST, GASTRIC, PANCREAS AND OVARY [1]. IT PLAYS AN IMPORTANT ROLE IN THE TUMOR GENESIS OF SEVERAL CANCER TYPES. MUC1 OVER-EXPRESSION IS MOST EVIDENT, AND THESE RIGID MUCIN GLYCOPROTEINS ON CANCER CELLS PLAY A ROLE IN METASTASIS BY INHIBITING TUMOR CELL ADHESION AND IN ESCAPING FROM IMMUNE SURVEILLANCE. IT IS ALSO KNOWN THAT MUC1 ACTS AS DOCKING PROTEIN FOR SIGNALING MOLECULES [2].IN ORDER TO IMPROVE THE SENSITIVITY OF DESIGNED APTASENSOR, AU NANOPARTICLES WERE ELECTRODEPOSITED ONTO GOLD SCREEN PRINTED ELECTRODES (GSPES). THE QUANTITATIVE DETECTION OF MUC1 CANCER BIOMARKER WAS ACHIEVED BY ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) AND DIFFERENTIAL PULSE VOLTAMMETRY (DPV) TECHNIQUES. IMPEDANCE MEASUREMENTS WERE CARRIED OUT IN THE PRESENCE OF THE REDOX PROBE FERRI/FERRO CYANIDE THAT SHOWED AN INCREASE IN CHARGE TRANSFER RESISTANCE AFTER IMMOBILIZATION OF MUC1 PROTEINS TO THE SENSOR SURFACE. FOR DETECTION OF MUC1 BY DPV, THE ELECTROCHEMICAL RESPONSE OF METHYLENE BLUE (MB) WAS STUDIED IN THE PRESENCE OF DIFFERENT CONCENTRATIONS OF MUC1 PROTEIN. BINDING OF THE MUC1 PROTEIN TO THE APTAMER PREVENTS THE SUBSEQUENT INTERCALATION OF MB. THEREFORE, THE ELECTROCHEMICAL RESPONSE IS LESS THAN THAT OBSERVED IN THE ABSENCE OF PROTEIN. THE RESULTS DEMONSTRATE THAT THE ELECTROCHEMICAL METHOD USING APTAMER PROBE IS CONVENIENT, AND ALLOWS QUANTITATIVE DETECTION OF HUMAN MUC1 PROTEIN. THE CALIBRATION CURVE FOR THE DETERMINATION OF MUC1 PROTEIN WAS OBTAINED WITH BOTH TECHNIQUES UNDER OPTIMIZED CONDITIONS. THE ESTIMATED DETECTION LIMITS OF THE MUC1 CANCER BIOMARKER ARE 1.66 PPB AND 0.95 PPB BY EIS AND DPV METHODS, RESPECTIVELY.

IN THE LAKE OF GLUCOSE IN SOME BACTERIA, ARABINOSE BEGAN TO PRODUCE IN CELLULE. ARABINOSE IS A POISONOUS MATERIAL FOR HONEY BEE. SO DETECTION OF ARABINOSE IS IMPORTANT IN VETERINARY SCIENCE. IN THE PRESENT WORK, A NON-ENZYMATIC ARABINOSE BIOSENSOR USING A GOLD NANOPARTICLES ELECTRODE IS DESCRIBED. IN MODIFIED ELECTRODE, THIOLATED LIGAND, 1, 2, 4, 5-TETRAKISS [2-(4-PHENYL-5-THION-1, 2, 4- TREEAZOLE-3-ILE) PHENOXY METHYL]BENZENE (TPTAP) ACTS AS MEDIATOR TO IMMOBILIZE GOLD NANOPARTICLE TO THE SURFACE OF GOLD DISK ELECTRODE. THE VOLTAMMETRIC DETECTION OF ARABINOSE WAS PERFORMED BY AMPEROMETRY AND DIFFERENTIAL PULSE VOLTAMMETRY TECHNIQUES. THE AMPEROMETRIC AND DIFFERENTIAL PULSE VOLTAMMETRIC RESPONSES WERE LINEAR FROM 25 MM-0.3 MM AND 9 MM- 0.3 MM, RESPECTIVELY. THE PROPOSED BIOSENSOR CAN BE USED AS A SELECTIVE ARABINOSE DETECTOR IN THE PRESENCE OF URIC ACID AND ASCORBIC ACID. THE WIDE DYNAMIC RANGE AND HIGH SENSITIVITY, SELECTIVITY AND STABILITY, AS WELL AS GOOD BIOCOMPATIBILITY OF THE GOLD NANOPARTICLE MODIFIED ELECTRODE MAKE IT PROMISING FOR THE FABRICATION OF NON-ENZYMATIC ARABINOSE SENSORS.

GOLD NANOPARTICLES SIZE WHICH SYNTHESIS ON A SURFACE OR SUPPORT DEPENDS ON APPLICATION TYPE. IN THE GOLD NANOPARTICLES CATALYST FIELD, PARTICLES THAT ARE LESS THAN 10 NANOMETER IN SIZE IS NEEDED. CHOOSING APPROPRIATE PREPARATION METHOD TO CONTROL THE SIZE, SHAPE, AND CRYSTALLITE OF SYNTHESIZED PARTICLES DEPEND ON CATALYST SYSTEM TYPE (E.G., PRESENCE OF OXIDE SUPPORT OR IN POROUS MATRIX AND DENDRIMER) IS VERY IMPORTANT. WHILE FOR PHYSICAL OR BIO-APPLICATIONS LARGER PARTICLES CAN BE USED. SYNTHESIZING OF CATALYSTS IS DONE BY CHEMICAL METHODS [1, 2]. ALSO, GOLD NANOPARTICLES CAN BE SYNTHESIZED ON AN ORGANIC SUPPORT OR INTO AN ORGANIC COMPOUND LIKE DENDRIMERS. IN GENERAL, THE RELEVANT CHEMICAL METHODS CONSIST OF REDUCTION-PRECIPITATION AND PRECIPITATION-REDUCTION WAYS. AT FIRST, INITIALLY GOLD PRECURSOR (USUALLY HYDROGEN TETRACHLOROAURATE (III)) REDUCED AND THEN PRECIPITATED ON SUBSTRATES SUCH AS INORGANIC POWDERS OR INTO POROUS MATERIALS. REVERSELY, IN THE SECOND METHOD, INITIALLY GOLD PRECURSOR INTO OR ON DESIRED SUBSTRATES PRECIPITATED AND THEN THE REDUCTION IS DONE [2-6]. IN THIS STUDY, VARIOUS SYNTHESIS METHODS OF GOLD NANOPARTICLES FOR CATALYST APPLICATIONS ARE DISCUSSED IN DETAILS.