| The incidence of tumor diseases has been increasing year by year,which is difficult to cure and seriously jeopardize human physical and mental health.The therapeutic regimen for early tumors haven’t to be developed yet.It is expected to develop the most powerful method for early diagnosis through accurate and rapid detection of markers（tumor markers）,closely related to the expression of cancer cells.With the advances in metal nanomaterials（MNMs）research,it has been found that MNMs have their unique advantages as mediators carrying biomolecules.MNMs are consummate carriers,due to their unique properties,such as good biocompatibility,high electrical conductivity,large surface area,and catalytic properties,and so on MNM,which enhances the analysis performance of sensor,has been used to construct various electrochemical sensors.It provides a new way for target detection by integrating with signal amplification technology,biomolecular specificity,and electrochemical biosensors.The combination of nanomaterial technology with a bipolar electrode electrochemical platform is expected to be build a portable detection platform.In this paper,two tumor markers,thrombin and microRNA,are measured in a closed bipolar electrochemical device.Our main work is as follows.1.Resistance-induced thrombin biosensorThe resistance of bipolar electrode has important influence on electrochemical signal.Firstly,we designed a closed bipolar electrochemical cell.By adding a standard resistor between the anode and cathode of the bipolar electrode,we studied the effect of the resistance on the redox reaction of the electroactive material at the bipolar electrode via cyclic voltammetry.When the resistance increases,the symmetry of the cyclic voltammetry curve does not change.However,the current was decreasing gradually and the absolute value of the peak voltage gradually increasing.A good linear relationship could be observed between peak voltages in forward and reverse scans and resistance between GCE BPE.In order to achieve sensitive electrochemical measurement,the scan rate and concentration of Fe（CN）63-/Fe（CN）64-were optimized.Then,a non-contact biosensor was designed to detect thrombin concentration.Biosensing interface was constructed on a splitted ITO electrodes.Chitosan was modified between the splitted electrode and aptamer was modified on its surface.By the following specific hybridization process,Au NPs labeled DNA could be captured on splitted ITO surface.After the exposure of it to silver enhancer solution,large amount of silver particles could be observed on ITO surface due to the catalytic effect of Au NPs.As a result,silver particles can form a electric bridge between the splitted ITO electrodes to form a continuous electrode.On the basis of the high affinity between thrombin and aptamer,the designed biosensor can achieve sensitive detection.The linear range was from 6×10-11 to 6×10-8M and the detection limit was 7.6×10-12M.2.Bipolar electrode electrochemical biosensor based on colorimetric methodBased on our previous research work,we know that the conductivity of the bipolar electrode has a great influence on the electrochemical signal on its surface.Therefore,we plan to electrodeposit prussian blue on one bipolar electrode and construct a biosensing interface for the detection of microRNA-182 at the anode of BPE.Through the oxidation of Ag at the anode of BPE,the prussian blue electrodeposition can be controlled.A method for detecting microRNA-182 was established based on the color change.We used carboxylated Fe3O4 beads as a substrate for the assembly of biomolecules.Silver nanoclusters synthesized by DNA-F template were bound to the electrode surface by DNA hybridization.Then,the oxidation of silver nanoclusters can control the prussian blue deposition at the other end of the bipolar electrode,realizing the visual detection of microRNA-182.In this paper,we realize a sensitive detection limit of 1.2×10-11 with a linear range of 5×10-10～1×10-6M. |
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