Novel Aptamer-based Electrochemical Sensors For Cocaine And ATP

Fast,simple and highly sensitive detection methods play a key role in ensuring food quality and safety,and this is an important research topic in the field of food quality and safety detection.Aptamer electrochemical sensor is a kind of detection tool that uses aptamer as the recognition element to quantify target molecules through electrical signals.Because of its simple design,fast speed,and good specificity,it has a wide range of application potential in food quality and safety testing.In this thesis,small molecules of Cocaine and Adenosine triphosphate are used as the detection objects to study and design aptamer probes with rapid recognition and high-sensitivity signal response to target molecules.Based on this,the electrochemistry for the detection of two target molecules is constructed.The main research content and conclusions of the thesis are as follows.The first part adopted the idea of"base truncation"and designed three hairpin type cocaine aptamer probes H1,H2 and H3 with different base lengths.The H1 chain is a recognition probe containing 38 original aptamer bases and a spacer base t,the H2 chain contains 30 aptamer bases and a spacer base t,and the H3 chain contains 28 aptamer bases and a spacer base.Through CV characterization and SWV scanning,the response signals of the three probes to the target molecule were compared,and the H2 aptamer strand with the highest signal sensitivity was screened out as the recognition probe and the electrochemical sensor was constructed.According to the SWV detection signal gain,the experiment determined that the optimal detection conditions of the sensor were:frequency 50 Hz,Na Cl addition concentration 50 m M,H2 probe fixed concentration 100n M,and detection stabilization time 5 min.Under optimized experimental conditions,the linear range of the aptamer electrochemical sensor based on H2 aptamer modified electrode for cocaine detection is 10～800μM,and the linear equation is SI/%=0.105×[cocaine]/μM+13.12,R~2=0.9903.This type of sensor has high specificity and good selectivity,and has a high recovery rate for the detection of cocaine in actual samples.The idea of adjusting the signal sensitivity of the aptamer electrochemical sensor by changing the length of the aptamer base sequence proposed in this experiment has a certain reference effect for the further development of simple and highly sensitive aptamer electrochemical sensor.In the second part,a new idea was proposed to significantly enhance the signal sensitivity of the nucleic acid aptamer electrochemical sensor through the"solution generation-electrode collection"working mode,and based on this,a new method for the target molecule Adenosine tricarboxylate was developed.In this sensor,a short signal nucleic acid probe labeled with methylene blue(MB)on the end of the electrical signal molecule hybridizes with the aptamer strand of ATP to form a double-stranded nucleic acid aptamer probe through base complementary pairing.The target molecule ATP binds to the aptamer in the double-stranded nucleic acid aptamer probe in the test solution to replace the signal nucleic acid probe to generate a free signal nucleic acid probe in the solution.Then the electrode is modified by the capture nucleic acid probe to collect and generate the electric current signal of the electric signal molecule MB on the electrode surface.The"solution generation-electrode collection"working mode is formed.Compared with the traditional electrochemical sensor based on double-stranded nucleic acid aptamer probe modified electrode,the sensitivity of this type of sensor is increased by nearly 5 times.By optimizing the collection time of the modified electrode for the signal nucleic acid probe,the concentration of the double-stranded nucleic acid aptamer probe in the test solution,and the fixation density of the capture nucleic acid probe on the surface of the modified electrode,the detection performance of the sensor for the target molecule ATP is obtained as follows:The linear range is 1.0～400μM,the linear equation is SI/%=1.5187×[ATP]/μM+0.0366,R~2=0.9955;the sensor has good specificity and selectivity for the detection of target molecules,and is used in human urine In the detection of spiked ATP,the recovery rate is good.