Novel Aptamer-based Electrochemical Sensors For Cocaine And ATP Detection

An efficient,highly sensitive and highly selective detection method is essential in the field of food quality and safety detection.The advantages of electrochemical sensor of nucleic acid aptamer include fast detection speed,low detection cost,simple detection operation,high specificity and high selectivity of detection results.Therefore,the application of nucleic acid aptamer electrochemical sensor in the field of food quality and safety analysis can greatly improve the detection speed of food.At present,most of the research work on the electrochemical sensor of nucleic acid aptamer focuses on the optimization of the sensitivity,but lacks the improvement of the sensor's working efficiency.In order to better solve the problems of slow detection speed and low sensitivity of the electrochemical sensor of nucleic acid aptamer,the following two parts are studied.The first part is"electrochemical sensor of cocaine aptamer based on one-step competitive binding",and the second part is"electrochemical sensor of ATP based on synergistic stable double-stranded aptamer probe".Both of these methods build a more rapid and sensitive aptamer sensor detection platform.The main research contents and results of this paper are as follows:(1)Design and application of electrochemical sensors based on one-step competitive binding of nucleic acid aptamers.In this paper,the detection performance of cocaine by conventional permutation type electrochemical sensor and one-step competitive type electrochemical sensor was compared in detail.The results show that one-step competitive nucleic acid fitness electrochemical sensor is superior to the conventional replacement nucleic acid fitness electrochemical sensor in detecting speed and signal gain.Then the electrochemical sensor of a competitive cocaine nucleic acid adaptor was designed,and the effects of the length of the complementary chain,the concentration of the complementary chain and the fixed concentration of the nucleic acid adaptor chain on the signal gain of the sensor were investigated.The detection performance of the sensor under optimal experimental conditions:the response time of the sensor to the target molecule Cocaine was 15 minutes,and the linear equation of the sensor for the quantitative analysis of Cocaine was SI/%=1.39939×[Cocaine]?M+12.11468(R~2=0.99375),with a linear range of0.5~100×200?M(200 times).The standard recovery rate of the actual samples is as high as 94%.The experimental results are sufficient to show that the one-step electrochemical sensor design is effective and can effectively improve the sensitivity and response speed of the sensor,and the practical application in the detection of cocaine in samples has a high accuracy.(2)Design and application of electrochemical sensors for synergistically stabilized double-stranded nucleic acid aptamers.Firstly,this paper explores whether the length and position of the complementary chain have an effect on the detection performance of the synergistically stable double-stranded aptamer electrochemical sensor.Research results show that when complementary strand is"5+X"(5 said the aptamer base sequence,X represents a base number of the complements aptamer structure,nucleic acid adaptation of body and the combination of the space steric hindrance between ATP will greatly reduced,thus can target molecules ATP faster solve double chain structure and complete the substitution reaction,response speed of the electrochemical sensor can also promote quickly.When the complementary chain length(5+7,5+6,5+5 base pairs)is reduced,the background suppression of the sensor interface will also be reduced in turn.Finally,when the complementary length is"5+6"base pairs,the response value of the electrochemical sensor with the synergistically stable double-stranded nucleic acid aptamer is determined to be the best.Then the effects of the complementary chain concentration,the concentration of salt ions in the buffer solution and the square wave voltammetry frequency on the signal gain of the sensor are optimized.The experimental results show that the detection performance of the sensor under the optimal experimental conditions is:the response speed to the target molecule ATP is 1 minute,the linear equation for the quantitative analysis of ATP is SI/%=1.5041×[ATP]/?M+19.02(R~2=0.9986),and the linear range is 0.5~100?M(200 times).The sensor can specifically identify the target molecule ATP in the complex mixture,and the recoveries measured in the actual samples are up to over 97%.The experimental results are sufficient to show that the design scheme of the double-chain ATP nucleic acid adaptor electrochemical sensor can greatly improve the sensitivity and response speed of the adaptor sensor,and the practical application of ATP detection in samples also has a high accuracy.