| "Electrochemical DNA analysis era had arrived." Which was commented by the the famous magazine-"Nature Biotechnology" in the year of 2000. Electrochemical detection method is considered as one of the first choices in terms of cost, time and other requirements of special occasion to construct biosensors, due to its fast response, high sensitivity, low-power requirement, portable device and easy to carry. Up to now, there is no doubt that molecular logic gates play an important role in the face of real-time, on-line analysis and simultaneous analysis of multiple targets, especially in the establishment of intelligent, automated analysis and detection systems. Construction of molecular logic gate is a prerequisite for the design of molecular computers, and using DNA molecules to build a DNA computer is one of human dreams. In this thesis, the DNA logic gates combined with electrochemical methods to achieve the detection of various foodborne pathogens features DNA simultaneously. The DNA logic gates were also preliminarily applied to construte a basic logic operation system （DNA half-adder）. These works paved a way for development of DNA computers in basic exploration field.The main research contents are as follows:（1） Construction of a NOR logic gate based on DNA induced to AgNCs for detection of multi-target DNAs simultaneously;Based on DNA-templated silver nanoclusters for multiplexed electrochemical DNA detection.We use Escherichia coli DNA and Salmonella DNA as inputs, silver ion electrochemical signal as outputs to construct a NOR logic gate, at the same time, it achieve the purpose of detection of Escherichia coli DNA and Salmonella DNA. The result of Sal DNA was obtained in the range from 5.0×10-8 mol·L-1 to 8.5×10-7 mol·L-1, the linear regression equation was Ip=-1.5×10-4（CSal/mol·L-1）+0.48（R=0.9956） with the detection limit of 3.3×10-8 mol·L-1. The result of E.coli DNA was obtained in the range from 5.0×10-8mol·L-1 to 8.5×10-7 mol·L-1, the linear regression equation was Ip=-1.4×10-4（CE.Coli/mol·L-1）+0.54 （R= 0.9932） with the detection limit of 2.1 x 10-8 mol·L-1.（2） Construction of ID B and OR logic gates based on GO/AuNPs （graphene oxide/gold nanoparticles） nanocomposites;This experiment use GO coated on glassy carbon electrode and AuNPs was then electrodeposited on the modified electrode, Preparation of GO/AuNPs composite film nanoelectrode ensembles. We use this GCE/GO/AuNPs as the working electrode, use Shigella DNA and Salmonella DNA as inputs, the current intensity of Fc as outputs to construct ID B and OR DNA molecular logic gates. The result of Sal DNA was obtained in the range from 1.0×10-12 mol·L-1 to 1.0×10-7 mol·L-1, the linear regression equation was Ip=-0.0241og （CSal/mol·L-1）+0.39（R= 0.9993） with the detection limit of 6.5×10-13 mol·L-1.These two logic gates have achieved the purpose of rapid detection of Shigella DNA and Salmonella DNA simultaneously.（3） Self-assembled DNA tetrahedron nanostructures probes to contruct NOR logic gate;The four autocorrelation complementary single strands of DNA was chosen in this experiment, it can form a rigid and stable tetrahedral DNA nanostructures, the DNA tetrahedron mechanical reconfiguration upon external chemical stimuli （target DNA）. We use Shigella DNA and Escherichia coli DNA as inputs, the current intensity of Fc as outputs to construct NOR logic gate to achieve detection of Shigella DNA and Escherichia coli DNA simultaneously. The result of Shi DNA was obtained in the range from 5.0×10-9 mol·L-1 to 7.5×10-7 mol·L-1 , the linear regression equation was Ip=-0.24log（Cshi/mol·L-1 ）+3.12（R=0.9928） with the detection limit of 2.1×10-9 mol·L-1 . The result of S E.coli DNA was obtained in the range from 3.0×10-10 mol·L-1 to 1.5×10-7 mol·L-1 , the linear regression equation was Ip=-0.281og（CE.coli/mol·L-1 ）+3.8（R=0.9978） with the detection limit of 6.1×10-11 mol·L-1 .（4） Construction of DNA half-adder and simultaneous detection of two pathogen DNAs;In this experiment, GO/AuNPs composite film modified glassy carbon electrode as the working electrode, DNA probes were labeled with two kinds of electrochemical activity indicators （Fc, MB）, in the same test system, simultaneous detection of two indicators signal change. We use Escherichia coli DNA and Salmonella DNA as inputs, △IMB+△IFc and |△IMB/△IFc| as different outputs to construct AND and XOR logic gates, and the combination of these two logic gates constructed a DNA half-adder. To amplify the electrochemical response, a linear dependence between the Σ|△I| and target DNA concentration. The result of E.coli DNA was obtained in the range from 1.0×10-13 mol·L-1 to 1.0×10-8 mol·L-1, the linear regression equation was （|△IFc|+|△IMB|）= 2.171og（CE.coli/mol·L-1）+32.03（R= 0.9931） with the detection limit of 3.2×10-14 mol·L-1. The result of Sal DNA was obtained in the range from 1.0×10-13 mol·L-1 to 3.0×10-8 mol·L-1, the linear regression equation was （|△IFc|+|△IMB|）= 2.491og（CSal/mol·L-1）+34.14 （R= 0.9967） with the detection limit of 1.7×10-14 mol·L-1. |
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