| Streptomycin（STR）is a kind of antibiotic fungicide mainly used to control bacterial brown spot disease and bacterial rot disease.It has stable properties and long half-life,and it is also easy to be enriched in the environment,thus destroying the ecological balance and threatening human health.Therefore,achieving accurate detection of STR in the environment is of great significance to protect the ecological environment and human health.There are many methods for STR detection,but each method has its advantages and disadvantages.And it is necessary to develop detection platform that uses two or more methods to achieve accurate analysis of STR.This paper focuses on the construction of a dual-method based sensing platform and its application to the detection of STR in the environment.A ratiometric sensing strategy based on the combination of electrochemical and photoelectrochemical method is proposed to solve the problem of the dual response signal acquisition of STR and to improve the detection accuracy.Next,a triple-response signal sensing platform for STR was developed to achieve accurate STR analysis by introducing multi-role probe and combining with signal amplification technology.Finally,STR residues in the water environment of freshwater ecosystem in Zhenjiang area were investigated by using the proposed sensing platform.The work content of this paper mainly includes the following three parts:（1）A novel ratiometric sensing strategy by coupling electrochemical and photoelectrochemical method was proposed.The working principle is based on the STR-initiated aptamer conformation change to output electrochemical and photoelectrochemical signals.The quantitative analysis of STR was realized with the ratio of these two signals.The sensitive interfaces were constructed by using cadmium telluride quantum dots（CdTe QDs）and methylene blue-labeled aptamers（MB-Apt）as photoelectrochemical and electrochemical signal generators,respectively.For analysis,the formation of STR-MB-Apt complex led to its stripping from the eletrode,decresing the interfacial electron transfer resistance as well as the the MB content.In this way,the photoelectrochemical signal and electrochemical signal showed an increase and an decrease,respectively,and the detection of STR can be achieved by using the relationship between the ratiometric signal and the STR concentration.Under optimal conditions,the linear response range of the constructed aptasensor for STR analysis was 3.00×10-8-1.00×10-4 mol?L-1 with a detection limit of1.00×10-8 mol?L-1.Besides,the sensor has been successfully applied to the detection of STR in actual water with a recovery rate between 96.9%and 103%.（2）To further improve the analytical performance of the sensor,the hybrid chain reaction was introduced to generate longer double strands DNA,while the positively charged MB as bifunctional probe was adsorbed by electrostatic adsorption to achieve simultaneous amplification of the electrochemical and photoelectrochemical signals.Using the electrochemical signal of ferrocene（Fc）and the electrochemical and photoelectrochemical signals of MB,a dual-ratiometric aptasensor for sensitive and accurate detection of STR in water was constructed.The sensor showed excellent signal amplification performance that the photoelectrochemical and electrochemical signals of MB increased by 4.12 and 4.78 times in the presence of 1.00×10-8 mol?L-1STR,respectively.The dual ratiometric sensor for STR ananysis provided a linear response range of 1.00×10-11-1.00×10-4 mol?L-1 with a detection limit of 3.33×10-12mol?L-1.The sensor was successfully used for STR analysis in water samples,and the resulting recovery was between 96.3%and 109%.（3）Based on the proposed dual ratiometric aptasensor,a systematic investigation was conducted on STR residue in the freshwater ecosystem water body in Zhenjiang area.18 representative water samples from Zhenjiang area were selected for blank test and standard addition test.The test results showed that no STR was detected in the water samples,and the results of the addition test demonstrated the accuracy of the sensor for STR detection.In this paper,a（dual）ratiometric sensing method based on the combination of electrochemical-photoelectrochemical method was proposed to improve the accuracy of streptomycin residue detection.It was successfully applied to evaluate streptomycin residues in freshwater ecosystem water in Zhenjiang urban area.The research work can provide technical support for the monitoring of streptomycin residues in water,and it has reference value for the development of novel ecological system of agricultural residue detection method. |
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