| In the process of growth,development,reproduction and coping with different stresses,plants synthesize small molecules with certain biological activities in the body through their own metabolism,including related sugars,amino acids,plant hormones and various metabolites.Understanding the dynamic changes of the content of these small molecules in plants has an important influence on exploring the related physiological mechanisms of plants.Real-time and quantitative content of relevant small molecules in plants will provide relevant data support for crop yield assessment,quality identification and resistance judgment in the process of agricultural production,which is of great significance for the development of precision agriculture.Electrochemical sensing technology,as a new detection method,has been widely used in the field of detection of plant active small molecules.Compared with other traditional methods,it has the advantages of high efficiency,simplicity,portability and low cost.In this study,commercial screen printing electrodes were used as the base to construct two kinds of electrochemical biosensors for the detection of betaine and glucose respectively,which were used for actual samples and real-time in vivo detection.The conclusions are as follows:1.An electrochemical sensor based on molecular imprinting technology was successfully constructed for the detection of betaine.Dopamine as a functional monomer and betaine as a template were spontaneously polymerized on carboxylated multi-walled carbon nanotubes to form a molecularly imprinted polymer of polydopamine.A novel betaine sensor was constructed by modifying 0.1g /L gold nanoparticles on the screen printed electrode to improve the conductivity of the sensor,modifying 4 mmol/L thionin molecules to provide redox signals,and finally adding molecular-imprinted polymer drops.The surface morphology of the sensor was clearly visible and the chemical composition was confirmed,indicating that the sensor has been successfully prepared.Under the optimal preparation conditions,the sensor showed super-sensitive response to betaine detection in the range of 1 ～ 10 mmol/L,the detection limit was 0.707 fmol/L(S/N = 3),and had good selectivity,stability and repeatability.2.A dual-channel screen-printed electrode was used as the substrate electrode,and 1mg/m L chloroauric acid solution was used to generate gold nanoparticles on the surface of the sensor to improve its electrical conductivity and active area.5 mg/m L chitosan and 180 mg/m L glucose oxidase were mixed to improve the enzyme loading and activity.10% Nafion aqueous solution was added to increase cation selectivity and improve electrode stability.On this basis,a dual-channel electrochemical sensor was developed for the detection of glucose content in plant flat leaves in vivo.The morphology,structure and electrochemical characterization of the sensor for glucose detection in plant leaves showed that the electrode was successfully prepared,and it had a good catalytic effect on glucose.The reaction was a diffusion control process.The linear detection range of the two-channel sensor for glucose detection in living plant leaves was 1-150 mmol/L and the detection limit was 0.784 mmol/L,the sensor also showed good selection performance and stability.3.The real sample recovery of cucumber juice was tested.The results showed that the recovery rates of the betaine sensor were 96.78% ～ 106.74%,and the recovery rates of the glucose sensor were 97.17% ～ 103.05%,which indicated that the two sensors were accurate and reliable.Betaine sensor was used to detect the content of betaine in living cucumber leaves under salt stress,and the results showed that the content of betaine under salt stress was three times that under normal conditions.Meanwhile,the relevant detection data were compared with the results of high performance liquid chromatography,which had similar and the same trend of change.The glucose sensor was used to detect the glucose content in cucumber leaves under downy mildew infection condition.The results showed that the sensor could accurately identify the glucose changes in different infected areas,so as to obtain the corresponding changes in glucose content under different physiological environment.Both kinds of sensors show good application value in actual samples and living plants,and have broad application prospect in precision agriculture. |
