Study On Screening Electrode Modified By Spermidine Molecular Imprinting Film

This paper aims to develop a sensor based on molecular imprinted technology(MIT) and establish a new method to detect Spermidine(SPD) by this sensor. The molecular imprinted polymer with specific adsorption ability for SPD was filmed on the surface of screen printing electrode, which was applied to detect spermidine.The spermidine molecularly imprinted polymer is based on computational chemistry research.The binding energy of the imprinted molecule with functional monomer was calculated by the density functional theory(DFT)method. The monomer that provided the largest binding energy was then chosen for the synthesis of molecular imprinted polymers. The calculation showed that methacrylic acid had largest binding energy with SPD in the widely used eight kinds of functional monomers,which demonstrated the highest stability. The lowest energy of the composite composed of MAA and CAN demonstrated the lowest stability.Studies on the complex system composed of SPD and MAA showed that the monomer and template with molar ratio of 1:5formed 6 hydrogen bonds possessed the lowest energy and combined most stably.Meanwhile, the amount of hydrogen bonds between the monomer and template wouldn’t increase even with the molar ratio of over 1:3. What’s more, the largest energy increment reached 56.5519048 k J/mol when the molar ratio increased from 1:3 to 1:4. The energy increment was only 48.142480735 k J/mol while the molar ratio increased from 1:4 to 1:5, and the amount of hydrogen bonds didn’t increase.Ultraviolet spectrum scanning was employed to collect spectroscopic data of different complex systems composed of SPD and three different monomers. The result agreed with computational chemistry research, which also demonstrated that MAA and SPD could form the most stable coumpound. Differential ultraviolet spectral analysis showed that one SPD molecule could conjugate with three different monomers to form SPD-3MAA, SPD-3AM and SPD-3AA,respectively, which explained that one SPD molecule needs to conjugate with at least three monomers to form stable compounds. The result was the same as computational chemistry research, which demonstrated that SPD and the monomers could form stable compounds only when the molar ratio was over 1:3.The characterization of spermidine-molecular imprinted polymer showed that the polymercomposed of SPD and MAA with the molar ratio of 1:4 possessed the best adsorption performance and selectivity. The polymer with the molar ratio of 1:3 took the second place. The polymer with the molar ratio of 1:5 showed worst. The adsorption processes of three different polymers were in accordance with pseudo-second-order kinetic model. The Scatchard curve showed there are two different types of adsorption sites in SPD-MAA with the molar ratio of 1:4. At this molar ratio, the maximum adsorption amount was 97.75 μmol/g, the dissociation constant was 0.651 μmol/L. The adsorption amount for TRY and HIS were 2.01 and 1.78, respectively. The performance of the polymer at this ratio was better than that of other ratios.At last, the preparation and characterization of the spermidine-molecular imprinted polymer modified screen printing electrode were carried out. This part aims at coupling optimized polymer material and function electrode. SPD-MAA with the molar ratio of 1:4 was employed as film-forming components of the sensor. Spermidine-molecular imprinted polymer was prepared on the surface screen printing electrode by Uv polymerization. Then eluting template for 4200 s.The adsorption equilibrium time of this electrode was 360 s. The results showed that the MIPs electrochemical sensor not only possessed specific adsorption and high recognition capacity toward SPD but also could be used to detect it in the concentration range between 1×10-6- 6×10-6mol/L and detection limit of 1.7016×10-7 mol/L. The linear equation was y=-1.223x+7.8197(R2=0.9952).The special functional electrode for detecting SPD was prepared by the aforementioned research. This method for rapid detection of the SPD promoted the combination of MIT and electrochemical detection technology, which was important for new test method of SPD.