Research On The Application Of Molecularly Imprinted Polymers Based On Graphene Quantum Dots In The Detection Of Small Biological Molecules

Molecularly imprinted polymers?MIPs?have special binding sites to re-recognize template molecules and are used as tailor-made advantageous materials.They are generally prepared by the covalent imprinting approach,non-covalent imprinting approach and other methods.At present,molecular imprinting technology has been widely applied in many fields of chemistry,biochemistry and biotechnology.Graphene Quantum Dots?GQDs?is a quasi-zero-dimensional nanomaterial of carbon-based quantum dots,which not only has good fluorescent properties,but also has the advantages of high solubility in water,low biological toxicity,high stability,large surface area.Moreover,the delocalized?-electron system with large GQDs provides GQDs with a strong affinity for species containing aromatic rings,which not only makes it possible to adjust the electronic band structure and the optical properties of GQDs through non-covalent modification,but also allows GQDs for further functional modification.In this thesis,polypyrrole and polydopamine modified graphene quantum dot molecularly imprinted polymers were prepared,which were used to detect biological small molecules adrenaline and glutathione,respectively.We studied the fluorescent properties of the materials and evaluated the detection effect using by the changes in their fluorescent properties.Moreover,the in vitro uptake and detection effect of Ppy/GQDs-MIP and PDA/GQDs@MIPs were researched.This thesis is divided into four chapters.In the first chapter,we briefly talked about the current status of molecular imprinting technology,the basic principles and construction strategies of molecular imprinting-fluorescence sensors.At the end of this chapter we bring up the research topic of this dissert.In the second chapter,we prepared Ppy/GQDs-MIP.By using the non-covalent interactions such as electrostatic interactions,?-?stacking,and hydrogen bonding between GQDs and adrenaline?Ad?,GQDs,Ad and polypyrrole were assembled during polymerization of pyrrole.Ppy/GQD-MIP was obtained after removing the template molecules.GQDs as a base material can be modified with polypyrrole function to passivate the surface of it.After breaking the hydrogen bond in acidic environment to remove template molecules,GQDs can still show excellent fluorescence properties.Therefore,we used the electron transfer between GQDs and Ad in Ppy/GQDs-MIP to cause fluorescence quenching to detect Ad.Through a series of material characterization and experimental optimization,the detection effect of Ppy/GQDs-MIP on Ad at the solution level and the cell level was evaluated.The detection had a wide linear range with a detection limit of 4.7?M.In the third chapter,based on chapter two,we used non-covalent interactions such as electrostatic interactions and hydrogen bonding between GQDs and glutathione?GSH?to assemble GQDs,GSH and polydopamine under dopamine polymerization conditions.The template molecules were removed by breaking hydrogen bond in an acidic environment to obtain PDA/GQDs@MIPs,which showed good fluorescence properties.Therefore,the electron transfer between GSH and PDA/GQDs@MIPs can cause fluorescence quenching to detect glutathione.Through a series of material characterization and experimental optimization,the detection effect of PDA/GQDs@MIPs on GSH at the solution level was investigated and the detection limit was 1.3?M.The difference in the content of GSH in normal cells and tumor cells can be detected at the cell level.In chapter four,we designed a fluorescent switch for detecting Ascorbic Acid?AA?.Because GQDs have many oxygen-containing groups,which can transfer electrons to Fe³⁺coordination,which will cause GQDs fluorescence quench.When different concentrations of ascorbic acid were further added to GQDs-Fe³⁺,ascorbic acid can undergo a redox reaction with Fe³⁺and reduce Fe³⁺to Fe²⁺,which destroyed the coordination between the original Fe³⁺and the oxygen-containing group,thereby making GQDs recovered fluorescence.Therefore,changes in the fluorescence intensity of GQDs-Fe³⁺can be used to detect ascorbic acid.There was an obvious linear relationship,and the detection limit based on the fitted equation was 0.27?M.In the last chapter,we summarized the experimental results obtained in this paper,analyzed and discussed the advantages and disadvantages of these work.The future development of the MIP materials was also involved.