Porphyrin-based Fluorescent Probes For The Detection Of Adenosine Triphosphate And Glucose

Porphyrins and their derivatives are a class of heterocyclic macrocyclic compounds that have a large extinction coefficient in the visible light region,large structural rigidity,and good chemical stability.Due to their structural characteristics,there are strong π-π stacking interactions,hydrogen bonding and electrostatic interaction in aqueous solution among porphyrin molecules,which may lead to aggregation among them.The aggregation behavior can cause different changes in their properties,such as shortened fluorescence lifetime,fluorescence quenching,blue or red shift of the absorption peak.However,the conventional biological analysis sensing system is aqueous solution environment.Therefore,how to optimize the design of porphyrinbased fluorescent probes to enable them to have excellent optical properites and stability in water medium is still a scientific problem to be solved.In order to avoid the aggregation of free porphyrin molecules in the aqueous solution,it can be introduced into the framework as a ligand.On the one hand,it provides a local hydrophobic environment for them,on the other hand,it can separate porphyrin molecules through coordination.As a special secondary structure,the G-quadruplex is stacked by multiple planar G-quadruplexes through a variety of interaction forces,and forms a hydrophobic channel with a negative charge in the middle,which provides structural support for the combination of ligands.In addition,metal-organic framework materials can also be used as frame due to their inherent advantages of large specific surface area,adjustable pore size,diverse spatial structure and flexible designability.In this dissertation,we chose two porphyrin molecules as the ligands and designed two fluorescent probes which were applied to construct fluorescent assay,respectively.This dissertation mainly includes the following three parts:（1）Two fluorescent probes based on porphyrin compounds（split Gquadruplex/PPIX and PCN-222（Zn））were prepared,respectively.Firstly,two DNA sequences GW3 and GW9 were designed to construct an enhanced fluorescent probe.Mainly,two free DNA strands can be close to each other with the help of the linker strand S,and folded into a G-quadruplex structure under the stability of K⁺,which can significantly enhance the fluorescence of protoporphyrin IX（PPIX）.Finally,we explored its potential application value in biosensing.In addition,Zn-5,10,15,20-tetra（4-carboxyphenyl）porphyrin（TCPP-Zn）was used as the organic ligand to prepare PCN-222（Zn）.We firstly studied the fluorescence properties and stability of PCN-222（Zn）.And then we explored the feasibility of fluorescence quenching by the oxidated pyrogallol.The above two fluorescent probes based on porphyrin molecules can overcome the aggregation among the porphyrin molecules in water and improve their optical properties.This chapter provides the experimental basis for the detection of adenine nucleoside triphosphate and glucose by the designed fluorescent probes.（2）The label-free split G-quadruplex fluorescent aptamer sensor for adenosine triphosphate（ATP）detection was designed with the constructed split G-quadruplex/PPIX as the output signal and ATP aptamer as the recognition element.Under the optimal conditions,this method had good sensitivity and was expected to be used for ATP detection in the serum of healthy people.The label-free fluorescent aptamer assay has high specificity and does not require complex and expensive fluorescent labeling of DNA.（3）A fluorescent/colorimetric dual-mode sensing strategy was designed using PCN-222（Zn）as a fluorescent probe and pyrogallol as a colorimetric probe for H₂O₂ and glucose detection.In this chapter,we used H₂O₂ to oxidize pyrogallol,and the obtained oxidation products significantly quenched the fluorescence of PCN-222（Zn）.Simultaneously,the reaction product of pyrogallol can be used as the signal for colorimetric detection,which can realize the detection of H₂O₂.The sensing of PCN-222（Zn）/pyrogallol to H₂O₂ provides a wide range of universal sensing and detection platforms for responding to any substance.As long as it involves the reaction that can produce H₂O₂.As a conceptive proof of this universal method,we introduced glucose oxidase into the system to achieve the detection of glucose.Under the optimized experimental conditions,the assay had excellent sensitivity and selectivity,which had the potential for detection in actual samples.