Application Of Fluorescent Carbon Quantum Dots To Bioactive Substances

In a normal physiological state,there is a dynamic balance between oxidation-active species and reduction-active species in human cells to maintain the body’s metabolism.Among them,the most representative bioactive substances fall into three categories,including Reactive Oxygen Species（ROS）,Reactive Nitrogen Species（RNS）and Reactive Nitrogen Species（RSS）.Once the imbalance of REDOX homeostasis in cells is found,especially the excessive ROS and RNS,it often predicts the production of diseases,such as cancer,Alzheimer’s disease,cardiovascular disease,diabetes and pathological aging.Therefore,monitoring the level of bioactive substances is of great significance for the early diagnosis and treatment of related diseases.In this dissertation,Cl O^-,ONOO^-and H₂S are selected as typical ROS,RNS and RSS research objects,aiming to develop functionalized carbon quantum dots（CDs）as specific fluorescent probes to conduct fluorescence sensing application research on bioactive substances and monitor the levels of related bioactive substances in cells.We will explore the interaction and detection mechanism between CDs,ROS,RNS and RSS,so as to lay the foundation for early diagnosis and treatment of related diseases.This dissertation is divided into four chapters,aiming at developing functional CDs,constructing fluorescence sensing methods for bioactive substances Cl O-,ONOO-and H₂S respectively,and expanding the application of CDs in the field of life science.Chapter 1 gives an overall introductionfor the preparation method,properties,luminescence mechanism,functionalization method and application of CDs.In addition,their applications in chemical sensing,biological imaging and medical treatment are also discussed.At the same time,the relevant research progress of bioactive substances is briefly introduced.It is important to discuss the interaction and detection mechanism of CDs with ROS,RNS and RSS for the early diagnosis and treatment of related diseases.In Chapter 2,the application of functional CDs to the fluorescence sensing of Cl O^-is studied.Using Pyronine Y as carbon source,a green fluorescent probe PY-CDs-1 was designed and synthesized by hydrothermal method,which can specifically recognize Cl O^-.PY-CDs-1has excellent photostability,outstanding chemical stability and strong anti-salinity ability.Its fluorescence is not interfered by other ions and active oxygen components,which is suitable for the cell imaging study of Cl O^-in vivo.Cl O^-with strong oxidation ability can destroy the relatively stable aromatic ring structure of PY-CDs-1 instantaneously and quench the green fluorescence of PY-CDs-1.In order to enhance the visual detection effect,we combined PY-CDs-1 emitting green fluorescence and Ru（bpy）₃²⁺emitting red fluorescence to construct a ratio probe,which can realize the obvious"green-to-red"fluorescence visualization effect on Cl O^-,and this method has very good selectivity.As a fluorescent probe for specific recognition of Cl O^-,PY-CDs-1 has a broad application prospect.In Chapter 3,functionalized CDs of ONOO^-fluorescence sensing application research.Using safranine T as carbon source,an orange fluorescent probe T-CDs which can recognize ONOO^-was synthesized by hydrothermal method.The fluorescent probe PY-CDs-1 was covalent with T-CDs to obtain PT-CDs,which could emit green and orange fluorescence at the same time.ONOO^-could destroy the molecular structure of T-CDs,quench the orange fluorescence and cause the aggregation of PT-CDs,but the green fluorescence of PT-CDs was not interfered.Based on this,we construct a ratio fluorescence detection method for ONOO^-.The results show that the detection of ONOO^-by PT-CDs is stable in the range of p H 2～10.Moreover,at 1 M of high salinity,the effect of PT-CDs on ONOO^-fluorescence detection is not affected,which provides a guarantee for the next application of PT-CDs in the imaging detection of ONOO^-in cells.In Chapter 4,the functionalized CDs of H₂S fluorescence sensing application research.Using Pyronine Y as carbon source,we constructed a new fluorescent probe PY-CDs-2 which can emit both orange red and green fluorescence by regulating synthesis conditions,and used it for fluorescence sensing detection of intracellular active sulfur H₂S.The addition reaction between H₂S and Pyronine Y molecules adsorped byπ-πconjugation on the outer surface of PY-CDs-2 can quench the orange fluorescence.While the green fluorescence of the PY-CDs-2core remained basically unchanged,the fluorescence of the solution changed from yellow to green,which could realize the visual fluorescence detection of H₂S.At the same time,PY-CDs-2 was also successfully applied to the imaging detection of exogenous H₂S in He La cells and endogenous H₂S in MCF-7 cells.