Design And Synthesis Of Near Infrared Excitated Fluorescent Probes Based On Engegy Transfer And Their Application In Bioimaging And Detection

The development of fluorescent technology provides a convenient method for rapid,sensitive,and specific detection of specific molecules.A large number of fluorescent probes have been developed for environmental detection,food safety,explosion monitoring,bioimaging,disease diagnosis,and real-time tracking.The use of molecular recognition to generate fluorescent responses for detection is one of the areas where analytical chemists have made significant progress,and it has shown great potential in further applications.The use of analyte-reponsive fluorescent probes for the detection of life-related molecules is important for further understanding of working mechanisms,physiological processes,and life activities of these molecules.In addition,it is important to use fluorescent technology to in situ detect the harmful molecules in the environment.However,the exitation and/or emission of most traditional fluorescent probes are in the visible region,which have the disadvantages of large biological background fluorescence,limited tissue penetration depth,short Stokes shift and photobleaching,thus limiting their applications for in vivo and rapid detection in complex environments.In order to better solve these problems,development of fluorescent probes with better performance is still one of the area we need to work on.Compared with traditional fluorescent probes,near-infrared fluorescent probes have deep tissue penetration depth,transparency with biological background fluorescence and resistance to external environmental interference.Therefore,the development of near-infrared fluotescent probes is currently a hot topic.However,near-infrared small-molecule probes still have limitations such as excitation light interference,short Stokes shift,and requirement of large-scale instrument for signal readout.Therefore,designing a composite probe that combines multiple luminophores for energy transfer to solve the above problems is the hot spot of current research.In this thesis,we start with the advantage of that the near-infrared fluorescence could reduce biological background and excitation light interference,improve detection sensitivity,and we combine the two-photon fluorescence resonance energy transfer imaging technology and dye sensitization up-conversion strategy to construct a series of novel probes with high sensitivity,rapid response,good selectivity,and reduced environmental disturbance.They were applied for detection and imaging of harmful organic molecules and biogically active small molecules by the naked eye.The details are as follows:(1)Design and synthesis of mesoporous silicon nanoparticles probe,MSNFITCDNS,with near-infrared excitation,for detection and imaging of Sec in cells and tissues mediated by the fluorescence resonance energy transfer mechanism.In Chapter 2,we used the easy-modification c haracter of mesoporous silicon nanoparticles to integrate two dye fluorophores into a single nanoparticle.Under the excitation of two-photon laser,the dimethylaminonaphthoic acid-based fluorophore acts as a donor of fluorescence resonance energy transfer,which can increase the depth of tissue penetration.The FITCDNS with FITC modification can specifically response to Sec,which could,after the reaction,act as a receptor for fluorescence resonance energy transfer,accept the energy of dimethylaminonaphthoic acid,and produce rariometric fluorescent changes.The design can effectively achieve the two-photon fluorescence resonance energy transfer for ratiometric detection of selenocysteine,with increased Stokes shift and thereby reduced interference from environmental factors.Thus,rapid and stable detection of selenocysteine and deep tissue imaging(about 120 ?m)in a complex biological environment are achieved.(2)Specific detection of phosgene by a near-infrared fluorescent probe based on cyanine.Phosgene is widely used for its commercial value but also a toxic molecular.However,it is highly hazardous,and its leakage or misuse can lead to serious consequences and pose a great threat to human health.Current fluorescent probes used for phosgene detection are based in visible region.These probes are susceptible to ambient interference and excitation light interference.Therefore,in Chapter 3,we developed a cyanine-based near-infrared fluorescent probe for specific detection of phosgene.We modified ethylenediamine on IR783 to synthesize CyNN.Due to the ICT effect of ethylenediamine,CyNN has no emission at 820 nm.The ethylenediamine structure can specifically respond to phosgene rapidly,forming a five-membered ring structure,and then the ICT disappears,which makes the fluorescence at 820 nm significantly enhanced.The probe enables fast and sensitive detection of phosgene with a detection limit of 3.4 nM.(3)Although the small-molecule fluorescent probe based on near-infrared dye has the advantages of resisting external environmental interference,it also has the inherent limitations,that is,near-infrared light cannot be catched by the naked eye.Therefore,all current near-infrared fluorescent probes require instruments to record the results.In the fourth chapter,we modify the CyNN develped in chapter 3 onto the surface of the lanthinade ion-doped unconversion nanoparticles(UCNP-Nd@CyNN).Using the dye-sensitizating strategy,the near-infrared emission of CyNN is converted into the visible emission of lanthinade ion-doped unconversion nanoparticles.This detection enables directly observing the response of the near-infrared fluorescent probe CyNN by the naked eye.Moreover,since the near-infrared light cannot be observed by the naked eye,that is to say,the near-infrared excitation light has zero background to the naked eye,and the signal can be observed even though the signal is weak.By this strategy,a highly sensitive detection of phosgene is achieved,with a detection limit of20 nM.(4)Upconversion nanoparticle,as a promissing luminescent material,is widely used in detection and imaging.However,most of the current detection methods based on up-conversion nanoparticles are mediated bythe mechanism of quenching and recovery.However,due to the intrinsic limitation of this mechanism,the probes of the up-converting nanoparticles have a background,which has effects on detection limitation and the accuracy of detection.In Chapter 4,we design the probe using a dye sensitization strategy with low background.In the chapter 5,we further improve the dye-sensitizing unconersion system(UCNP-Yb@820NN)based on IR820 and Nd-free UCNPs,whichis phosgene-sepecfic up-conversion nanoparticle probe with nearly zero background.