Research Of Far-red/nir BODIPY-based Fluorescence Probes With Disaggregation-induced Emission Property For Biomolecular Recognition

Molecular recognition is a prcocess in which host moleculars selectively bind to guest moleculars and exert specific functions.It is a specific interaction and is one of the important ways for molecules to self-assemble into advanced structures.It has broad application potential in the detection of molecular ions,drug controlled release,and the development of nanomaterials.Molecular recognition is usually accomplished through non-covalent bonds,and often requires special media to be monitored.Fluorescent probe can convert the information of molecular recognition process into fluorescent signals that are easy to detect,with the advantages of high sensitivity and low detection limit.It can realize real-time and in-situ detection.Therefore,fluorescent molecular probe with fluorescence as the output signal has become a research focus and is widely used in cell imaging,biomimetic fluorescent materials,environmental monitoring,biomolecular ion detection,disease diagnosis and other fields.However,the aggregation-induced quenching(ACQ)effect which is common in the application of fluorescent probe,seriously hinders their application in the field of biosensors.It may be advantageous when it is applied in the opposite way,such as disaggregation induced emission(DIE).DIE provides a new idea for reducing the adverse effects of ACQ.This type of probes often aggregates in aqueous solution,leading to fluorescence quenching,and disaggregates after binding to guest,leading to fluorescence signals recover or enhance.This signal amplification process can reduce the interference of background noise and has higher sensitivity.It can be applied to the design of“off-on”fluorescent probe and has good development potential in the field of biosensors.The main skeleton commonly used for DIE fluorescence probe are cubic acid,cyanine and fluoboropyrrole(BODIPY).Among them,BODIPY has the advantages of low biotoxicity,high fluorescence quantum yield,good photothermal stability,easy structure modification,and has been widely used in biological imaging,photodynamic therapy and photothermal therapy research.This paper designed and synthesized new types of deep red/near infrared D-π-A fluorescent probes using fluoroboropyrrole as fluorescent parent.Functional groups were introduced to regulate the structure and optical properties.This provided ideas,methods and related research results for the construction and biological application of aggregation-disaggregation probes.The main research results are as follows:(1)Serum Albumin(SA)plays an important role in maintaining osmotic pressure,inhibiting platelet aggregation and anticoagulation,so the detection of SA is of great significance.Therefore,this chapter constructed a class of fluoroboropyrrole fluorescence probes by DIE to detect serum albumin.The probe P-1 was obtained by introducing a phenol hydroxyl group at the meso site and an aryl vinyl group at theβsite.Compared with the parent molecule F-1,the absorption and emission wavelengths of probe P-1 were significantly extended.The maximum absorption peak was 585～610nm,and the maximum emission peak was 625～725nm,showing a larger Stokes shift(38～97 nm).Probe P-1 obviously aggregated in water with almost no fluorescence and very low background.When P-1 combined with SA,the aggregates disaggregate and the fluorescence recovers,while the parent molecule F-1 was not observed the process of aggregation and disaggregation.TEM and DLS experiments further proved this process.Probe P-1 showed good selectivity for SA among amino acids,proteins and active small molecules.We further explored the binding mechanism between P-1 and SA,by means of fluorescence quenching experiments,three-dimensional fluorescence spectrum,fluorescence replacement experiments,circular dichroism chromatography and molecular docking simulation.The fluorescence quenching mechanism explained that P-1 interact with SA by dynamic and static mixing mechanism.The combination of P-1 and SA mainly affected the microenvironment around tyrosine residues,and the binding site is in the IB region of SA.(2)G-quardruplex(G4 DNA)is closely related to physiological processes such as cell proliferation,cell apoptosis,and the occurrence of cancer.Therefore,it is of great significance to develop selective probes of G-quardruplex.However,due to the structural complexity of G-quardruplex,few probes can detect specific G-quardruplex.In this chapter,we based on the DIE mechanism designed a fluoroboropyrrole probe MRY-3 which can identify c-MYC G4 DNA selectively.The meso site of the BODIPY parent nucleus was connected to bipyridine,and the para-amino side chain was introduced at theβsite.In water,probe MRY-3 exhibited an aggregation state with low fluorescence intensity,while in organic solution,it existed a monomer form with bright red fluorescence.The addition of c-MYC G4 DNA can induce the disaggregation of probe aggregates,and significantly increase the fluorescence intensity of probe MRY-3 by more than 140 times.The fluorescence intensity showed a good linear relationship with the concentration of c-MYC in the range of 0～1.6μM(R~2=0.9996),and the detection limit was 22 n M.Compared with other configurations of G4 DNA and non-G4 DNA,MRY-3 showed higher selectivity for c-MYC G4 DNA.Base mutation experiments and molecular docking simulation calculation explained that MRY-3 binds to the groove of c-MYC G4 DNA.Cell experiment showed that MRY-3 can enter cells and exist in the cytoplasm with good biocompatibility.