Construction Of Near-Infrared Rhodol Probes For Biomedical Imaging

Fluorescence imaging has become one of the most important tools for medical diagnosis and drug screening due to its excellent spatiotemporal resolution,safety,and ease of use.Among them,fluorescence imaging in the near-infrared region(650-900 nm)has attracted much attention due to its high penetration,low phototoxicity caused by long-light excitation,and low tissue background interference caused by long emission.Based on conventional dye molecules such as cyanine dyes,large-π BODIPY,and long-emitting xanthene fluorophores,a variety of functional probes have been developed,which have great potential in drug screening and disease diagnosis.However,sensitivity to physiological environments(such as pH and albumin)and real-time imaging of analytes remain key issues in probe development,limiting their use in in vivo imaging.In order to solve the above problems,based on the molecular skeleton of the near-infrared Rhodol of the xanthene dye family,the halogen bond was rationally introduced ortho to the electron acceptor of fluorescent dyes to develop novel fluorescent probes for biomedical imaging.Two aspects were included:1.A pH-insensitive near-infrared dye molecule(pH 5-12)was synthesized and screened by rationally introducing an ortho-halogen bond at the ortho position of the electron acceptor of the dye molecule to adjust the balance of protonation and deprotonation.Based on this dye,a near-infrared fluorescent probe2F-RBH was constructed,which provided a stable signal in the gastrointestinal tract with dynamic pH changes;2.The effect of the introduction of ortho-halogen bonds on the reactivity of the probes was systematically studied.A novel fluorescent probe 2F-RBX was constructed based on the near-infrared dye molecules screened in the Chapter II.Studies have shown that the introduction of an ortho-halogen bond can induce an ortho-inductive effect,reduce the thermal stability of the probe molecule,and significantly shorten the detection time of biothiols(within 5 minutes).Furthermore,2F-RBX was successfully used for rapid detection of endogenous biothiols in HepG-2 cells and visualization of drug-induced liver injury(DILI)in mice.These results suggest that the rational introduction of ortho-halogen bond in electron acceptor of dye molecules is a simple and flexible strategy to construct pH-insensitive near-infrared fluorescent probes and improve probe reactivity,realizing real-time detection of analytes.Also,our study can provide a research basis for the development of other near-infrared fluorescent probes for real-time imaging of analytes in the complex biological environments of organisms.The near-infrared fluorescent probe developed in this study is expected to become an effective tool for the study of redox-related diseases,drug screening and efficacy evaluation.