Design And Biological Applications Of Novel Fluorescent Probes Based On Cyanine Dyes

Cyanine dyes are widely used in the dyestuff industry,chemistry,medicine,and other fields.Due to their special photophysical properties and easy synthesis and modification ability,cyanine dyes have become ideal fluorescent platforms for the design of near-infrared（NIR）fluorescent probes for a variety of analytical targets including ions,bioactive species（ROS/RNS/RSS）,enzyme,cellular microenvironmental factors and so on.In this work,we introduce three fluorescent probes based on cyanine dyes and their biological applications.Nitric oxide（NO）is an important short-life reactive nitrogen species（RNS）synthesized by nitric oxide synthase（NOS）.Many studies have found that mitochondria play a crucial role in the production of NO.Therefore,the detection of NO in mitochondria is of great significance.We constructed a novel dual-channel NO fluorescent probe Mi-NO targeting mitochondria.At two excitation wavelengths,Mi-NO showed a significant spectral response towards NO,and it was verified by DFT calculation.In addition,molecular docking calculation and co-localization imaging results indicated that Mi-NO could accurately target mitochondria.Mi-NO successfully imaged exogenous NO in He La cells and zebrafish,which provides a potential tool for further exploring the role of NO in the biological system.Hypochlorite（OCl^-）is a well-known member of the reactive oxygen species（ROS）family.It plays an important antibacterial and anti-inflammatory role in the human immune system.However,the abnormal level of OCl^-may lead to the destruction of cell physiological structure,induce oxidative stress and lead to a variety of diseases.Based on the mechanism of internal charge transfer（ICT）process,we constructed a new ratiometric fluorescent probe Mi-OCl-RP.The probe could recognize OCl^-via ratio spectral change,and had the advantages of large Stokes shift and fast response which could be observed by the naked eyes.Molecular docking calculation was used to determine the possible binding sites between Mi-OCl-RP and potential molecular target ANT in mitochondria.The molecular docking mode showed the high affinity between the probe and mitochondrial ANT,which provided theoretical proof for the specific targeting ability of Mi-OCl-RP in mitochondria.The results of co-localization imaging also supported the efficient targeting ability of the probe to mitochondria.Finally,Mi-OCl-RP successfully performed ratio imaging of exogenous and endogenous OCl^-in living cells and zebrafish.Acute lung injury（ALI）is a severe pulmonary inflammatory disease with high morbidity and mortality,and it still presents a serious challenge in critical care medicine.So far,the specific pathogenesis of ALI is still under exploration,and the treatments or prevention options are limited.Hydrogen sulfide（H₂S）is a member of gas signal molecules.It can regulate nervous system and cardiovascular system,and play a key role in a variety of physiological and pathological activities.Although the imaging of exogenous H₂S added into cells and in vivo has been well studied,there are still open challenges in real-time tracking H₂S and exploring its related pathological activities at the cellular and tissue levels.Herein,we reported a fluorescent probe HCy-HSP based on a new sulfur-substitution hemicyanine dye,which could achieve a rapid and significant"turn-on"fluorescence response to H₂S.The quantitative imaging of endogenous H₂S under different stimulation conditions in normal/cancer cells had been realized by using HCy-HSP.In addition,HCy-HSP had also been successfully applied to fluorescence imaging of LPS-induced ALI model mice in vivo and ex vivo,proving it a promising molecular tool for exploring the role of H₂S in physiological and pathological activities.