A New Heptamethine Cyanine-Based Near-Infrared Fluorescent Probe for Divalent Copper Ions with High Selectivity

A new near-infrared fluorophore 2-(2-Aminoethyl) pyridine-tricarbocyanine (1) was rationally designed and synthe-sized as a fluorescent probe for detection of Cu2+ with high selectivity. The response of Probe 1 is based on the fluorescence quenching upon binding to Cu2+. The sensing performance of the proposed Cu2+-sensitive Probe 1 was then investigated. The probe can be applied to the quantification detection of Cu2+ with a linear concentration range covering from 4.8 × 10-7 to 1.6 × 10-4 mol/L and a detection limit of 9.3 × 10-8 mol/L. The experimental results showed that the response of 1 to Cu2+ was independent of pH in medium condition (pH 6.0-8.0), and exhibited excellent selectivity towards Cu2+ over other common metal cations.

A near-infrared fluorescent probe for visualizing transformation pathway of Cys/Hcy and H2S and its applications in living system

Sulfydryl-contained(-SH)substances including hydrogen sulfide(H_(2)S),cysteine(Cys),homocysteine(Hcy)and glutathione(GSH)play crucial roles in living systems,and their variations are closely associated with various diseases.Herein,we developed a near-infrared intramolecular charge transfer(ICT)based fluorescent probe Y-NBD,achieving detection of Cys/Hcy and H_(2)S with different fluorescent signals(green-red for Cys/Hcy,red for H_(2)S),large Stokes shifts(∼100/105nm or 191 nm)and high signal-background-ratio,but not responding to GSH.Y-NBD was successfully applied to image exogenous/endogenous Cys/Hcy and H_(2)S in various living cancer cells(HeLa,A549,and HepG2)and in zebrafish.It not only visualized the transformation pathway of several thiols in HepG2 cells but also verified that the intestine is the main site for the activation and metabolism of Y-NBD in zebrafish,as well as realized to evaluate the degree of drug-induced liver injury.This work provides a promising tool for imaging Cys/Hcy and H_(2)S in living systems and shows great potency in evaluating drug-induced liver injury and its treatment.

Responsive mechanism and molecular design of di-2-picolylamine-based two-photon fluorescent probes for zinc ions

The properties of one-photon absorption（OPA）, emission and two-photon absorption（TPA） of a di-2-picolylaminebased zinc ion sensor are investigated by employing the density functional theory in combination with response functions.The responsive mechanism is explored. It is found that the calculated OPA and TPA properties are quite consistent with experimental data. Because the intra-molecular charge transfer（ICT） increases upon zinc ion binding, the TPA intensity is enhanced dramatically. According to the model sensor, we design a series of zinc ion probes which differ by conjugation center, acceptor and donor moieties. The properties of OPA, emission and TPA of the designed molecules are calculated at the same computational level. Our results demonstrate that the OPA and emission wavelengths of the designed probes have large red-shifts after zinc ions have been bound. Comparing with the model sensor, the TPA intensities of the designed probes are enhanced significantly and the absorption positions are red-shifted to longer wavelength range. Furthermore, the TPA intensity can be improved greatly upon zinc ion binding due to the increased ICT mechanism. These compounds are potential excellent candidates for two-photon fluorescent zinc ion probes.

A near-infrared fluorescent probe for fast and precise imaging of senescent cells and ovarian cancer cells via trackingβ-galactosidase

Aging-related diseases are gradually becoming a major problem with the rapid development of aged population in human society.Although many fluorescent probes have been employed to diagnosis senescence via imaging senescence-associatedβ-galactosidase(SA-β-Gal),which is proved to be closely associated with senescent cells,the similar catalytic effectiveness of enzymatic reaction of ovarian cancer-associatedβ-Gal(OA-β-Gal)will interfere with imaging accuracy.Herein,a near-infrared(NIR)hemicyanine based fluorescent probe HCyXA-βGal was designed for light-up imaging of live cells containingβ-Gal.With the organelle-targeting morpholinyl and positive charge moieties,HCyxA-βGal was successfully applicated to image the difference of enzymatic location in senescent cells and ovarian cancer cells.Furthermore,inspired by the fast response performance,fast and precise imaging of the two cell lines was realized via covering another dimension of fluorescence signal:time-dependent intensity.

Syntheses and properties of photostable near-infrared cyanines and their cyclodextrin conjugates

Three fluorescent indocyanines containing p-carboxybenzyl groups on N atoms in the heterocyclic tings were synthesized under supersonic. The maxima wavelength of the absorption and emission of the dyes were 550-800 nm in water. Compared with those in aqueous solutions, the fluorescence intensity of the dyes in the α/β-cyclodextrin, Al^3＋, Zn^2＋, Sn^2＋ or the α/β-cyclodextrin in the aqueous solutions of the cations became stronger. The crystal Shapes of the dyes and their cyclodextrin inclusions were mostly acicular or polygon. The NHS-carboxyl squarylium indocyanine was prepared and used to conjugate with taurine or benzylamine, the results indicated that the dyes could couple covalently to biomass containing free NH2 group. Structure and some thermal parameters of the molecule of the trimethine cyanine were obtained by DFT method of Gaussian O3.

用于肼检测的新型芘基荧光分子探针的合成与性能

利用1-芘甲醛优良的荧光性质,将其作为母体进行基团修饰,经过^(1)H-NMR和HRMS对结构进行表征,证实成功构建了肼荧光分子探针PMIDO。在DMSO-H2O体系中,PMIDO只能显示弱的荧光;在加入肼后,在含水量70%的条件下,显示出强的蓝色荧光,呈现出开灯型的荧光探针特征,检出限可达1.41×10^(-7)mol/L。同时,该探针对肼的检测呈现出高选择性和稳定抗干扰性,适用于5~10的pH范围,并在30 s内完成响应。进一步阐述了其荧光检测机制,即与肼反应后生成腙,为反应型肼的荧光检测提供有益参考。

Near-infrared fluorescent probes for imaging of amyloid plaques in Alzheimer's disease

One of the early pathological hallmarks of Alzheimer's disease(AD) is the deposition of amyloid-β(Aβ) plaques in the brain. There has been a tremendous interest in the development of Aβ plaques imaging probes for early diagnosis of AD in the past decades. Optical imaging, particularly near-infrared fluorescence(NIRF) imaging, has emerged as a safe, low cost, real-time, and widely available technique, providing an attractive approach for in vivo detection of Aβ plaques among many different imaging techniques. In this review,we provide a brief overview of the state-of-the-art development of NIRF Aβ probes and their in vitro and in vivo applications with special focus on design strategies and optical, binding, and brain-kinetic properties.

A ratiometric near-infrared naphthalimide-based fluorescent probe with high sensitivity for detecting Fe^(2+)in vivo

Iron is one of the essential trace elements in the human body.It plays an important role in human biology and pathology.Deregulation of iron levels in cells is associated with disease development.In this work,we synthesized a novel near-infrared intramolecular charge transfer(ICT)based ratiometric fluorescent probe to detect Fe^(2+),by using naphthalimide and indole moieties as building blocks.Our work showed that the radiometric probe has excellent selectivity,sensitivity and rapid response.Moreover,we could successfully perform real-time monitoring of Fe^(2+) in He La cells and C.elegans.

Molecularly near-infrared fluorescent theranostics for in vivo tracking tumor-specific chemotherapy

Molecularly near-infrared(NIR) theranostics, combining in vivo sensing and tumor-specific therapeutic capability within one molecular system, have received considerable attention in recent years. Compared with the visible fluorescence imaging, NIR imaging(emission wavelength at 650–900 nm) possesses unique advantages including the minimum photodamage to biological samples, deep penetration, and low interference from auto-fluorescence. In over past decades, there has been an explosive development in the design of molecular imaging contrasts and imaging-guided therapeutics. In this review, we have sumarried the strategies of the NIR theranostics for imaging and tumor-specific chemotherapy applications in living systems. It is noted that the molecularly NIR theranostic design strategy could address current challenges of real-time in vivo sense-and-release for the intelligent biosensing and personalized treatment.

Near-Infrared mitochondria-targeted fluorescent probe for cysteine based on difluoroboron curcuminoid derivatives

Curcuminoid difluoroboron has attractive performance as a promising near-infrared（NIR） fluorescent dye. In this contribution, we designed and synthesized a mitochondria-targeted NIR fluorescent probe DFB1 based on difluoroboron curcuminoid scaffold for the detection of Cys（cysteine）. DFB1 employs a curcumin analog as the NIR fluorophore, an acrylate group containing a, b-unsaturated ketone as a functional trigger moiety for Cys, and a triphenylphosphonium（TPP） cation moiety for specifically targeting mitochondria. The remarkable shift of DFB1 with Cys was observed from 470 nm to 590 nm in absorption spectra and from 560 nm to 680 nm in emission spectra. Notably, DFB1 manifests significantly dual-channel and turn-on NIR fluorescent signals simultaneously in response to Cys concentration,which make it favorable for monitoring endogenous Cys activity in vivo. This probe has high sensitivity and selectivity for the detection of Cys over homocysteine（Hcy） and glutathione（GSH）. This specific response for Cys was based on differences kinetics of intramolecular adduct/cyclizations. More importantly, biological experiments indicated that this probe could be utilized for the detection of endogenous mitochondrial Cys in living cells.

Two near-infrared highly sensitive cyanine fluorescent probes for pH monitoring

Two near-infrared（NIR） p H-activated heptamethine indocyanine probes with quaternary ammonium unit were designed and synthesized. The absorption and emission titrations indicate that cationic structure improves the cyanine dye＇s aqueous solubility and these two probes exhibit highly sensitive response to p H in acid condition. Their fluorescence intensities both gradually increase about 25-fold from p H 7.60 to 3.00 with p Ka values of 4.72 and 4.45 respectively, which are suitable for studying acidic organelles in living cells. Moreover, their fluorescence intensities are linearly proportional to p H values in the range of 5.50–4.00. These results are probably attributed to the protonation of the indole nitrogen atoms, which are verified by 1H NMR spectra. Furthermore, these two probes can achieve real-time imaging of cellular p H and detection of p H in situ in living He La cells due to their excellent properties,including good reversibility, desirable photostability, high selectivity, low cytotoxicity and remarkable membrane permeability.

A near-infrared fluorescent probe for monitoring fluvastatin-stimulated endogenous H_2S production

Most reported fluorescent probes have limitations in practical applications in living systems due to the strong autofluorescence background,construction of probes with near-infrared（NIR） fluorescence emission is an accessible approach for addressing this challenge.We here designed a NIR fluorescent probe for monitoring the endogenous production of H2S in living cells.The designed probe showed significant NIR fluorescence turn-on response to H2S with high selectivity,enabling the sensitive detection H2S.Importantly,the probe could be applied in monitoring the endogenous production of H2S in raw 264.7 macrophages.This study showed that fluvastatin can promote the activity of cystathionineγ-lyase（CSE） for generation H2S.

An activatable ratiometric near-infrared fluorescent probe for hydrogen sulfide imaging in vivo

Ratiometric fluorescent probes hold great promise for in vivo imaging;however,stimuli-activatable ratiometric probes with fluorescence emissions in near-infrared(NIR)region are still very few.Herein,we report a hydrogen sulfide(H_2S)-activatable ratiometric NIR fluorescent probe(1-SPN)by integrating a H_2S-responsive NIR fluorescent probe 1 into a H_2S-inert poly[2,6-(4,4-bis-(2-ethylhexyl)-4 H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)](PCPDTBT)-based NIR semiconducting polymer nanoparticle(SPN).1-SPN shows"always on"PCPDTBT fluorescence at 830 nm and weak probe 1 fluorescence at 725 nm under excitation at 680 nm.The ratio of NIR fluorescence intensities between 725 and 830 nm(I_(725)/I_(830))is small.Upon interaction with H_2S,the fluorescence at 725 nm is rapidly switched on,resulting in a large enhancement of I_(725)/I_(830),which is allowed for sensitive visualization and quantification of H_2S concentrations in living cells.Taking advantage of enhanced tissue penetration depth of NIR fluorescence,1-SPN is also applied for real-time ratiometric fluorescence imaging of hepatic and tumor H_2S in living mice.This study demonstrates that activatable ratiometric NIR fluorescent probes hold great potential for in vivo imaging.

机器学习预测食品重金属检测中铜离子对汞离子荧光信号的干扰

目的:构建一个人工智能预测模型,在存在Cu^(2+)干扰的复杂食品检测环境下预测荧光探针对Hg^(2+)的选择性。方法:采用荧光探针技术结合7种先进经典的机器学习模型,预测分析存在Cu^(2+)干扰时探针对Hg^(2+)的选择性,并比较各模型的预测效果,选择最优模型。结果:基于分子二维描述符(molecular 2D descriptors,Mol2D)和极端梯度提升算法成功建立了在交叉验证和测试集中准确度为0.786和0.810的高效模型,在Cu^(2+)干扰下准确预判Hg^(2+)的探针选择性。结论:该模型通过选择性预判对Hg^(2+)荧光分子探针的设计进行改进,使Hg^(2+)荧光探针的设计更加高效可靠。

A NIR fluorescent probe for imaging thiophenol in the living system and revealing thiophenol-induced oxidative stress

Thiophenol(PhSH)is an important raw material for organic synthesis,while its high toxicity to organisms makes it an environmental pollutant.Therefore,it is crucial to accurately detect PhSH and explore its metabolic process in the living system.Herein,a near-infrared(NIR)fluorescent probe TEM-FB was developed for sensing PhSH with a turn-on fluorescent signal at 719nm and a large Stokes shift(198 nm)based on generating the intramolecular charge transfer(ICT)process.TEM-FB shows high specificity and significant sensitivity towards PhSH(detection limit:10 nmol/L)via the aromatic nucleophilic substitution mechanism.Furthermore,it was successfully applied to image PhSH in multiple cell lines and in zebrafish.Notably,we revealed the oxidative stress process caused by PhSH and demonstrated that the hydrogen peroxide(H_(2)O_(2))in cells would alleviate the poisonousness from exogenous PhSH for the first time.This work provides a promising bioimaging tool for monitoring PhSH in living systems and visualizing the process of oxidative stress induced by PhSH.

多色比色法在生物传感平台的研究进展

比色法是生物传感中较为常用的一种检测手段,因其具有较高的灵敏度和特异性而受到广泛关注。其中,基于多色探针的多色比色法已成为近年来的研究热点,灵敏度较单色比色法显著提高、且具有更高的分辨率和肉眼辨识度,通过观察颜色变化可进行可视化半定量检测,又可通过计算颜色比率或基于智能手机图像处理软件进行快速定量检测。基于有机小分子荧光显色、纳米材料显色及酶促反应显色3种不同的显色机理,综述了多色荧光小分子探针、多色纳米材料比色探针及多色酶促反应比色探针的检测机理以及它们在实际样本检测中的应用,并进一步探讨了其面临的挑战及未来发展机遇。

Activatable molecular fluorescence probes for the imaging and detection of ischemic stroke

The real-time, noninvasive, nonionizing, high spatiotemporal resolution, and flexibility characteristics of molecular fluorescence imaging provide a uniquely powerful approach to imaging and monitoring the physiology and pathophysiology of ischemic stroke. Currently, various fluorescence probes have been synthesized with the aim of improving quantitative and quantitative studies of the pathologic processes of ischemic stroke in living animals. In this review, we present an overview of current activatable fluorescence probes for the imaging and diagnosis of ischemic stroke in animal models. We categorize the probes based on their activatable signals from the biomarkers associated with ischemic stroke, and we present representative examples of their functional mechanisms. Finally, we briefly discuss future perspectives in this field.

Self-adaptive non-covalent albumin-binding near-infrared probe conjugates enabling precise sentinel lymph node metastasis illumination and primary tumor imaging

Tumor sentinel lymph node(SLN)metastasis plays a vital role in tumor staging and therapeutic decision-making process.However,precise diagnosis of primary tumors and lymphatic metastases is still hindered by low imaging resolution and poor photostability of fluorescent probes.Herein,we report three novel IR820-fatty acid(FA)conjugates(IR-OA,IR-LA,and IR-PA)for precise lymphatic metastasis illumination and primary tumor diagnosis.The IR-FA conjugates are able to non-covalently bound to albumin in vivo,and the fluorescence quantum yield is significantly enhanced after incubation with bovine serum albumin(BSA)in vitro.Moreover,the BSA-IR-FA conjugates display large Stokes shift(>120 nm),dramatically improving in vivo imaging resolution.Among them,IR-PA demonstrates distinct advantage over IR-OA,IR-LA,and IR-maleimide(MAL)(fluorescent probe previously reported by our group)in terms of fluorescence quantum yield,photostability,and imaging resolution.As a result,IR-PA exhibits satisfactory imaging results with high fluorescence intensity and imaging resolution in sentinel lymph node metastasis illumination and primary tumor location.Our findings provide a self-adaptive albumin-binding near-infrared probe conjugate for accurate diagnosis of primary tumors and lymphatic metastases.

An activatable NIR-Ⅱ fluorescent probe for tracking heavy-metal ion and high-level salt-induced oxidative stress in plant sprouts

Humans and plants have become enfolded and inseparable.Abiotic stresses in particular oxidative stress caused by heavy-metal ions or high-level salt contamination deleteriously impact plants’growth process and have become a major threat to sustaining food security.Sprouting is the first step in plants’growth process.When plant sprouts endure oxidative stress induced by toxic heavy-metal ions or high-level salt,accelerated generation of reactive oxygen species(e.g.,H_(2)O_(2))occurs inside plant sprouts;hence in-situ H_(2)O_(2) in plant sprouts could serve as the in-vivo biomarker for tracking the oxidative stress in plant sprouts.Herein,we design an activatable probe CT-XA-H_(2)O_(2) to track the oxidative stress in plant sprouts via in vivo NIR-Ⅱ fluorescent imaging.In CT-XA-H_(2)O_(2),cyano-thiazole acts as the electron-accepting moiety and xanthane-aminodiphenyl as the electron-donating moiety,and dioxaborolane as the biomarker-responsive unit and fluorescence quencher.The probe CT-XA-H_(2)O_(2) shows weak fluorescent emission.When H_(2)O_(2) is present,the dioxaborolane in the probe is cleaved,consequently,the dye CT-XA-OH is generated and brings about significant fluorescent signals for detecting and imaging the in-situ biomarker.Moreover,the aminodiphenyl group endues the chromophore(the activated probe)with aggregation-induced emission characteristics,which ensures stronger fluorescence in the aggregated state in the aqueous milieu.The probe CT-XA-H_(2)O_(2) has been employed in the Cd^(2+)-ion or high-level salt(NaCl)induced oxidative stress models of soybean sprouts and peanut sprouts,and the experimental results evidently reveal the probe’s ability for in-situ biomarker-activatable in-vivo detection and imaging in the plants’sprouts.

Near-infrared fluorophores with absolute aggregation-caused quenching and negligible fluorescence re-illumination for in vivo bioimaging of nanocarriers

Environment-responsive fluorophores with aggregation-caused quenching(ACQ)properties have been applied to track nanocarriers with reduced artefacts caused by unbound or free fluorophores but suffer from incomplete fluorescence quenching and significant re-illumination,which undermine bioimaging accuracy.Herein,through structural modifications to reinforce the hydrophobicity,planarity and rigidity of fluorophores with an aza-BODIPY framework,probes featuring absolute ACQ(aACQ)and negligible re-illumination are developed and evaluated in various nanocarriers.aACQ probes,FD-B21 and FD-C7,exhibit near-infrared emission,high quantum yield,photostability,water sensitivity,and negligible re-illumination in blood,plasma and 1%Tween-80 in contrast to ACQ probe P2 and conventional probe DiR.All nanocarriers can be labeled efficiently by the tested fluorophores.Polymeric micelles(PMs)labeled by different aACQ probes manifest similar biodistribution patterns,which however differ from that of DiR-labeled PMs and could be ascribed to the appreciable re-illumination of DiR.Significantly lower re-illumination is also found in aACQ probes(2%-3%)than DiR(20%-40%)in Caco-2,Hela,and Raw264.7 cells.Molecular dynamics simulations unravel the molecular mechanisms behind aggregation and re-illumination,supporting the hypothesis of planarity dependency.It is concluded that aACQ fluorophores demonstrate excellent water sensitivity and negligible fluorescence re-illumination,making themselves useful tools for more accurate bioimaging of nanocarriers.