Hemicyanine Dye Research Articles

Viscosity probes towards different organelles with red emission based on an identical hemicyanine structure.

A series of viscosity probes targeting different organelles were obtained using a single hemicyanine dye as the matrix structure. Specifically, probes 1a-d were obtained by introducing four amines (6-amino-2H-chromen-2-one, N-(2-aminoethyl)-4-methylbenzenesulfonamide, dodecan-1-amine and N,N diphenylbenzene-1,4-diamine) into the indole hemicyanine dye of the carboxylic acid with a D-π-A structure. Their maximum absorption wavelengths were in the range 570-586 nm and they had relatively large molar absorption coefficients, while their maximum emission wavelengths in the red light region were in the range 596-611 nm. Moreover, their fluorescence intensity in glycerol was 35-184 times higher than that in phosphate buffer solution (PBS). The lg(Fl) and lg η of probes 1a-d showed good linearity with high correlation coefficients according to the Förster-Hoffman equation. In addition, cell staining experiments demonstrated that 1a-c could target lysosomes, endoplasmic reticulum and mitochondria, respectively. They could also undergo viscosity-detectable changes in the corresponding organelles under the action of the corresponding ion carriers.

Spectroscopic investigation of energy transfer from composition dependent ternary QDs to hemicyanine dye

Systematic spectroscopic investigation of fluorescence (Förster) resonance energy transfer (FRET) is performed for a pair of ternary quantum dots (TQDs) CdSeS/ZnS with LDS698 dye. Composition of TQDs plays an important role in tuning emission wavelength keeping the size same. Coupling of-COOH functionalized QDs with dye results in decreasing fluorescence intensity and lifetimes of QDs analogous to quenching mechanism. The observed enhancement in acceptor intensity is essentially due to dipole–dipole interaction confirming energy transfer and its dependence on spectral overlap. FRET parameters like spectral overlap, Förster’s distance, intermolecular distance, etc., are calculated. The results strongly suggest that the chosen FRET pairs find potential application in bio-imaging and targeted drug delivery.

Single-atom engineering of hemicyanine and its amphiphilic derivative for optimized near infrared phototheranostics.

Near-infrared (NIR) dyes are widely used in the field of in vivo phototheranostics. Hemicyanine dyes (HDs) have recently received tremendous attention due to their easy synthesis and excellent NIR features. However, HDs can easily form non-fluorescent aggregates and their potential for phototherapy still needs further exploration due to their poor ability to generate reactive oxygen species (ROS). Herein, a series of hemicyanine dyes with different chalcogen atom (O, S, Se) substitutions were constructed to achieve optimized potential for phototheranostics. By replacing O with the heavy atom Se in the xanthene skeleton, CySe-NEt2 showed much more favourable features such as extended NIR absorption/emission wavelength, boosted 1O2 generation rate and higher photothermal effect. In addition, a poly(ethylene glycol) (PEG) group was introduced into the scaffold and yielded a nanotheranostic agent CySe-mPEG5K, which easily formed nanoparticles with appealing features such as excellent photostability, effective prevention of unpleasant H-aggregation, fast/selective tumor accumulation and minimum dark toxicity. Solid tumor growth was significantly suppressed through combined photodynamic therapy (PDT) and photothermal therapy (PTT) guided by NIR fluorescence (NIRF) and photoacoustic (PA) imaging. This study not only presents the first example of selenium-substituted hemicyanine dyes, but also offers a reliable design strategy for the development of potent NIR phototheranostic agents with multi-mode imaging-guided combination therapeutic ability.

Construction of layer-by-layer self-assembly coatings based on hemicyanine derivative for photodynamic antimicrobial application

Two-component composite films containing hemicyanine (C3) and indigo carmine (IC) dye were prepared via layer-by-layer self-assembly. The positively charged C3 has a conjugate backbone and hydrophilic groups, which could capture negatively charged bacteria on the surface of substrate by electrostatic and hydrophobic interactions. In addition, the donor-receptor structure of C3 also promotes intramolecular charge transfer to boost the generation of reactive oxygen species (ROS) for antibacterial therapy. Under the irradiation of white light, the three-layer film can display prominent photodynamic antibacterial activity, and the inhibition efficiency against the ampicillin resistant (Ampr) E. coli strain is as high as 90% with killing 3.6 × 108 of E. coli cells per cm2.

Multiple Effects of an Anionic Cyclodextrin Macrocycle on the Reversible Isomerization of a Photoactive Guest Dye.

Understanding and controlling the reversible isomerization of photoactive molecules in order to obtain a tunable optical response is desirable for many photofunctional applications. This study describes the interesting effects of an anionic cyclodextrin host (sulfated-βCD, SCD) on the photoisomerization and protonation equilibrium of an important hemicyanine dye (trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide, DSP). The SCD host assists in unlocking the photoisomerization potential of DSP by promoting protonation of the dye. It also assists in stabilizing the cis isomer of the protonated dye, thereby significantly delaying the reverse cis to trans isomerization of DSPH+. Furthermore, the interplay of both hydrophobic and electrostatic interactions in the complex formation of SCD with DSPH+ makes the reverse cis to trans isomerization of DSPH+ amenable to influence by the added salt. The stimuli-responsive reversible isomerization of SCD-DSPH+ is an interesting case from the perspective of chemical sensing or light operated functional materials with host-guest systems.

Tuning the DNA binding properties of phenolic hemicyanine dyes for host-guest fluorescent aptasensor applications

Fluorescent dyes that bind specifically to DNA aptamers with turn-on emission serve as powerful tools for biosensor development. DNA three-way junctions (3WJs) consisting of a Y-shaped hydrophobic branch point connecting three double-stranded stems serve as recognition elements for DNA aptasensors for a wide variety of diagnostic applications. Herein, we highlight the tunability of phenolic hemicyanine dyes for host-guest fluorescent aptasensor applications using the cocaine-binding aptamer (MN4) as a representative 3WJ-aptamer substrate. The DNA aptamer MN4 exhibits ligand binding promiscuity and binds the alkaloid quinine with ∼26-fold greater affinity than its intended cocaine target. Combining the cationic N-methylbenzothiazolium (Btz) acceptor with a 2-fluoro-phenolic (FPhO) donor through a vinyl-linkage creates the FPhOBtz hemicyanine as a universal fluorescent turn-on probe for DNA 3WJs. The FPhOBtz dye binds MN4 with higher affinity than cocaine, but with weaker affinity than quinine. Consequently, FPhOBtz displacement from the 3WJ with turn-off fluorescence is effectively mediated by quinine, but not cocaine, resulting in poor detection of cocaine by the dye-displacement assay. Our current results demonstrate superior cocaine detection by replacing the planar cationic Btz group with the non-planar indolenium (Ind) acceptor to afford FPhOInd as the signaling fluorescent probe. This simple change in dye structure strongly diminishes MN4 binding affinity (19-fold) with cocaine now possessing stronger affinity for the 3WJ of MN4 compared to FPhOInd. Consequently, FPhOInd displacement from MN4 is effectively mediated by cocaine to provide a 13-fold improvement in cocaine detection in undiluted urine using the host-guest biosensing platform.

Activity-Based Fluorescent Probes Based on Hemicyanine for Biomedical Sensing.

In recent years, fluorescent probes, as an analytical tool that can target and rapidly detect analytes, have been increasingly used for applications related to medical treatment, detection, and bioimaging. Researchers are interested in hemicyanine-based fluorescent probes because of their high quantum yield, tunable spectrum characteristics, absorption and emission in the near-infrared (NIR) region, and good photo-stability. The development of these dyes and their derivatives as NIR fluorescent probes for biological applications has advanced significantly in the last ten years. This review introduces processes for making hemicyanine dyes and the methodology for creating functional activity-based fluorescent probes. A variety of hemicyanine-based probes have been systematically developed for the detection of small biomolecules in various illnesses. Finally, the potential drawbacks of hemicyanine-based functional probes, and the prospects for future research and translation into clinical medicine, are also discussed. This study is intended to provide strategies for the development and design of novel fluorescence probes.

Three Birds with One Stone: Acceptor Engineering of Hemicyanine Dye with NIR-II Emission for Synergistic Photodynamic and Photothermal Anticancer Therapy.

It is challenging to develop a near-infrared (NIR) small molecular photosensitizer for synergistic phototherapy in deep tissues. Herein, first, a heavy-atom-free NIR hemicyanine photosensitizer (BHcy) for 808nm light-mediated synergistic photodynamic therapy/photothermal therapy (PDT/PTT) anticancer therapy by leveraging the acceptor engineering strategy is reported. This strategy endows BHcy with a more planar and larger π-conjugated structure, resulting in long NIR absorption/emission at 770/915-1200nm as well as enhanced singlet oxygen (1 O2 ) generation ability and photothermal effect, which is ascribed to the reduced energy levels of excited singlet/triplet states and the promoted intersystem crossing process. Notably, BHcy-based nanoparticles (BHcy-NPs) exhibit efficient 1 O2 yield (12.9%) and high photothermal conversion efficiency (55.1%). More importantly, BHcy-NPs are able to significantly kill cancer cells by destroying main organelles and inhibit tumor growth in vivo after a single irradiation. Overall, this study provides a strategy to design new heavy-atom-free PDT/PTT agents for potential clinical applications.

Linear and nonlinear absorption properties of hemicyanine dyes containing 5-(4H)-oxazolone as heterocyclic ring

A series of dyes containing electron-donating (D) and electron-accepting (A) groups connected through a π-conjugated linker were designed and their linear and nonlinear absorption properties were studied. The dyes combined 1,3-oxazol-5(4H)-one core with methoxy, methyl, phenyl, cyano, and nitro group in the para-position of a phenyl ring. Spectrally resolved two-photon absorption cross-section measurements carried out by the femtosecond Z-scan technique showed wide wavelength regions of nonlinear optical absorption. The studied compound containing the phenyl ring exhibits relatively high effective two-photon absorption cross-section equal to 772 ± 100 GM at 600 nm. The experimental optical characterization is supported by the results of electronic-structure calculations.

A near-infrared emitted fluorescence probe for the detection of biosulfite in live zebrafish, mouse and real food samples.

Bisulfite (HSO3-) has been widely used as an important food additive in daily life. Furthermore, a normal amount of HSO3- plays a significant role in biological systems. However, excessive intake of HSO3- will lead to a variety of diseases. Therefore, it is of great significance to develop an efficient fluorescent probe that can be used for detection of HSO3- in biological systems and food samples. In this work, a near-infrared (NIR) emitted fluorescent probe (SZY) based on hemicyanine dye was successfully synthesized and applied to detect HSO3- in several food samples and live animals. The proposed nucleophilic addition sensing mechanism of SZY towards HSO3- has been confirmed by 1H NMR titration, high resolution mass spectrometry (HR-MS) and density functional theory (DFT) theoretical computation. The HSO3--induced nucleophilic reaction with α,β-unsaturated CC binding of SZY results in the dramatic decline of the UV-vis absorption and remarkable quenching of the fluorescence emission. SZY features the advantages of near infrared emission (centered at 720nm), high water solubility (in 98% aqueous solution), fast response time (50s), large Stokes shift (244nm) and low cytotoxicity. The probe SZY was successfully applied to image of HSO3- in live nude mouse and adult zebrafish. Semi-quantitatively analyzing the HSO3- level by "naked eye" in several food samples including canned fruit, white wine, white sugar and jasmine tea drinks has been realized by the colorimetric method.

The Unexpected Selectivity Switching from Mitochondria to Lysosome in a D-π-A Cyanine Dye.

Two interesting benzothizolium-based D-π-A type hemicyanine dyes (3a–3b) with a diphenylamine (-NPh2) donor group were evaluated for fluorescence confocal microscopy imaging ability in live cells (MO3.13, NHLF). In sharp contrast to previously reported D-π-A dyes with alkyl amine donor (-NR2) groups (1), 3a and 3b exhibited significantly different photophysical properties and organelle selectivity. Probes 3a and 3b were nearly non-fluorescent in many polar and non-polar solvents but exhibited a bright red fluorescence (λem ≈ 630–640 nm) in stained MO3.13 and NHLF with very low probe concentrations (i.e., 200 nM). Fluorescence confocal microscopy-based co-localization studies revealed excellent lysosome selectivity from the probes 3a–3b, which is in sharp contrast to previously reported D-π-A type benzothiazolium dyes (1) with an alkyl amine donor group (-NR2) (exhibiting selectivity towards cellular mitochondria). The photostability of probe 3 was found to be dependent on the substituent (R’) attached to the quaternary nitrogen atom in the cyanine dye structure. The observed donor-dependent selectivity switching phenomenon can be highly useful in designing novel organelle-targeted fluorescent probes for live-cell imaging applications.

A novel fluorescent probe for imagining hydrogen sulfide upregulation in acute lung injury

Acute lung injury (ALI) is a severe pulmonary inflammatory disease with high morbidity and mortality, whose pathogenesis and treatment are still under exploration. Hydrogen sulfide (H2S), a member of gas signal molecules and a biomarker for a variety of diseases, is known to be closely related to ALI. However, the dynamic change of H2S levels in this pathological process is still unclear. Herein, a novel fluorescent probe HCy-HSP based on a sulfur-substitution hemicyanine dye was constructed through a facile routine. The probe exhibited an enhanced near-infrared emission compared to the traditional hemicyanine probes and a rapid and significant "turn-on" fluorescence response to H2S. The fluorescence imaging of endogenous H2S under different stimulation conditions in normal/cancer cells has been realized by using HCy-HSP. Furthermore, HCy-HSP has been successfully applied to the visualization of H2S levels in ALI mice via in vivo /organ near-infrared fluorescence imaging for the first time. The probe could be a promising molecular tool for exploring the physiological role of H2S in pulmonary diseases and other pathological activities.

A hemicyanine-based fluorescent probe for simultaneous imaging of Carboxylesterases and Histone deacetylases in hepatocellular carcinoma

Carboxylesterases (CESs) and Histone deacetylases (HDACs) are regarded as important signaling enzymes highly associated with the development and progression of multiple cancers, including hepatocellular carcinoma (HCC). In this work, a near-infrared (NIR) fluorescent probe named Lys-HXPI was designed and synthesized, which linked a hemicyanine dye and 6-acetamidohexanoic acid via an ester bond. Lys-HXPI displayed a remarkable increase with a NIR emission at 720 nm, a low detection limit (<10 nM) for HDAC1, HDAC 6, CES1 and CES2, as well as a high selectivity for the target enzymes over other relevant analytes. Furthermore, Lys-HXPI was used to image endogenous target enzymes in living cells, tumor-bearing nude mice and tissue slices. The ability of Lys-HXPI to simultaneous image CESs and HDACs was demonstrated with RT-qPCR and the confocal imaging in Hep G2 and MDA-MB-231. Taking advantage of NIR emission, the probe was also successfully applied to imaging Hep G2 tumor mice and tissue slices. Lys-HXPI is expected to be useful for the effective detecting of CESs and HDACs in complex biosystems.

Activatable Fluorescent-Photoacoustic Integrated Probes with Deep Tissue Penetration for Pathological Diagnosis and Therapeutic Evaluation of Acute Inflammation in Mice.

Inflammation is associated with many diseases, so the development of an excellent near infrared fluorescent (NIRF) and photoacoustic (PA) dual-modality probe is crucial for the accurate diagnosis and efficacy evaluation of inflammation. However, most of the current NIRF/PA scaffolds are based on repurposing existing fluorescent dye platforms that exhibit non-optimal properties for both NIRF and PA signal outputs. Herein, we developed a novel dye scaffold QL-OH by optimizing the NIRF and PA signal of classical hemicyanine dyes. Based on this optimized dye, we developed the first NIRF/PA dual-mode carbon monoxide (CO) probe QL-CO for noninvasive and sensitive visualization of CO levels in deep inflammatory lesions in vivo. The novel probe QL-CO exhibited rapid and sensitive NIRF775/PA730 dual activation responses toward CO. In addition, the CO-activated probe QL-CO was successfully used for the diagnosis of inflammation and evaluation of anti-inflammation drug efficacy in living mice though the NIRF/PA dual-mode imaging technology for the first time. More importantly, the probe QL-CO could accurately locate the deep inflammatory lesion tissues (≈1 cm) in mice and obtain 3D PA diagnostic images with deep penetration depth and spatial resolution. Therefore, the new NIRF/PA dual-mode probe QL-CO has high potential for deep-tissue diagnosis imaging of CO in vivo. These findings may provide a new tool and approach for future research and diagnosis of CO-associated diseases.

A hemicyanine-based near-infrared fluorescent probe for vapor-phase hydrazine detection and bioimaging in a complete aqueous media

A novel near-infrared fluorescent probe CyOE based on hemicyanine dye containing acetyl as a recognition site is reported. The probe CyOE shows high selectivity and sensitivity (LOD = 82 nM, 2.58 ppb), as well as good water solubility and quantitative detectability of hydrazine in the concentration range of 0–75 μM (R2 = 0.993). Moreover, CyOE has a significant increase in fluorescence at 735 nm with the addition of N2H4, which provides a rapid, colorimetric and gas-phase detection method for N2H4 in both aqueous solution and real water samples. In addition, CyOE is successfully utilized to visualize hydrazine in cells with low cytotoxicity and high cell permeability.

Benzoselenazolium-based hemicyanine dye for G-Quadruplex detection

Benzothiazolium and benzoxazolium are common groups for the construction of hemicyanine dyes; however, their isosteric analogue benzoselenazolium have rarely been studied. Here, we report the development of the first benzoselenazolium-based hemicyanine dye for the selective detection of G-quadruplexes. This molecule, SEMA-1, was validated as a red-emitting and activatable fluorescent probe whose fluorescence would only be activated in the presence of G-quadruplexes in buffer solution. Consistent with this, SEMA-1 was found to accumulate in nucleoli and could be used to detect the high abundance of nucleolar rDNA and rRNA G-quadruplexes in fixed HeLa cells. On the other hand, due to the retained mitochondrial membrane potential in live HeLa cells, SEMA-1 was captured by mitochondria and had the potential to detect the mitochondrial G-quadruplexes. Collectively, this work demonstrates the value of developing G-quadruplex-specific fluorescent probes from novel benzoselenazolium-based hemicyanine scaffold.

An isothiocyanate-functionalized self-immolative near-infrared fluorescence probe for cysteine sensing and bioimaging in living systems

Biothiols play vital roles in human pathophysiology, with cysteine (Cys) a promising clinical biomarker for many diseases. Therefore, new tools to sensitively and specifically monitor Cys under physiological conditions and in living systems are urgently required. Consisting of a hemicyanine dye and isothiocyanate as the recognition group and self-immolative trigger, here we constructed a near-infrared (NIR) fluorescence probe named CyOH-NCS to specifically sense Cys. The hydroxyl-protected molecule maintained inactive fluorescence until specific attack of the isothiocyanate group by Cys to induce self-immolation and release of the native fluorophore as a NIR fluorescence output. Moreover, the CyOH-NCS probe was used to successfully visualize Cys in living cells, zebrafish and mice. Finally, hydrogen sulfide (H2S) release experiments demonstrated that the CyOH-NCS probe was a responsive H2S donor, indicating potential dual use in pathophysiological applications.

An Activatable Polymeric Nanoprobe for Fluorescence and Photoacoustic Imaging of Tumor-Associated Neutrophils in Cancer Immunotherapy.

Imaging to evaluate tumor-associated neutrophils (TANs) is imperative for cancer immunotherapy but remains challenging. We herein report an activatable semiconducting polymer nanoprobe (SPCy) for near-infrared fluorescence (NIRF) and photoacoustic (PA) imaging of neutrophil elastase (NE), a biomarker of TANs. SPCy comprises a semiconducting polymer conjugated with a hemicyanine (hemi-Cy) dye caged by a NE-cleavable peptide as the side chain. After systemic administration, SPCy passively targets the tumor and reacts with NE to "uncage" the hemi-Cy, leading to enhanced NIRF and PA signals of the hemi-Cy but unchanged signals of the SP. Such NE-activated ratiometric NIRF and enhanced PA signals of SPCy correlate with the intratumoral population of TANs. Thus, this study not only presents the first TAN-specific PA probe, but also provides a general molecular design strategy for PA imaging of other immune-related biomarkers to facilitate screening of cancer immunotherapeutics.

An Activatable Polymeric Nanoprobe for Fluorescence and Photoacoustic Imaging of Tumor‐Associated Neutrophils in Cancer Immunotherapy

AbstractImaging to evaluate tumor‐associated neutrophils (TANs) is imperative for cancer immunotherapy but remains challenging. We herein report an activatable semiconducting polymer nanoprobe (SPCy) for near‐infrared fluorescence (NIRF) and photoacoustic (PA) imaging of neutrophil elastase (NE), a biomarker of TANs. SPCy comprises a semiconducting polymer conjugated with a hemicyanine (hemi‐Cy) dye caged by a NE‐cleavable peptide as the side chain. After systemic administration, SPCy passively targets the tumor and reacts with NE to “uncage” the hemi‐Cy, leading to enhanced NIRF and PA signals of the hemi‐Cy but unchanged signals of the SP. Such NE‐activated ratiometric NIRF and enhanced PA signals of SPCy correlate with the intratumoral population of TANs. Thus, this study not only presents the first TAN‐specific PA probe, but also provides a general molecular design strategy for PA imaging of other immune‐related biomarkers to facilitate screening of cancer immunotherapeutics.

Stability and Self-Association of styryl hemicyanine dyes in water studied by 1H NMR spectroscopy

The stability in water of five styryl hemicyanine dyes containing benzoxazole, benzothiazole, benzoselenazole and oxazolopyridne rings with different substituents at different pH values has been investigated. All compounds are stable at acidic and neutral pH, however, at basic pH the oxazole dyes undergo a ring opening reaction. The stability at basic pH is increased by substituting the benzooxazolium with oxazolopyridium function in the oxazole dyes 3a and 3e. 1H and 1H DOSY solution NMR spectroscopy prove that slight structural changes result in significant differences in the process of self-association. The association constants for dimerization have been determined by curve fitting the concentration dependent 1H NMR spectra based on the isodesmic model. Van’t Hoff analysis has been used to determine the thermodynamic parameters of the self-association process. The aggregation in water decreases with decreasing electronegativity and increasing the charge delocalization in the row (E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]oxazol-3-ium iodide (3a), (E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]thiazol-3-ium iodide (3b), (E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[1,3-d]selenazol-3-ium iodide (3d) in the oxazole/thiazole/selenazole analogues. Introducing methyl groups in the benzothiazole ring enhances stacking effects in water due to stronger hydrophobic character. This derivative is characterized by the highest self-association constant (ka = 299 L mol−1) and the lowest Gibbs energy (ΔG = -14 kJ mol−1). Substituting the phenyl with pyridyl ring in the oxazole analogue enhances significantly the solubility in water and thus decreases the self-association constant. Concentration dependent 1H ROESY spectra provide information about the orientation of the molecules in the stack.