Crosslinked Hyaluronic Acid with Liposomes and Crocin Confers Cytoprotection in an Experimental Model of Dry Eye

Dry eye disease (DED) is a multifactorial condition caused by tear deficiency and accompanied by ocular surface damage. Recent data support a key role of oxidative and inflammatory processes in the pathogenesis of DED. Hyaluronic acid (HA) is widely used in artificial tears to treat DED by improving ocular hydration and reducing surface friction. Crocin (Cr), the main constituent of saffron, is a renowned compound that exhibits potent antioxidant and anti-inflammatory effects. The present study was undertaken to assess the viscosity and muco-adhesiveness of a photoactivated formulation with crosslinked HA (cHA), Cr, and liposomes (cHA-Cr-L). Our aim was also to evaluate whether cHA-Cr-L may exert cytoprotective effects against oxidative and inflammatory processes in human corneal epithelial cells (HCECs). Viscosity was measured using a rotational rheometer, and then the muco-adhesiveness was evaluated. Under hyperosmolarity (450 mOsm), the HCECs were treated with cHA-Cr-L. Interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα) were quantified by quantitative real-time polymerase chain reaction (RT-qPCR). The levels of reactive oxygen species (ROS) were measured using the DCF assay. The combined action of cHA-Cr-L produced a higher viscosity and muco-adhesiveness compared to the control. The anti-inflammatory effect of cHA-Cr-L was achieved through a significant reduction of IL-1β and TNFα (p < 0.001). The results also showed that cHA-Cr-L reduces ROS production under conditions of hyperosmolarity (p < 0.001). We conclude that cHA-Cr-L has potential as a therapeutic agent in DED, which should be further investigated.     

A novel copper(Ⅱ) complex-based fluorescence probe for nitric oxide detecting and imaging

A novel copper(II) complex CuQNE with a naphthalimide-containing ligand was synthesized as a fluorescent sensor of nitric oxide (NO). It featured eightfold fluorescent enhancement toward NO from a dark-background with the detection limit of NO about 1 nM in aqueous solution. The fluorescence response of the CuQNE was specific for NO, the presence of other reactive oxygen species (ROS) and reactive nitrogen species (RNS) did not interfere with the detection of NO in aqueous solution. LC–MS and IR spectra of the reaction mixture both demonstrated that the fluorescence enhancement was possibly attributed to an NO-induced nitrosation of the amino group. Confocal fluorescence images of MCF-7 cells suggested that CuQNE could be applied for monitoring intracellular NO.     

A fluorescent probe for copper and hypochlorite based on rhodamine hydrazide framework

A rhodamine derivative (1) was synthesized as a fluorescence turn-on probe for copper (Cu²⁺) and hypochlorite (ClO^?). The probe gave a fluorescence turn-on change at 587 nm with a color change from colorless to pink in the presence of Cu²⁺ or ClO^? ions in aqueous solution. It was found that the Cu²⁺ ion bound to 1 in a 1:1 stoichiometry and induced a spirolactam ring opening of the rhodamine moiety leading to a fluorescence turn-on, confirmed by Job’s plot, ESI-Mass, and ¹H NMR analyses. In the presence of ClO^? ion, probe 1 underwent a hypochlorite-mediated oxidation and hydrolysis to produce a ring-opened rhodamine B with a fluorescence enhancement. However, these changes were not monitored in case of other metal ions, anions, and reactive redox species. In addition, probe 1 can readily react with the ClO^? to provide a distinct fluorescence enhancement along with a pink color even in the presence of various competitive species.     

A fluorescent hydrogen peroxide probe based on a ‘click’ modified coumarin fluorophore

Herein a water-soluble ‘click’ modified coumarin-based fluorescent probe for hydrogen peroxide is reported. This probe shows significant intensity increases (up to fivefold) in near-green fluorescence upon reaction with hydrogen peroxide, and good selectivity over other reactive oxygen species.     

A highly sensitive fluorescence probe for thiophenol in living cells via a substitution-cyclization strategy

A novel fluorescent probe 1 was synthesized for the detection of thiophenol on the basis of a unique thiophenol-mediated substitution-cyclization reaction. The probe 1 displayed 420-fold fluorescence intensity enhancement and highly selective and sensitive response for thiophenol over other competing sulfur species. This probe showed an excellent linear relationship in 10–140 μM and the low detection limit of 29 nM. The recognition mechanism of probe 1 toward PhSH was supported by the NMR spectrum and ESI-MS. Furthermore, the probe 1 was successfully applied for detection of thiophenol in living HepG2 cells.     

A Highly Selective and Sensitive Ratiometric Fluorescent Probe for Hypochlorite and Its Application

A novel water-soluble hybrid fluorescein-coumarin dye(FLNC) fluorescence ratiometric probe to recognize OCl^- was designed and synthesized. The most prominent feature of the probe is that the molecular structure contains two different fluorophores, and the fluorescein moiety was connected to coumarin moiety by diacylhydrazine linker. When OCl^- was added, the two fluorophores in the FLNC probe could have a rapid respond simultaneously, with high selectivity and sensitivity towards OCl^- among other reactive oxygen species/reactive nitrogen species(ROS/RNS) and anions, and the detection limit was measured to be 0.30 μmol/L. In addition, the color changes of the solution could be observed by the naked eye and have a short response time(completed within 1 min), which suggestes that the probe FLNC has the potential to be used for real-time detection.     

Design of a novel mitochondria targetable turn-on fluorescence probe for hydrogen peroxide and its two-photon bioimaging applications

Considering that hydrogen peroxide (H₂O₂) plays significant roles in oxidative stress, the cellular signal transduction and essential biological process regulation, the detection and imaging of H₂O₂ in living systems undertakes critical responsibility. Herein, we have developed a novel two-photon fluorescence turn on probe, named as Pyp-B for mitochondria H₂O₂ detection in living systems. Selectivity studies show that probe Pyp-B exhibit highly sensitive response toward H₂O₂ than other reactive oxygen species (ROS) and reactive nitrogen species (RNS) as well as biologically relevant species. The fluorescence colocalization studies demonstrate that the probe can localize in the mitochondria solely. Furthermore, as a bio-compatibility molecule, the highly selective and sensitive of fluorescence probe Pyp-B have been confirmed by its cell imaging application of H₂O₂ in living A549 cells and zebrafishes under the physiological conditions.     

A pinacol boronate caged NIAD-4 derivative as a near-infrared fluorescent probe for fast and selective detection of hypochlorous acid

A pinacol boronate caged NIAD-4 derivative was demonstrated to be a near-infrared fluorescent probe for fast and selective detection of hypochlorite over other ROS species.     

Design of a novel mitochondria targetable turn-on fluorescence probe for hydrogen peroxide and its two-photon bioimaging applications

Considering that hydrogen peroxide (H₂O₂) plays significant roles in oxidative stress, the cellular signal transduction and essential biological process regulation, the detection and imaging of H₂O₂ in living systems undertakes critical responsibility. Herein, we have developed a novel two-photon fluorescence turn on probe, named as Pyp-B for mitochondria H₂O₂ detection in living systems. Selectivity studies show that probe Pyp-B exhibit highly sensitive response toward H₂O₂ than other reactive oxygen species (ROS) and reactive nitrogen species (RNS) as well as biologically relevant species. The fluorescence colocalization studies demonstrate that the probe can localize in the mitochondria solely. Furthermore, as a bio-compatibility molecule, the highly selective and sensitive of fluorescence probe Pyp-B have been confirmed by its cell imaging application of H₂O₂ in living A549 cells and zebrafishes under the physiological conditions.     

A 4-aminonaphthalimide based environmentally sensitive fluorescence probe

A simply synthesized 4-aminonaphthalimide derivative 1 expresses both polarity and viscosity sensitive fluorescence spectra, indicating its potential usage as an environmentally sensitive fluorescence probe. By comparing the fluorescence behavior of 1 with that of a known 4-aminonaphthalimide derivative 2, it was found that the substitution of the 4-amino group has profound influence on the environmentally sensitive fluorescence properties of 4-aminonaphthalimide.     

A TPA-caged precursor of (imino)coumarin for “turn-on” fluorogenic detection of Cu

We strategize to utilize the precursors of (imino)coumarin fluorophores to deliver novel reactive Cu⁺ probes, where tris[(2-pyridyl)-methyl] amine (TPA) works as a reactive receptor towards Cu⁺. To verify this strategy, CP1, a representative probe and relevant sensing behaviors towards Cu⁺ are presented here. CP1 features good solubility and fast response for monitoring labile copper in aqueous solution and live cells. The sensing mechanism of CP1 is determined by HPLC titration and mass spectrometric analysis. The probe CP1 exhibits a 60-fold fluorescence enhancement and a detection limitation of 10.8 nM upon the detection of Cu⁺. CP1 is further applied for imaging labile copper in live cells. This work provides a starting point for future development of Cu⁺ probes, based on in situ formation of (imino)coumarin scaffolds, as well as their further investigations of copper signaling and biological events.     

A far-red fluorescent probe for selective G-quadruplex DNA targeting

The development of rapid and simple approaches for detection of G-quadruplex DNA structures has attracted significant attention to disclose their diverse physiological and pathological functions. Thiazole orange (TO) is a common fluorescence probe used for the detection of G-quadruplexes. However, it still suffers from some common problems like non-selective for G-quadruplex and emission in the lower wavelength region of spectrum, thus hampering its further applications. Probes with turn-on fluorescence in the far-red region are highly sought-after due to minimal auto-fluorescence and cellular damage. In this paper, we described a far-red fluorescent probe (L-1) by introducing an amine group into styrylquinolinium scaffold. The experimental results indicated that L-1 exhibited significant fluorescence enhancement when treated with G-quadruplexes but retained weak fluorescence in the presence of duplex DNAs. In addition, this probe also displayed higher binding affinity for parallel G-quadruplexes. The characteristics of L-1 were further investigated with UV–vis spectrophotometry, fluorescence, circular dichroism, KI quenching, FID assay and molecular docking to validate optical photophysical properties, as well as the selectivity, sensitivity and detailed binding mode toward G-quadruplex DNAs.     

Synthesis of 2′-deoxycytidine and its triphosphate bearing tryptophan-based imidazolinone fluorophore for environment sensitive fluorescent labelling of DNA

We synthesized 2′-deoxycytidine and the corresponding nucleoside triphosphate bearing (indol-3-yl)methylene-2-methyl-5-oxo-4,5-dihydroimidazol-1-yl group (a tryptophan-based fluorophore from cyan fluorescent protein) linked through a propargyl group at position 5. The fluorophore is weakly solvatochromic, sensitive to pH, and, as a molecular rotor, it is highly sensitive to viscosity. In low viscosity solvents, the fluorescence is very weak, whereas in more viscous environment it lights up. Primer extension or PCR using the modified dC^TrpTP and KOD XL DNA polymerase was used for construction of labelled oligonucleotides and DNA. Preliminary study showed a 2-fold increase of fluorescence of labelled ON probe in presence of single strand-binding protein indicating a potential of this label for sensing of protein-DNA interactions.     

GSH responsive traditional clinical drugs probe for cancer cell fluorescence imaging and therapy

Despite the rapid development of fluorescence detection modalities for disease diagnosis, novel fluorescent molecules and probes still face with tremendous pressure to transform before employing such fluorescent tools in the clinic. Impressively, the fluorescent probes based on the traditional fluorescent dye are expected to accelerate the transformation process. Herein, methylene blue is requisitioned to design the GSH responsive probe MB-SS-CPT elaborately. The as-synthesized MB-SS-CPT provides a dramatic optical advantage for GSH detection in vitro, cell fluorescence imaging, in vivo imaging, and antitumor therapy.     

A mitochondria-targeted fluorescent probe for ratiometric detection of hypochlorite in living cells

A new fl uorescent probe 1 was designed for mitochondrial localization and ratiometric detection of hypochlorite in living cells. It is noteworthy that a high Pearson’s co-localization coeffi cient (Rr) we have obtained was calculated to be 0.97.     

Toward a highly sensitive and selective indole-rhodamine-based light-up probe for Hg2+ and its application in living cells

We herein designed and synthesized a light-up fluorescent probe L1 for Hg²⁺ species, which is based on indole derivative and Rhodamine fluorophore. The new probe can show a linear response to Hg²⁺ with high sensitivity and selectivity. As the Hg²⁺ concentration changed from 0 to 450 μM, the fluorescence intensity of L1 at 575 nm changed from 50 to 6181 (～120-fold). The detection limit of the probe was 5.0 × 10^?8 M. Besides, we have successfully applied L1 to monitor Hg²⁺ species in living MCF-7 cells by way of fluorescence imaging.     

Assessment of Murine Colon Inflammation Using Intraluminal Fluorescence Lifetime Imaging

Inflammatory bowel disease (IBD) is typically diagnosed by exclusion years after its onset. Current diagnostic methods are indirect, destructive, or target overt disease. Screening strategies that can detect low-grade inflammation in the colon would improve patient prognosis and alleviate associated healthcare costs. Here, we test the feasibility of fluorescence lifetime imaging (FLIm) to detect inflammation from thick tissue in a non-destructive and label-free approach based on tissue autofluorescence. A pulse sampling FLIm instrument with 355 nm excitation was coupled to a rotating side-viewing endoscopic probe for high speed (10 mm/s) intraluminal imaging of the entire mucosal surface (50–80 mm) of freshly excised mice colons. Current results demonstrate that tissue autofluorescence lifetime was sensitive to the colon anatomy and the colonocyte layer. Moreover, mice under DSS-induced colitis and 5-ASA treatments showed changes in lifetime values that were qualitatively related to inflammatory markers consistent with alterations in epithelial bioenergetics (switch between β-oxidation and aerobic glycolysis) and physical structure (colon length). This study demonstrates the ability of intraluminal FLIm to image mucosal lifetime changes in response to inflammatory treatments and supports the development of FLIm as an in vivo imaging technique for monitoring the onset, progression, and treatment of inflammatory diseases.     

A boronate-based ratiometric fluorescent probe for fast selective detection of peroxynitrite

Given that peroxynitrite (ONOO^?) is profoundly associated with health and diseases, a new fluorescent probe ABT was designed and synthesized for detection of ONOO^?. ABT manifested not only ratiometric fluorescence signals simultaneously in response to concentrations of ONOO^? (within 10?s), but high selectivity and sensitivity towards ONOO^? over other physiological relevant species (detection limit?=?26.3?nM). Moreover, ABT worked in a broad pH range with biological relevance. Thus, ABT could be used to quantitative detection of ONOO^? concentration and has the potential to efficiently monitor ONOO^? in living organisms.     

A multi-responsive diarylethene-rhodamine 6G derivative for sequential detection of Cr3+ and CO32−

A new unsymmetrical diarylethene derivative (1o) with rhodamine 6G as a functional group has been designed and synthesized. It displayed good physicochemical properties induced by lights and chemical stimuli. 1o could sensitively detect towards Cr³⁺ with a 1:1 stoichiometry, and exhibit an obviously fluorescence (from dark to light cyan) and color (from colorless to pink) changes during the recognition process. The limit of detection was determined to be 27?nM and 8.5?nM via UV/vis and fluorescence methods, respectively. More importantly, the resulting complex 1o-Cr³⁺ (1o') could be served as a potential fluorescent probe to selectively and sensitively recognize toward CO₃^2?, the limit of detection was determined to be 0.88?μM and 0.26?μM via UV/vis and fluorescence methods, respectively. Moreover, the quenching of fluorescence intensity can reach 95% due to the perfect FRET processes between the excited open-ring rhodamine 6G moiety and the closed-ring diarylethene unit.     

A novel ratiometric fluorescent probe based on coumarin derivative for the recognition of Al(III) and its application on test strips

A novel ratiometric probe (L) which was composed of chromone and coumarin moieties has been designed and synthesized for sensing Al³⁺ in EtOH in view of the internal charge transfer (ICT) mechanism. The free probe L exhibited a strong fluorescence emission at 477 nm, and the fluorescence emission here almost disappeared after adding Al³⁺ (10 equiv.) while a new peak appeared at 524 nm. This may be due to the enhancement of intramolecular electron transfer efficiency from donor to acceptor. In addition, this probe L could be form a 1:1 complex with Al³⁺, which could be explained by the ESI-MS spectra, and L had a low detection limit for Al³⁺ with a binding constant of 1.32 × 10⁴ M⁻¹. More importantly, L could be applied to a solid probe for rapid detection of Al³⁺ with a significant color change.