Fluorescent Probe For Selective Imaging Research Articles

Naphthalimide-based Functional Glycopolymeric Nanoparticles as Fluorescent Probes for Selective Imaging of Tumor Cells.

A series of functional glycopolymer nanoparticles with 1,8-naphthalimide motif was designed, synthesized and applied for tumor cell imaging. With the pH-sensitive and aggregation-induced emission (AIE) effect of the 1,8-naphthalimide fluorescent probe, the presence of glucose-based glycopolymers enhanced its water-solubility and biocompatibility. Owing to the dual tumor-targeting effects of the dense glucose part and the boronic ester modification, the obtained glycopolymers showed high affinity to tumor cells, with a much faster staining rate than normal cells, indicating a great potential for diagnosis and treatments of cancers.

Rational design synthesis and evaluation of a novel near-infrared fluorescent probe for selective imaging of amyloid-β aggregates in Alzheimer's disease

Alzheimer's disease (AD) is a degenerative neurological disorder that remains incurable to date, seriously affecting the quality of life and health of those affected. One of the key neuropathological hallmarks of AD is the formation of amyloid-β (Aβ) plaques. Near-infrared (NIR) probes that possess a large Stokes shift show great potential for imaging of Aβ plaques in vivo and in vitro. Herein, we proposed a rational strategy for design and synthesis of a series of NIR fluorescent probes that incorporate a tricarbonitrile group as a strong electron-withdrawing group (EWG) to enable NIR emission and large Stokes shift for optimal imaging of Aβ plaques. The probe TCM-UM exhibited remarkable in vitro performance, including strong NIR emission (λem = 670 nm), large Stokes shift (120–245 nm), and its affinity for Aβ42 aggregates (Kd = 43.78 ± 4.09 nM) was superior to the commercially available probe Thioflavin T (ThT, Kd = 896.04 ± 33.43 nM). Further, TCM-UM was selected for imaging Aβ plaques in brain tissue slices and APP/PS1 transgenic (AD) mice, the results indicated that TCM-UM had an excellent ability to penetrate the blood-brain barrier (BBB) compared with ThT, and it could effectively distinguish wild-type (Wt) mice and APP/PS1 transgenic (AD) mice.

A ratiometric fluorescent probe for selective imaging of methylglyoxal in living cells

Fluorescent imaging of methylglyoxal (MGO) is essential for understanding the role of MGO played in cellular processes and pathogenesis. However, the development of fluorescent MGO probes with accurate imaging capabilities remains a challenge. In this study, we designed and synthesized an isophorone-based ratiometric fluorescent MGO probe for ratiometric imaging of MGO in living cells. The probe shows highly selective and sensitive response to MGO over other biological species. Notably, ratiometric fluorescent imaging of MGO in living HeLa cells demonstrates the promising imaging ability of the probe for studying the biological roles of MGO played in living cells.

A Photoinduced Electron Transfer-Based Hypochlorite-Specific Fluorescent Probe for Selective Imaging of Proinflammatory M1 in a Rheumatoid Arthritis Model.

The differentiation of the distinct phenotypes of macrophages is essential for monitoring the stage of inflammatory diseases for accurate diagnosis and treatment. Recent studies revealed that the level of hypochlorite (OCl-) varies from activated M1 macrophages (killing pathogens) to M2 (resolution of inflammation) during inflammation. Thus, we developed a simple and efficient fluorescent probe for discriminating M1 from M0 and M2. Herein, fluorescent-based imaging is applied as an alternative to immunohistochemistry, which is challenging due to the tedious process and high cost. We developed a hypochlorite-specific probe PMS-T to differentiate M1 and M2, employing a metabolism-oriented live-cell distinction. This probe enables the detection of inflammatory rheumatoid arthritis in an ex vivo mouse model. Thus, it can be a potential chemical tool for monitoring inflammatory diseases, including rheumatoid arthritis, that may overcome the existing barriers of immunohistochemistry.

Rational design and synthesis of a novel BODIPY-based probe for selective imaging of tau tangles in human iPSC-derived cortical neurons

Numerous studies have shown a strong correlation between the number of neurofibrillary tangles of the tau protein and Alzheimer's disease progression, making the quantitative detection of tau very promising from a clinical point of view. However, the lack of highly reliable fluorescent probes for selective imaging of tau neurofibrillary tangles is a major challenge due to sharing similar β–sheet motifs with homologous Amyloid-β fibrils. In the current work, we describe the rational design and the in silico evaluation of a small-size focused library of fluorescent probes, consisting of a BODIPY core (electron acceptor) featuring highly conjugated systems (electron donor) with a length in the range 13–19 Å at C3. Among the most promising probes in terms of binding mode, theoretical affinity and polarity, BT1 has been synthesized and tested in vitro onto human induced pluripotent stem cells derived neuronal cell cultures. The probe showed excellent photophysical properties and high selectivity allowing in vitro imaging of hyperphosphorylated tau protein filaments with minimal background noise. Our findings offer new insight into the structure-activity relationship of this class of tau selective fluorophores, paving the way for boosting tau tangle detection in patients possibly through retinal spectral scans.

"Turn-On" Quinoline-Based Fluorescent Probe for Selective Imaging of Tau Aggregates in Alzheimer's Disease: Rational Design, Synthesis, and Molecular Docking.

Tau aggregation is believed to have a strong association with the level of cognitive deficits in Alzheimer's disease (AD). Thus, optical brain imaging of tau aggregates has recently gained substantial attention as a promising tool for the early diagnosis of AD. However, selective imaging of tau aggregates is a major challenge due to sharing similar β-sheet structures with homologous Aβ fibrils. Herein, four quinoline-based fluorescent probes (Q-tau) were judiciously designed using the donor-acceptor architecture for selective imaging of tau aggregates. In particular, probe Q-tau 4 exhibited a strong intramolecular charge transfer and favorable photophysical profile, such as a large Stokes' shift and fluorescence emission wavelength of 630 nm in the presence of tau aggregates. The probe also displayed a "turn-on" fluorescence behavior toward tau fibrils with a 3.5-fold selectivity versus Aβ fibrils. In addition, Q-tau 4 exhibited nanomolar binding affinity to tau aggregates (Kd = 16.6 nM), which was 1.4 times higher than that for Aβ fibrils. The mechanism of "turn-on" fluorescence was proposed to be an environment-sensitive molecular rotor-like response. Moreover, ex vivo labeling of human AD brain sections demonstrated favorable colocalization of Q-tau 4 and the phosphorylated tau antibody, while comparable limited staining was observed with Aβ fibrils. Molecular docking was conducted to obtain insights into the tau-binding mode of the probe. Collectively, Q-tau 4 has successfully been used as a tau-specific fluorescent imaging agent with lower background interference.

Optically superior fluorescent probes for selective imaging of cells, tumors, and reactive chemical species.

Fluorescent chemical probes have become powerful tools to study biological events in living cells. They provide a great opportunity to quantitatively and qualitatively analyze the physiological and biochemical properties of living cells in real time. The ability of researchers to manipulate these probes for a desired specific purpose has turned many heads in the scientific community. Despite a slow start, fluorescent probe research has seen exponential growth over the last decade in the world. This change required some adventurous and creative scientists from different fields-like biology, medicine, and chemistry-to come together to facilitate the constant expansion of this field. This review article introduces some fundamental concepts related to fluorescent probe designing and development. It also summarizes various fluorescent probes with superior optical properties used in fields like cell biology, cellular imaging, medical research, and cancer diagnosis. It is hoped that this article will encourage more young and creative scientists to contribute their talents to this field.

Didactic approach recounting advances and limitations in novel glutathione and cysteine detection (reduced GSH probe) with mixed coumarin, aldehyde, and phenyl-selenium chemistry.

We describe the pertinent research steps and analysis, many of which are chemical, to achieve a novel molecular probe for glutathione (GSH) which has been published and patented based on two recent articles: "Exceptional time response, stability and selectivity in doubly-activated phenyl selenium-based glutathione-selective platform" and "Enhanced Doubly Activated Dual Emission Fluorescent Probes for Selective Imaging of Glutathione or Cysteine in Living Systems" (Kim et al., 2015; Mulay et al., 2018). The papers involve coumarin probes. Reaction/detection unfolds with aminothiol attack at an electrophilic ring carbon position. An adjacent -CHO group is heavily involved in resonance aspects of the C-Se position, as well as the binding of the pendant N-group; the coumarin lactone carbonyl also allows for resonance to be achieved (vide infra). The leaving group, -SePh, while precedented in some systems, depends on electronic tuning (Fig. 1). For 1, the response times with GSH was ~100ms; a 100-fold fluorescence increase is observed (Compound 1). The probe also reacts with cysteine (Cys) and homocysteine (Hcy), albeit differently. For glutathione probing, the greater wavelength maxima (1: 550nm, DACP-1: 555nm, DACP-2: 590nm) enabled eventual cell studies (confocal microscopy) and animal studies. The limits of detection (LOD, 1: 270nM DACP-1: 10.1nM DACP-2: 17.0nM), as measured using the 3σ/k method. We provide a didactic presentation from probe conception to probe in vivo testing, etc., with additional considerations presented; a variety of factors/issues (2.1-2.28) help maintain a realistic sequence, a flow from wider to narrower, of the factors that go into developing medical, biological and neurodegenerative disease-related probes, meant to help other researchers follow our intention, gain perspective, and overcome current limitations.

A novel fluorescent probe for selective imaging of cellular cysteine with large Stokes shift and high quantum yield

A new strategy endowing probe with large Stokes shift, high quantum yield and red emission was developed by incorporating tetrahydroquinoxaline unit and five-membered pyrrolidine ring on fluorophore. As demonstrated, a novel probe was rationally designed and synthesized for sensitive monitor of cellular cysteine (Cys) and endogenous aminoacylase with large Stokes shift and high quantum yield.

Mitochondria-targeting near-infrared ratiometric fluorescent probe for selective imaging of cysteine in orthotopic lung cancer mice

Cysteine (Cys) plays significant roles in many physiological processes, although its normal concentration is maintained at the micromole level. Abnormally high levels of intracellular Cys can lead to many diseases including cancer. Recent years, many effective fluorescent probes have been developed for the selective detection of Cys against other biological thiols. Herein, we synthesized a ratiometric near-infrared (NIR) fluorescent probe Cy-OAcr for selective imaging of intracellular Cys. Cy-OAcr has a lipophilic iminium cation unit as the mitochondrial guider and an acrylate group as the Cys recognition unit as well as a fluorescence modulator for rearranging the conjugated π-electron system of cyanine fluorophore. Upon detection of Cys, there occurs a significant absorption and fluorescence spectral shift, which are desirably beneficial for ratiometric detection. This probe has high sensitivity and selectivity for Cys detection over glutathione (GSH), homocysteine (Hcy), and other biomolecules with a low limit of detection at 0.09 μM. Probe Cy-OAcr is capable to detect and image Cys in three living cancer cell lines and their corresponding tumor-bearing mice models. More importantly, we successfully apply this fluorescent probe to evaluate the level of Cys in orthotopic lung cancer model. Imaging analyses reveal that the probe can discriminate tumor lesions from normal tissues, indicating its significant potential applications for clinical auxiliary diagnosis of cancer.

Enhanced Doubly Activated Dual Emission Fluorescent Probes for Selective Imaging of Glutathione or Cysteine in Living Systems.

The development of novel fluorescent probes for monitoring the concentration of various biomolecules in living systems has great potential for eventual early diagnosis and disease intervention. Selective detection of competitive species in biological systems is a great challenge for the design and development of fluorescent probes. To improve on the design of fluorescent coumarin-based biothiol sensing technologies, we have developed herein an enhanced dual emission doubly activated system (DACP-1 and the closely related DACP-2) for the selective detection of glutathione (GSH) through the use of one optical channel and the detection of cysteine (Cys) by another channel. A phenylselenium group present at the 4-position completely quenches the fluorescence of the probe via photoinduced electron transfer to give a nonfluorescent species. Probes are selective for glutathione (GSH) in the red region and for cysteine/homocysteine (Cys/Hcy) in the green region. When they were treated with GSH, DACP-1 and DACP-2 showed strong fluorescence enhancement in comparison to that for closely related species such as amino acids, including Cys/Hcy. Fluorescence quantum yields (ΦF) increased for the red channel (<0.001 to 0.52 (DACP-1) and 0.48 (DACP-2)) and green channel (Cys) (<0.001 to 0.030 (DACP-1) and 0.026 (DACP-2)), respectively. Competing fluorescent enhancements upon addition of closely related species were negligible. Fast responses, improved water solubility, and good cell membrane permeability were all properly established with the use of DACP-1 and DACP-2. Live human lung cancer cells and fibroblasts imaged by confocal microscopy, as well as live mice tumor model imaging, confirmed selective detection.

Hexaphenylbenzene appended AIEE active FRET based fluorescent probe for selective imaging of Hg2+ ions in MCF-7 cell lines

Hexaphenylbenzene (HPB) appended rhodamine derivative 4 has been synthesized which exhibits aggregation-induced emission enhancement (AIEE) characteristics and forms fluorescent aggregates in mixed aqueous media. These aggregates show remarkable fluorescence resonance energy transfer (FRET) in the presence of Hg2+ ions among various metal ions tested. Further these aggregates were also utilized for the ratiometric imaging of Hg2+ ions in MCF-7 cell lines.

Carbazole-based two-photon fluorescent probe for selective imaging of mitochondrial hydrogen peroxide in living cells and tissues

The two-photon imaging in living cells and tissue demonstrated that the prepared probe possessed high specificity for mitochondrial H2O2.

Thrombin-mediated ratiometric two-photon fluorescent probe for selective imaging of endogenous ultratrace glutathione in platelet

Ultratrace change of reduced glutathione (GSH) can weaken coagulation function of platelet (PLT). Thus, rapid and sensitive imaging of GSH specific in PLT is beneficial for monitoring coagulation function of PLT. Many fluorescent probes for GSH have been reported, but ratio fluorescent probe with excellent two-photon property for screening PLT from peripheral blood and quantitative imaging of GSH are scarce. In this work, a thrombin-mediated two-photon GSH-specific fluorescent probe (IQDC-L) was reported. Sulfuric diamide, a key group as linker, was introduced into IQDC-L, which resulted in not only specific selectivity for GSH, but also FRET occurring in probe. When IQDC-L encountered GSH, “S–N” in sulfonamide group was cut off, and FRET was inhibited. Furthermore, fluorescence intensities at 520 and 595nm presented linear change on ratio mode in the range of GSH (2.0–65nM). The lowest detection for GSH was as low as 0.083nM. Intriguingly, IQDC-L under thrombin-mediated was able to screen PLT from peripheral blood without any interference. Thus, IQDC-L could be used to screen PLT from peripheral blood, and simultaneously, to in situ image ultratrace GSH.

Water-soluble colorimetric and ratiometric fluorescent probe for selective imaging of palladium species in living cells.

A novel water-soluble colorimetric and ratiometric fluorescent probe was synthesized and applied to imaging palladium species under physiological conditions in phosphate buffered saline (PBS) containing less than 1% organic cosolvent without adding any additional reagents. Based on palladium triggered terminal propargyl ethers cleavage reaction, the probe exhibited a high selectivity and sensitivity for palladium species of all the typical oxidation states (0, +2, +4), with a low detection limit (25 nM, 2.7 μg/L) and an obvious color change. Furthermore, the probe was successfully used for ratiometric fluorescence imaging of palladium in living cells.

A Reaction-Based Fluorescent Probe for Selective Imaging of Carbon Monoxide in Living Cells Using a Palladium-Mediated Carbonylation

Carbon monoxide is a member of the gasotransmitter family, which also includes NO and H(2)S, and has been implicated in a variety of pathological and physiological conditions. Whereas exogenous therapeutic additions of CO to tissues and whole animals have been well-studied, the real-time spatial and temporal tracking of CO at the cellular level remains an open challenge. Here we report a new type of turn-on fluorescent probe for selective CO detection based on palladium-mediated carbonylation reactivity. CO Probe 1 (COP-1) is capable of detecting CO both in aqueous buffer and in live cells with high selectivity over a range of biologically relevant reactive small molecules, providing a potentially powerful approach for interrogating its chemistry in biological systems.

Reaction-Based Fluorescent Probes for Selective Imaging of Hydrogen Sulfide in Living Cells

Hydrogen sulfide (H(2)S) is emerging as an important mediator of human physiology and pathology but remains difficult to study, in large part because of the lack of methods for selective monitoring of this small signaling molecule in live biological specimens. We now report a pair of new reaction-based fluorescent probes for selective imaging of H(2)S in living cells that exploit the H(2)S-mediated reduction of azides to fluorescent amines. Sulfidefluor-1 (SF1) and Sulfidefluor-2 (SF2) respond to H(2)S by a turn-on fluorescence signal enhancement and display high selectivity for H(2)S over other biologically relevant reactive sulfur, oxygen, and nitrogen species. In addition, SF1 and SF2 can be used to detect H(2)S in both water and live cells, providing a potentially powerful approach for probing H(2)S chemistry in biological systems.