Interaction between a novel intramolecular charge transfer fluorescent probe PFEP and human serum albumin

<正>The interaction mechanism between human serum albumin(HSA) and 1-phenyl-3(fluorenone-2-yl)-5-(9-ethylcarbazole-3-yl)-2- pyrazoline(PFEP) was investigated by fluorescence and absorption titration techniques in combination with molecular modeling method.Stern-Volmer plots at different temperatures proved that PFEP could quench the intrinsic fluorescence of HSA attributed to a static quenching procedure.The association constants were calculated in the range of 1×10~5-8×10~5mol~(-1) at different pH conditions,and the stoichiometric ratio of binding was 1:1 between PEEP and HSA.Molecular modeling study showed that the distance between indole moiety of the Trp214 residue and the carbazole group at the terminal of PFEP was 4.45 A in the optimal model.     

A novel near-infrared fluorescent probe was synthesized and its application in imaging of living cells

A novel near-infrared fluorescent probe, IR-736, was synthesized and applied to living cells. The probe exhibited good response fluorescent characteristic, and cells experiments showed the probe had high affinity and without apparent cytotoxicity. Fluorescent image experiments in living L929 cells, MCF-7 cells, HepG2 cells, further demonstrated its potential applications in biological systems. The probe effectively prevented the influence of autofluorescence and native cellular species in biological systems. It also exhibited good photostability, and excellent cell membrane permeability.     

A near-infrared fluorescent probe for monitoring ozone and imaging in living cells

A near-infrared fluorescent probe (Trp-Cy) for endogenous ozone is presented, which exhibited a large stokes shift about 140 nm and a rapid fluorescence response to ozone with high selectivity and sensitivity.     

A versatile water soluble fluorescent probe for ratiometric sensing of Hg2+ and bovine serum albumin

A novel tetraazamacrocycle fluorescent sensor (6-(1-(dimethylamino)-5-naphthalene sulfonyl)-3,6,9,15-tetraazabicyclo[9.3.1] pentadeca-1(15),11,13-triene, 1) has been designed and prepared, which can be utilized for selective and ratiometric sensing of Hg(2+) and bovine serum albumin (BSA) with two different responsive modes in aqueous solution at physiological pH (50 mM Tris-HCl, pH 7.6). Above 0.5 ppb Hg(2+) can be discerned by coordination with 1 and the emission color changes enable 1 to be applied to a fast Hg(2+) test paper assay. Sensor 1 has also been demonstrated to be easily cell-penetrable and applicable for Hg(2+) imaging in living cells. Imaging of BSA in the gel using SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) stained in the medium containing 1 verified that the binding of 1 and BSA was successful in the presence of nonprotein substances. The linear range of 1 towards BSA utilizing ratiometric fluorescent calibration via noncovalent interaction in solution is 0-100 μg mL(-1) with a detection limit of 1 μg mL(-1), and has been successfully employed to determine the albumin concentration in blood serum by means of ratiometric fluorescent measurements for the first time. Finally, sensor 1 behaves as a fluorescent molecular switch composed of triple logic gates upon chemical inputs of Hg(2+) and BSA, which potentially provides intelligent diagnostics for Hg(2+) contaminated serum on the nanoscale.     

An AIEE polyelectrolyte as a light-up fluorescent probe for heparin sensing in full detection range

Polyelectrolyte PTPEPyH, containing tetraphenylethene (TPE) and pyridinium, was synthesized. Its optical properties were investigated with spectroscopies and the results showed that there were two emission-enhanced stages in the interaction between positive-charged PTPEPyH and negative-charged biomacromolecule heparin. The mechanism was very different due to the reduced non-radiative energy loss and the change of surroundings. The polyelectrolyte PTPEPyH, compared with ChS and HA, also showed high selectivity for heparin in the buffer solution and could be used as a potential bio-probe for heparin quantification in the clinical full range.     

A near-infrared large Stokes shift probe based enhanced ICT strategy for F- detection in real samples and cell imaging

In view of the few reports of the near-infrared emissive probe for fluorine ions, we herein designed and synthesized a new easy-to-get colorimetric and near-infrared emissive fluorescent probe (IS-NR-F) with a large Stokes shift (>127 nm). Based on specific F^? triggered desilylation reaction induced enhanced ICT strategy involving the donor phenolate anion and the acceptor malononitrile, the probe exhibited dual colorimetric and fluorescent turn-on responses, and provided excellent selectivity for fluoride ions. The fluorescent response at 665 nm displayed very good linear relationship in the wide concentration range and deduced a low detection limit of 0.09 ppm. The detection mechanism was confirmed by ¹H NMR, ESI-MS, and TLC calculation. Moreover, probe IS-NR-F has been successfully employed to detect F^? in tap water, toothpaste samples, and fluorescent imaging of F^? in HeLa cells.     

A colorimetric and ratiometric fluorescent probe for quantification of bovine serum albumin

A 4-aminonaphthalimide-based ratiometric fluorescent probe 1 employing the internal charge transfer (ICT) mechanism was designed and synthesized to detect bovine serum albumin (BSA). The interaction of 1 and BSA was investigated by fluorescence and UV-vis absorption spectroscopy. Upon treatment with BSA, the probe successfully exhibited a ratiometric fluorescent response at 540 nm and 480 nm. The fluorescent intensity ratio at 540 nm and 480 nm (F(540)/F(480)) increases linearly with BSA concentration in the range of 0-75.0 μg mL(-1) and the detection limit was about 2.4 ng mL(-1). Our strategy is expected to provide a methodology to quantify BSA either by a normal or by a ratiometric and colorimetric way with high sensitivity.     

Pyridine-Si-xanthene: A novel near-infrared fluorescent platform for biological imaging

A novel near-infrared fluorescent platform with intrinsic lysosome-targeting was reported capable of detecting cysteine in living cells and in vivo.     

A novel lophine-based fluorescence probe and its binding to human serum albumin

The binding of a lophine-based fluorescence probe, 4-[4-(4-dimethylaminophenyl)-5-phenyl-1H-imidazol-2-yl]benzoic acid methyl ester (DAPIM) with human serum albumin (HSA) was investigated by fluorescence spectroscopy under physiological conditions. While DAPIM shows extreme low fluorescence in aqueous solution, DAPIM binding with HSA emits strong fluorescence at 510 nm. The binding constant and binding number determined by Scatchard plot was 3.65 × 10⁶ M⁻¹ and 1.07, respectively. Competitive binding between DAPIM and other ligands such as warfarin, valproic acid, diazepam and oleic acid, were also studied fluorometrically. The results indicated that the primary binding site of DAPIM to HSA is site II at subdomain IIIA. DAPIM can be a useful fluorescence probe for the characterization of drug-binding sites. In addition to the interaction study, because the fluorescence intensity of DAPIM increased in proportion to HSA concentration, its potential in HSA assay for serum sample was also evaluated.     

Development of a light-up fluorescent probe for HRAS G-quadruplex DNA

The development of small-molecule G-quadruplex DNA probes has attracted significant attention in recent years. However, G-quadruplexes can display a wide variety of topologies, which process different structures and functions. Therefore, selective discrimination one G-quadruplex structure over another is promising. Herein, we reported the design, synthesis and biological evaluation of a long-chain fatty amine functionalized triphenylamine-quinolinium conjugate 1b. Significant enhancement of the fluorescence intensity (over 180 fold) was observed when 1b bound with HRAS G-quadruplex DNA, while much weaker enhancements were presented in the presence of other G-quadruplexes (45–90-fold) and single/double-stranded DNAs (less than 20-fold), indicating 1b had an excellent selectivity to HRAS. The details of the interactions were investigated by UV–Vis, FID and CD analysis. The results show 1b could interact and stabilize HRAS structure mainly by π-π stacking binding mode. The introduced amine chain of the structure core was found to be better in the terms of inducing selectivity toward G-quadruplex structure. In addition, the application of 1b as a fluorescent agent for living cell imaging was also demonstrated.     

A near-infrared reversible fluorescent probe for peroxynitrite and imaging of redox cycles in living cells

BzSe-Cy is a small-molecule fluorescent probe containing Se, which can respond reversibly to changes in ONOO(-) or reduced ascorbate and exhibit high sensitivity and selectivity for ONOO(-).     

Development of a hypoxia-selective near-infrared fluorescent probe for non-invasive tumor imaging

A near-infrared fluorochrome, GPU-311, was designed, synthesized and evaluated for its application in non-invasive imaging of tumor hypoxia. Efficient synthesis was achieved by nucleophilic substitution and click chemistry ring using the bifunctional tetraethylene glycol linker 2 containing thiol and azide groups for the conjugation of the propargylated nitroimidazole 1 and the heptamethine cyanine dye 3 bearing a 2-chloro-1-cyclohexenyl ring. GPU-311 exhibited long excitation and emission wavelength (Ex/Em=785/802?nm) and a decent quantum yield (0.05). The water solubility and hydrophilicity of GPU-311 increased. After in vitro treatment of SUIT-2/HRE-Luc pancreatic cancer cells with GPU-311, a higher level of fluorescence was observed selectively in hypoxia than in normoxia. However, in vivo fluorescence imaging of a mouse xenograft model after GPU-311 administration revealed inadequate accumulation of GPU-311 in tumors due to its rapid elimination through the liver.     

A novel small-molecule near-infrared II fluorescence probe for orthotopic osteosarcoma imaging

Osteosarcoma is the most common primary malignant tumor of bone, particularly among children and adolescents. Advances in imaging, surgical techniques, and implants have dramatically reduced the need for amputation in the past three decades.Recently, in vivo fluorescence imaging in the second near-infrared window(NIR-II, 1,000–1,700 nm) shows impressive advantages of deeper tissue penetration and higher spatial resolution, which makes it a promising tool for the early diagnosis and post-operative observation of Osteosarcoma. To the best of our knowledge, this paper is the first time to develop a novel NIR-II fluorescence probe conjugated with an osteosarcoma targeted oligopeptide for molecular tumor imaging in a xenograft orthotopic osteosarcoma mouse model.     

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.     

Developing a genetically encoded green fluorescent protein mutant for sensitive light-up fluorescent sensing and cellular imaging of Hg(II)

Hg(II) is well-known for quenching fluorescence in a distance dependent manner. Nevertheless, when we exposed the fluorophore of a green fluorescent protein (GFP) toward Hg(II), through H148C mutation, the GFP fluorescence could be “lighted up” by Hg(II) down to sub-nM level. The detection linear range is 0.5–3.0 nM for protein solutions at 8.0 nM. The GFPH148C protein displayed a promising selectivity toward Hg(II) and also the cellular imaging capacity. Spectra measurements suggested that the ground-state redistribution of protein contributed to the fluorescence enhancement, which was found not limited to Hg(II), and thus presented an opening for building a pool of GFP-based chemosensors toward other heavy metal ions.     

A near-infrared fluorescent probe for lipid hydroperoxides in living cells

An NIR (near-infrared) fluorescent probe TCP (tricarbocyanine diphenylphosphine) including a non-conjugated 'pre-tricarbocyanine' was designed and synthesized for visualizing lipid hydroperoxides (ROOH) in living cells. The excitation and emission spectra of tricarbocyanine in the NIR region can effectively avoid background fluorescence interference in biological systems. The probe exhibited a rapid fluorescence response to ROOH and high selectivity for ROOH over other ROS (reactive oxygen species) and some biological compounds, and the limit of detection was 38 pM. In addition, the probe was stable, and less cytotoxic, which indicated that it has potential application in detecting lipid hydroperoxides in living biological systems.     

A dual near-infrared pH fluorescent probe and its application in imaging of HepG2 cells

A dual near-infrared pH fluorescent probe has been designed, synthesized and applied to HepG2 cells, with a pK(a) value of 5.14 under acidic conditions and 11.31 under basic conditions, which is valuable for studying acidic organelles in living cells and pH changes in chemical systems.     

The fluorescent probe prodan characterizes the warfarin binding site on human serum albumin

Abstract— The fluorescent probe Prodan (6-propionyl-2-dimethyl-aminonaphthalene) binds with high affinity to human serum albumin (HSA). The spectral characteristics of the Prodan bound to the protein are very different from the free Prodan in solution. These differences allowed the spectra to be deconvoluted into log-normal bands in order to quantify the bound and unbound ligand and to calculate the binding constant at different temperatures. From such temperature dependence, we found the binding to be exothermic with a van't Hoff enthalpy of -22.8 kJ mol^-1. Thermodynamic analysis suggests that the in teraction may be mainly caused by hydrophobic forces and electrostatic interactions. The above analysis of the spectra and the measures of the fluorescence polarization during the successive presence of six specific drugs suggest that the Prodan binding site corresponds with the warfarin binding site on HSA, whereas under the present experimental conditions the other characteristic binding sites of HSA were not affected. Thus, this fluorescent probe provides a rapid and simple means for the characterization of a specific binding site on HSA and also for detecting potential or nonspecific drug-protein interactions.     

Novel fluorescent probe based on dicoumarin for detection of hydrogen sulfide in real samples

A novel dicoumarin-derived hydrogen sulfide (H₂S) selective fluorescent “turn-on” probe 3-(2,4-dinitrobenzenesulfonate)-dicoumarin (DC-HS) created by covalent bonding between the 2,4-dinitrobenzenesulfonyl (DNBS) and the 3-hydroxy-dicoumarin (DC-OH) units. Upon the addition of H₂S, the probe DC-HS solution's fluorescence significantly increased, and its appearance is changed from practically colorless to brilliant yellow. Probe DC-HS also showed significant fluorescence amplification that was quantitatively detectable in the concentration range of 0–1.5 μM and had a low detection limit or limit of detection of 0.2 nM. Moreover, with a high recovery rate and excellent accuracy, the developed fluorescent molecule was used successfully for the analysis of H₂S in red wine samples.     

A selective near-infrared fluorescent probe for singlet oxygen in living cells

A selective near-infrared fluorescent probe (His-Cy), which features a fast response to (1)O(2) with high sensitivity and selectivity, was designed, synthesized and applied to bioimaging.