Synthesis structural and spectroscopic properties of quinoxaline-bridged bisBODIPYs

Two novel quinoxaline-bridged bisBODIPYs have been synthesized by the condensation of 2,3-bis(5-formylpyrrol-2-yl)quinoxaline with 3-ethyl-2,4-dimethylpyrrole followed by a modification using a Knoevenagel reaction. They were well characterized by X-ray diffraction, NMR, HRMS UV-vis and fluorescence spectroscopy. These two quinoxaline-bridged bisBODIPYs have unusual broad absorption bands, which are different from those of typical BODIPYs They exhibit broad red-shifted emission bands centered at around 610 nm and 730 nm respectively with larger Stokes shifts at the range of 1421–2136 cm[Formula: see text] Both bisBODIPYs show different extent solvent-dependent fluorescence and exhibit fluorescence quenching in polar solvents due to the existence of possible intramolecular charge transfer.

Copper-catalyzed α-benzylation of BODIPYs via radical-triggered oxidative cross-coupling of two C–H bonds

An oxidative cross-dehydrogenative coupling of BODIPYs with toluene and it derivatives has been developed, allowing for the facile synthesis of a broad range of structurally diverse α-benzylated BODIPYs with high solid-state fluorescence.

Synthesis, Structure, and Properties of Near-Infrared [b]Phenanthrene-Fused BF2 Azadipyrromethenes

A new class of phenanthrene-fused BF₂ azadipyrromethene (azaBODIPY) dyes have been synthesized through a tandem Suzuki reaction and oxidative ring-fusion reaction, or a palladium-catalyzed intramolecular C-H activation reaction. These phenanthrene-fused azaBODIPY dyes are highly photostable and display markedly redshifted absorption (up to λ=771 nm) and emission bands (λ≈800 nm) in the near-infrared region. DFT calculations and cyclic voltammetry studies indicate that, upon annulation, more pronounced stabilization of the LUMO is the origin of the bathochromic shift of the absorption and high photostability.

PyrrolylBODIPYs: Syntheses, Properties, and Application as Environment-Sensitive Fluorescence Probes

Four pyrrole B-ring-functionalized pyrrolylBODIPYs and their B-ring unsubstituted analogues were synthesized from easily accessible starting 5-halo-2-formylpyrroles and were characterized by nuclear magnetic resonance, high-resolution mass spectrometry, X-ray analysis, and optical/electronic properties. In great contrast to the substitution(s) at the other two pyrrolic units, electron-donating substituent(s) at pyrrole B-ring bring significant blue shift of the absorption and emission bands. Cyclic voltammetry and density functional theory calculations indicate that this blue shift may be attributed to the increased highest occupied molecular orbital and the lowest unoccupied molecular orbital energy levels and the overall increase in the energy band gaps. These pyrrolylBODIPYs generally show intense absorption (centered at 570-624 nm) and fluorescence emission (582-654 nm) in nonpolar solvents. A gradual decrease in the fluorescence intensity was observed for these dyes with the increase in solvent dipolar moment, which combines with the red to far-red absorption/emission, rendering these pyrrolylBODIPYs potential applications as environment-sensitive fluorescence probes as demonstrated in this work for bovine serum albumin.

Synthesis, Structure, and Properties of β-Vinyl Ketone/Ester Functionalized AzaBODIPYs from FormylazaBODIPYs

Postfunctionalization of azaBODIPY (the BF₂ complex of azadipyrromethene) is highly desirable due to the strong tunable absorption bands at wavelengths above 650 nm and the wide-ranging applications of this class of dyes in biomedicine and materials science. Currently available postfunctionalization methods for this class of dyes have been limited to the Pd-catalyzed coupling reactions on β-halogenated (brominated or iodinated) azaBODIPY platforms. In this work, we report a new strategy for the facile postfunctionalization of the azaBODIPY chromophore with various vinyl ketone and vinyl esters based on a Wittig reaction on our previously developed β-formylazaBODIPYs and our recently developed β-bromo-β'-formylazaBODIPYs. Our strategy uses easily accessible starting materials and mild reaction conditions. It is highly compatible with various common phosphonium ylides (aliphatic, aromatic, and ester substituted ones). These resultant bromo-containing β-vinyl ketone/ester functionalized azaBODIPYs are potential photosensitizers and can be further functionalized via coupling reactions. The ester groups on some of these resultant azaBODIPYs can be further hydrolyzed to achieve the desired water solubility and conjugate with the biomolecule and solid surface.

High Yield of Rodent Islets with Intraductal Collagenase and Stationary Digestion—A Comparison with Standard Technique

Intraductal distention of the pancreas with collagenase followed by stationary warm incubation improves the recovery of islets of Langerhans in the rat, but controlled studies are needed for valid comparison with standard isolation methods. We have modified Gotoh's technique of stationary digestion for high-yield isolation in the rat (Stationary). The method is subjected herein to rigorous blinded comparison with the standard chopped tissue (Chopped) technique, based on Lacy et al., as performed in our laboratory for over 10 yr. Islet recovery was determined by a single observer ‘blinded’ to the method of isolation used, and only intact islets of diameter ≥ 100 μm were included. Stationary gave 719 ± 114 islets per pancreas (mean ± SD, n = 21 isolations) vs. 487.5 ± 69 for Chopped (n = 36 isolations), a 47.5% increment in yield (p < 0.0001). In vitro islet perifusion showed no statistical difference in stimulation index (SI) or stimulated area under the curve (SAUC) between the two methods, but Stationary showed a trend towards improved phase II insulin release. In vivo function was assessed by isogeneic transplantation of 2,000 islets beneath the renal capsule of streptozotocin diabetic recipients (65 mg/kg Sigma); Stationary recipients (n = 7) became normoglycemic (≤ 8 mmol/L) by 3.3 ± 4.8 days vs. 1.6 ± 1.5 days for Chopped recipients (p = 0.4 ns, mean ± SEM). IVGTT performed at 1 mo posttransplant gave K-values for Stationary of 2.64 ± 0.8 vs. 2.62 ± 0.8 for Chopped (mean ± SD, p = 0.9 ns, n = 6, unpaired t-test), which were not distinguishable from normal control rats (2.59 ± 0.8) (p = 0.9 ns, n = 10). Graft function remained stable until graft bearing nephrectomy induced hyperglycemia uniformly within 1 day. Graft histology showed a healthy well-preserved structure on light microscopy, with well-granulated beta cells on EM. Economic costs of rat, collagenase, and Ficoll were 26% ($50.82) lower per recipient for Stationary. We conclude that modified stationary digestion significantly improves islet recovery with excellent in vitro and in vivo function, and is cost effective.

Synthetically simple, click-generated quinoline-based Fe3+ sensors

Simple quinoline-based fluorescent probes for Fe³⁺ have been efficiently synthesized through 'click' reaction. Both probes gave intense fluorescence compared to 8-hydroquinoline in various organic solvents due to the inhibition of the excited state intramolecular photon transfer process, while showing dramatically quenched and red-shifted fluorescence in an aqueous solution, which can be attributed to the hydrogen bond-induced intermolecular excited state proton transfer process. In the presence of Fe³⁺ or in an acidic condition (pH less than 4.0), both probes showed similar quenching of the emission and over 100 nm red-shifts of their emission maxima. The binding mode between the probes and Fe³⁺ has been found to be 1:1 based on Job's plot. A highly sensitive and selective response in their absorption and emission towards Fe³⁺ over many other metal ions, including Cr³⁺ and Cu²⁺, was observed and may be the result of the ground state metal to ligand charge transfer effect from Fe³⁺ to quinoline ligands.

One-pot synthesis and properties of well-defined butadiynylene-BODIPY oligomers

A homogeneous series of oligo-butadiynylene-BODIPYs containing up to four BODIPY moieties have been synthesized in one pot, and from which a soluble, red emitting butadiyne-linked dimer, which can ratiometrically detect viscosity, was developed.

Up-regulation of miR-888-5p in hepatocellular carcinoma cell lines and its effect on malignant characteristics of cells

MicroRNA (miRNA) expression has been linked to the molecular pathogenesis of hepatocellular carcinoma (HCC). The aberrant expression of miRNA is involved in the processes of tumorigenesis and cancer progression. According to the latest research, miR-888-5p is associated with strong cancer-promoting effect. For instance, miR-888-5p is up-regulated in prostate cancer and breast cancer. Nevertheless, the role of miR-888-5p in HCC has not been investigated to date. In this study, we found that miR-888-5p levels in four HCC cell lines (SMMC7721, HepG2, Huh-7 and Bel7402) were significantly up-regulated compared with human hepatocyte cell line (HHL-5). After transiently transfected with miR-888-5p mimic, our results demonstrated that miR-888-5p plays a major role in promoting the proliferation and metastatic potential of HCC cells. Moreover, miR-888-5p also increased the expression of MMP-2 and MMP-9 proteins which account for cell migration and invasion, and decreased the expression of p53 protein which further promoted malignance of HCC. Therefore, miR-888-5p may be considered a potential biomarker for diagnostics and prognosis of HCC.

Bu4NI/tBuOOH catalyzed, α-regioselective cross-dehydrogenative coupling of BODIPY with allylic alkenes and ethers

A Bu₄NI/tBuOOH-catalyzed, highly regioselective cross-dehydrogenative coupling (CDC) of the α-C–H bond(s) of the BODIPY core has been developed.

Regioselective and Stepwise Syntheses of Functionalized BODIPY Dyes through Palladium-Catalyzed Cross-Coupling Reactions and Direct C-H Arylations

Regioselective and stepwise syntheses of a series of functionalized BODIPY dyes through palladium-catalyzed cross-coupling reactions and direct C-H arylations have been developed. In particular, this method allows the straightforward synthesis of 2,6-dibromo-3,5-diarylBODIPYs and 2-bromo-3-arylBODIPYs from polybrominated BODIPYs. The X-ray structure of intermediates 5a-c indicated that the palladium was first inserted into the C-Br bonds at 3,5-positions of brominated BODIPYs. The resulting 2,6-dibromo-substituted BODIPYs are potential long wavelength photosensitizers which are not easily accessible using previous methods.

Synthesis and photophysical properties of meso-aryloxy linked BODIPY monomers, dimers, and trimer

A series of meso-aryloxy linked BODIPY monomers, dimers and trimer were synthesized by nucleophilic aromatic substitution (SNAr) reaction from phenols with meso-chloro BODIPY and their photophysical properties were systematically studied by UV-vis and fluorescence spectroscopy. The relationship between their photophysical properties and the spatial arrangement of meso-aryloxy linked BODIPYs has been discussed. The monomers exhibited different extent solvent-dependent fluorescence, and fluorescence quenching in polar solvents were found relative to the HOMO energies of the donor (meso-phenols), indicating possible PET effect from meso-phenols to the BODIPY fluorophore. Ortho-dimer showed unusual broad red-shifted emission bands centered at 550 nm with a larger Stokes shifts at the range of 2900–3400 cm[Formula: see text], and low fluorescence quantum yields, which was in sharp contrast to those of other dimers and trimer, indicating of possible excimeric species formation due to slipped cofacial arrangement ofortho-dimer.

Visible light excitable 3-formylBODIPYs for selective fluorescent and colorimetric sensing of cysteine

Selective fluorescent and colorimetric sensing of cysteine in methanol-HEPES buffer (45 mM, pH [Formula: see text] 7.2, v/v [Formula: see text] 1/1) solution over various common amino acids and related thiol containing compounds has been achieved based on the cyclization reaction between the formyl group on 3-formylBODIPYs and cysteine/homocystein. Upon addition of cysteine/homocystein, 3-formylBODIPYs exhibited greatly enhanced fluorescence intensity as well as an abvious red-shift of the absorption peak (20–30 nm). The detection limits for cysteine were in the range of 1.18–2.73 [Formula: see text]10[Formula: see text] M. The detection mechanism was studied by nuclear magnetic resonance and theoretical calculation.

Metal-Free Direct α-Selective Arylation of Boron Dipyrromethenes via Base-Mediated C-H Functionalization

A metal-free direct α-selective arylation of BODIPYs has been developed based on base-mediated C-H functionalization with easily accessible diaryliodonium salts, which provides a straightforward facile access to a variety of α-arylBODIPY dyes. The α-regioselectivity was confirmed by X-ray analysis, and was studied by DFT calculation. The resultant dyes show strong absorption and emission over a broad range of spectra tunable via the simple variation of the diaryliodonium salts.