Synthesis of new acyclic chelators H4aPyta and H6aPyha and their complexes with Cu2+, Ga3+, Y3+, and Bi3.

In this article, we present the synthesis and characterization of new acyclic pyridine-containing polyaminocarboxylate ligands H4aPyta and H6aPyha, which differ in structural rigidity and the number of chelating groups. Their abilities to form complexes with Cu2+, Ga3+, Y3+, and Bi3+ cations, as well as the stability of the complexes, were evaluated by potentiometric titration method, radiolabeling with the corresponding radionuclides, in vitro studies, mass spectrometry, and HPLC. The structures of the resulting complexes were determined using NMR spectroscopy and DFT calculations. The results obtained made it possible to evaluate the influence of the structural features of the complexes on their stability. The developed chelators H4aPyta and H6aPyha were proved to be promising for further research in the field of radiopharmaceuticals.

Insights into Actinium Complexes with Tetraacetates─AcBATA versus AcDOTA: Thermodynamic, Structural, and Labeling Properties.

In the current research, we conducted a comparative study of the Ac3+ complex with H4DOTA and H4BATA. The stability constants of the [AcBATA]- and [AcDOTA]- complexes were studied directly by extraction methods. We discovered that the thermodynamic properties of the [AcBATA]- complex are superior to those of [AcDOTA]-. Moreover, the fast kinetics of H4BATA complexation with Ac3+ during the radiolabeling experiment was observed already at room temperature. Ac3+ was placed inside the macrocyclic cavity of the [AcBATA]- complex, preventing the release of the cation. According to DFT studies, two possible conformations were found, where two pendant arms coordinate with the metal cation on one side of the azacrown cavity and two on the other side, or three pendant arms are located on one side and one on the other. Finally, high inertness in vitro and in vivo of [AcBATA]- was discovered, making the H4BATA ligand highly preferable for application as a component of actinium-based radiopharmaceuticals.

Specific Fluorescent Probes for Imaging DNA in Cell-Free Solution and in Mitochondria in Living Cells.

New styryl dyes consisting of N-methylpyridine or N-methylquinoline scaffolds were synthesized, and their binding affinities for DNA in cell-free solution were studied. The replacement of heterocyclic residue from the pyridine to quinoline group as well as variation in the phenyl part strongly influenced their binding modes, binding affinities, and spectroscopic responses. Biological experiments showed the low toxicity of the obtained dyes and their applicability as selective dyes for mitochondria in living cells.

DNA-based assemblies with bischromophoric styryl dye-chromene conjugates and cucurbit[7]uril.

Novel conjugates consist of 4-styrylpyridinium dye and 2,2-diphenyl-2H-chromene moiety were obtained, and their affinity to double stranded DNA and cucurbit[7]uril was investigated. With a combination of absorption, fluorescence and circular dichroism spectroscopies as well as MALDI-TOF mass spectrometry, we demonstrate that these compounds can interact with macromolecules to form of the supramolecular assemblies due to two suitable binding sites. The ternary complex is formed as a result of the intercalation of a positively charged styryl part between DNA base pairs, while cucurbit[7]uril is located on the alkyl chain between two moieties of conjugate. All these findings provide valuable information into controlling the interaction between organic molecules, DNA and cucurbit[7]uril.

A New Glutathione-Cleavable Theranostic for Photodynamic Therapy Based on Bacteriochlorin e and Styrylnaphthalimide Derivatives.

Herein, we report a new conjugate BChl-S-S-NI based on the second-generation photosensitizer bacteriochlorin e6 (BChl) and a 4-styrylnaphthalimide fluorophore (NI), which is cleaved into individual functional fragments in the intracellular medium. The chromophores in the conjugate were cross-linked by click chemistry via a bis(azidoethyl)disulfide bridge which is reductively cleaved by the intracellular enzyme glutathione (GSH). A photophysical investigation of the conjugate in solution by using optical spectroscopy revealed that the energy transfer process is realized with high efficiency in the conjugated system, leading to the quenching of the emission of the fluorophore fragment. It was shown that the conjugate is cleaved by GSH in solution, which eliminates the possibility of energy transfer and restores the fluorescence of 4-styrylnaphthalimide. The photoinduced activity of the conjugate and its imaging properties were investigated on the mouse soft tissue sarcoma cell line S37. Phototoxicity studies in vitro show that the BChl-S-S-NI conjugate has insignificant dark cytotoxicity in the concentration range from 15 to 20,000 nM. At the same time, upon photoexcitation, it exhibits high photoinduced activity.

Fluorescent RET-Based Chemosensor Bearing 1,8-Naphthalimide and Styrylpyridine Chromophores for Ratiometric Detection of Hg2+ and Its Bio-Application.

Dyad compound NI-SP bearing 1,8-naphthalimide (NI) and styrylpyridine (SP) photoactive units, in which the N-phenylazadithia-15-crown-5 ether receptor is linked with the energy donor naphthalimide chromophore, has been evaluated as a ratiometric fluorescent chemosensor for mercury (II) ions in living cells. In an aqueous solution, NI-SP selectively responds to the presence of Hg2+ via the enhancement in the emission intensity of NI due to the inhibition of the photoinduced electron transfer from the receptor to the NI fragment. At the same time, the long wavelength fluorescence band of SP, arising as a result of resonance energy transfer from the excited NI unit, appears to be virtually unchanged upon Hg2+ binding. This allows self-calibration of the optical response. The observed spectral behavior is consistent with the formation of the (NI-SP)·Hg2+ complex (dissociation constant 0.13 ± 0.04 µM). Bio-imaging studies showed that the ratio of fluorescence intensity in the 440-510 nm spectral region to that in the 590-650 nm region increases from 1.1 to 2.8 when cells are exposed to an increasing concentration of mercury (II) ions, thus enabling the detection of intracellular Hg2+ ions and their quantitative analysis in the 0.04-1.65 µM concentration range.

Fluorescence turn-on probes for intracellular DNA/RNA distribution based on asymmetric bis(styryl) dyes.

Two bis(styryl) dyes, varying in type of spacer between two mono(styryl) units, were tested for interactions with ct-DNA or cl-RNA. Both compounds showed strong affinity toward ds-DNA/ss-RNA, the binding mode of the interaction is shifting between DNA groove binding to RNA intercalation. Consequently, interaction with DNA shows a stronger flare-up of fluorescence (151 times for dye 1 and 118 times for dye 2) than when binding with RNA (23 times and 36 times correspondingly). The presence of energy transfer in the bis(styryl) system increases the Stokes shift of the dye, so when irradiating the system in the region of 370-380 nm, fluorescence is detected at 610-620 nm. The biological experiments showed that the efficient intracellular fluorescence quench was observed in the DNase digest test suggested that dyes can be applied by recognition of DNA in the presence of RNA molecules.

Novel Hybrid Benzoazacrown Ligand as a Chelator for Copper and Lead Cations: What Difference Does Pyridine Make.

A synthetic procedure for the synthesis of azacrown ethers with a combination of pendant arms has been developed and the synthesized ligand, characterized by various techniques, was studied. The prepared benzoazacrown ether with hybrid pendant arms and its complexes with copper and lead cations were studied in terms of biomedical applications. Similarly to a fully acetate analog, the new one binds both cations with close stability constants, despite the decrease in both constants. The calculated geometry of the complexes correlate with the data from X-ray absorption and NMR spectroscopy. Coordination of both cations differs due to the difference between the ionic radii. However, these chelation modes provide effective shielding of cations in both cases, that was shown by the stability of their complexes in the biologically relevant media towards transchelation and transmetallation.

Influence of Copper Oxide Nanoparticles on Gene Expression of Birch Clones In Vitro under Stress Caused by Phytopathogens.

Recently, metal oxide nanoparticles (NPs) have attracted attention as promising components for the protection and stimulation of plant microclones in tissue culture in vitro. However, the effect of NPs on the genetic mechanisms underlying plant adaptive responses remains poorly understood. We studied the effect of column-shaped CuO NPs 50 nm in diameter and 70-100 nm in length at a concentration of 0.1-10 mg/L on the development of phytopathogenic fungi Alternaria alternata, Fusarium oxysporum, and Fusarium avenaceum in culture, as well as on the infection of downy birch micro-clones with phytopathogens and the level of genes expression associated with the formation of plant responses to stress induced by microorganisms. CuO NPs effectively suppressed the development of colonies of phytopathogenic fungi A. alternata and F. avenaceum (up to 68.42% inhibition at 10 mg/L CuO NPs) but not the development of a colony of F. oxysporum. Exposure to the NPs caused multidirectional responses at the level of plant genes transcription: 5 mg/L CuO NPs significantly increased the expression level of the LEA8 and MYB46 genes and decreased the expression of DREB2 and PAL. Infection with A. alternata significantly increased the level of MYB46, LEA8, PAL, PR-1, and PR-10 transcripts in birch micro-clones; however, upon exposure to a medium with NPs and simultaneous exposure to a phytopathogen, the expression of the MYB46, PR-1, and PR-10 genes decreased by 5.4 times, which is associated with a decrease in the pathogenic load caused by the effect of NPs and the simultaneous stimulation of clones in vitro. The results obtained can be used in the development of preparations based on copper oxide NPs for disinfection and stimulation of plant phytoimmunity during clonal micropropagation of tree crops.

Critical aspects of AlGaInP-based LED design and operation revealed by full electrical-thermal-optical simulations.

Coupled electrical-thermal-optical simulations of a high-power AlGaInP-based red light-emitting diode (LED) are reported and compared with detailed characterization data of the device available in literature. The simulations enabled identification of the most critical factors limiting the LED performance. Among them, the following ones are found to be of primary importance: (i) absorption of emitted photons in a p+-GaAs contact layer, limiting the light extraction efficiency; (ii) device self-heating producing thermally stimulated electron leakage into the p-side of the LED structure; and (iii) current crowding around small circular p-electrodes enhancing additionally the electron leakage. Possible room for efficiency improvement is estimated by modeling. Optimization of some structural units of the LED design is discussed as well as further directions of the simulation model improvements.

Photodiagnosis and photodynamic effects of bacteriochlorin-naphthalimide conjugates on tumor cells and mouse model.

Photo-induced cytotoxicity and antitumor activity of a series of dual function agents for photodynamic therapy (PDT) and fluorescent imaging based on bacteriochlorin photosensitizer conjugated with various naphthalimide fluorophores was studied in vitro using murine tumor cells of S37 sarcoma and in vivo on mice bearing murine S37 sarcoma. Upon irradiation at the absorption maximum of the photosensitizer, the activity of conjugates was as high as in the case of individual bacteriochlorin, while an additional excitation of the naphthalimide fragment led to an increase in the PDT efficacy due to resonance energy transfer from the fluorophore to photosensitizer. The fluorescence contrast and specific cytotoxic activity measurements indicate that the conjugate of bacteriochlorin with 3,4-dimethoxestyrene-substituted naphthalimide is the most promising agent for the application as theranostic in PDT.

Photochemical synthesis, intercalation with DNA and antitumor evaluation in vitro of benzo[d]thiazolo[3,2-a]quinolin-10-ium derivatives.

A new anticancer benzo[d]thiazolo[3,2-a]quinolin-10-ium derivatives were synthesized and characterized. Anticancer evaluation in vitro against four cancer cell lines including adenocarcinomic human alveolar basal epithelial cells (A549), hepatocellular carcinoma (HepG2), prostate cancer (PC3) and breast cancer (MCF7) indicated that some of prepared compounds shows higher selectivity in comparison with doxorubicin. DNA interaction studies by optical, CD, NMR spectroscopies showed the high affinity of benzothiazole ligands towards the dsDNA. The ligand-DNA interaction occurs through the intercalation of benzo[d]thiazolo[3,2-a]quinolin-10-ium derivatives with nucleic acid. The investigation of formed ligand - DNA complexes by docking and molecular dynamic calculations was applied for analysis of the relationship between structure and anticancer activity. The results suggested that benzo[d]thiazolo[3,2-a]quinolin-10-ium derivatives might serve as a novel scaffold for the future development to new antitumor agents.

Ratiometric Detection of Mercury (II) Ions in Living Cells Using Fluorescent Probe Based on Bis(styryl) Dye and Azadithia-15-Crown-5 Ether Receptor.

Bis(styryl) dye 1 bearing N-phenylazadithia-15-crown-5 ether receptor has been evaluated as a ratiometric fluorescent chemosensor for mercury (II) ions in living cells. In aqueous solution, probe 1 selectively responds to the presence of Hg2+ via the changes in the emission intensity as well as in the emission band shape, which is a result of formation of the complex with 1:1 metal to ligand ratio (dissociation constant 0.56 ± 0.15 µM). The sensing mechanism is based on the interplay between the RET (resonance energy transfer) and ICT (intramolecular charge transfer) interactions occurring upon the UV/Vis (380 or 405 nm) photoexcitation of both styryl chromophores in probe 1. Bio-imaging studies revealed that the yellow (500-600 nm) to red (600-730 nm) fluorescence intensity ratio decreased from 4.4 ± 0.2 to 1.43 ± 0.10 when cells were exposed to increasing concentration of mercury (II) ions enabling ratiometric quantification of intracellular Hg2+ concentration in the 37 nM-1 µM range.

Zinc and copper complexes with azacrown ethers and their comparative stability in vitro and in vivo.

Copper-based radiopharmaceuticals are of high interest these days owing to the decay properties of copper radioisotopes. In contrast, labeled zinc compounds have been less studied for applications in nuclear medicine. In this study, the stability of labeled zinc and copper complexes with two azacrown ether ligands was investigated and compared. Then, the in vitro and in vivo stability of the studied zinc complexes was demonstrated, with the complexes showing promise for biomedical applications. In contrast, analogous copper complexes quickly dissociated in the presence of serum proteins. Furthermore, a simple method for the production of radiochemically pure 65Zn was proposed, and the opportunity for its use as a surrogate radionuclide for research into potential zinc-containing radiopharmaceuticals was demonstrated.

Cucurbit[7]uril-driven modulation of ligand-DNA interactions by ternary assembly.

The design of small organic molecules with a predictable and desirable DNA-binding mechanism is a topical research task for biomedicine application. Herein, we demonstrate an attractive supramolecular strategy for controlling the non-covalent ligand-DNA interaction by binding with cucurbituril as a synthetic receptor. With a combination of UV/vis, CD and NMR experiments, we demonstrate that the bis-styryl dye with two suitable binding sites can involve double stranded DNA and cucurbituril in the formation of the supramolecular triad. The ternary assembly is formed as a result of the interaction of macrocyclic cucurbituril with one pyridinium fragment of the bis-styryl dye, while the second pyridinium fragment of the dye is effectively associated with DNA backbones, which leads to a change in the ligand-DNA binding mode from aggregation to a minor groove. This exciting outcome was supported by molecular docking studies that help to understand the molecular orientation of the supramolecular triad and elucidate the destruction of dye aggregates caused by cucurbituril. These studies provide valuable information on the mechanisms of DNA binding to small molecules and recognition processes in bioorganic supramolecular assemblies constructed from multiple non-covalent interactions.

Encapsulation-Controlled Photoisomerization of a Styryl Derivative: Stereoselective Formation of the Anti Z-Isomer in the Cucurbit[7]uril Cavity.

The photochemical isomerization of a styrylpyridinium dye (SP) bearing an unsymmetrically attached benzo-15-crown-5 ether has been studied in aqueous solution in the absence and presence of cucurbit[7]uril (CB[7]). The detailed analysis of the UV/Vis and NMR spectra showes that the isomeric composition of the photostationary mixtures of SP can be modulated by the host-guest complexation with CB[7]. It was found that steric hindrance caused by encapsulation of SP in the host cavity induces the exclusive formation of the anti conformer of Z-SP in contrast with the mixture of both anti and syn conformers obtained during photoisomerization of the dye without CB[7]. Remarkably, the displacement of anti Z-SP from CB[7] does not lead to the transformation of the anti Z-isomer into the syn Z-isomer pointing out the conformational memory of the system. The results provide an interesting example of the supramolecular stereorecognition by the achiral CB[7] host.

Benzoazacrown compound: a highly effective chelator for therapeutic bismuth radioisotopes.

A new benzoazacrown ligand H4BATA was synthesized and its complexation ability towards bismuth cations was evaluated. Binding of cation occurs at room temperature in a few minutes and formed complex exhibits the same level of inertness as highly stable complex with the well-known H4DOTA in biologically relevant and challenging media under in vivo conditions.

Synthesis of fused heterocyclic systems via the Mallory photoreaction of arylthienylethenes.

Photochemical oxidative cyclization of 2- and 3-thienylstilbenes (heterostilbenes) containing mono-, di- and trimethoxy groups in the benzene ring or heterocyclic fragment results in the formation of isomeric thieno-annelated polycyclic aromatic compounds demonstrating optical properties that differ from those of initial stilbene derivatives. The structures of cyclic products were evaluated via1H and 13C NMR, HRMS, elemental analysis and X-ray crystallography. The research was aimed to study the effect of substituents in stilbene derivatives of thiophene as well as the position of the styryl fragment in the thiophene nucleus on the occurrence of photocyclization reactions.

The regioselective [2 + 2] photocycloaddition reaction of 2-(3,4-dimethoxystyryl)quinoxaline in solution.

Herein, the [2 + 2] photocycloaddition between two molecules of (E)-2-(3,4-dimethoxystyryl)-quinoxaline (1) in an acetonitrile solution to form only one cyclobutane isomer out of eleven possible isomers is described. The observed photocycloaddition reaction is reversible; thus, the studied photocycloaddition reaction can be considered as a photoreversible photochromic process. The removal of two methoxy groups from the (E)-2-(3,4-dimethoxystyryl)quinoxaline (1) structure produces compound 2, which participates only in the photoisomerization reaction. The change of the quinoxaline residue in 1 to quinoline results in the formation of compound 3, which demonstrates the regioselective oxidization electrocyclic transformation through the formation of a novel C-N bond.

Thiourea Modified Doxorubicin: A Perspective pH-Sensitive Prodrug.

A novel approach to the synthesis of pH-sensitive prodrugs has been proposed: thiourea drug modification. Resulting prodrugs can release the cytotoxic agent and the biologically active 2-thiohydantoin in the acidic environment of tumor cells. The concept of acid-catalyzed cyclization of thioureas to 2-thiohydantoins has been proven using a FRET model. Dual prodrugs of model azidothymidine, cytotoxic doxorubicin, and 2-thiohydantoin albutoin were obtained, which release the corresponding drugs in the acidic environment. The resulting doxorubicin prodrug was tested on prostate cancer cells and showed that the thiourea-modified prodrug is less cytotoxic (average IC50 ranging from 0.5584 to 0.9885 µM) than doxorubicin (IC50 ranging from 0.01258 to 0.02559 µM) in neutral pH 7.6 and has similar toxicity (average IC50 ranging from 0.4970 to 0.7994 µM) to doxorubicin (IC50 ranging from 0.2303 to 0.8110 µM) under mildly acidic conditions of cancer cells. Cellular and nuclear accumulation in PC3 tumor cells of Dox prodrug is much higher than accumulation of free doxorubicin.