A tetrahydroacridine derivative and its conjugate with gold nanoparticles: promising agents for the treatment of Alzheimer's disease.

A new tetrahydroacridine derivative (CHDA) with acetylcholinesterase inhibitory properties was synthesized. Using a range of physicochemical techniques, it was shown that the compound strongly adsorbs onto the surface of planar macroscopic or nanoparticulate gold, forming a nearly full monolayer. The adsorbed CHDA molecules reveal well-defined electrochemical behavior, being irreversibly oxidized to electroactive species. The CHDA also exhibits strong fluorescence, which is effectively quenched after adsorption onto gold via a static quenching mechanism. Both CHDA and its conjugate reveal considerable inhibitory properties against acetylcholinesterase activity, which is promising from the perspective of therapeutic application in the treatment of Alzheimer's disease. Moreover, both agents appear to be non-toxic as demonstrated using in vitro studies. On the other hand, conjugation of CHDA with nanoradiogold particles (Au-198) offers new potential diagnostic perspectives in medical imaging.

Choline chloride-formic acid mixture as a medium for the reduction of pertechnetates - electrochemical and spectroscopic studies.

The physicochemical properties of a choline chloride (ChCl) and formic acid (FA) mixture (1 : 2 molar ratio) have been studied over a broad range of temperatures (-140 to 60 °C). Differential scanning calorimetry has shown that the examined system remains in the liquid state at very low temperatures - a glass transition is observed in the range of -125 °C to -90 °C. The kinematic viscosity, ionic conductivity and the width of the electrochemical window determined for this system revealed its beneficial electrochemical properties. This indicates the suitability of ChCl : FA electrolytes in electrochemical measurements. In this non-aqueous electrolyte, electrochemical reduction of Tc(VII) ions has been studied for the first time. Cyclic voltammetry and chronopotentiometry experiments revealed that the electroreduction of pertechnetates is a multi-path process which leads to the formation of a Tc(IV) ionic form. X-Ray absorption spectroscopy of the latter revealed its structure as a TcCl62- complex.

Preparation of Surface-Supported Polylactide Spherical-Cap Particles.

Biodegradable polymer particles are of considerable importance due to their multiple applications in medical diagnostics and therapy. Spherical-cap particles have been prepared in a very general and simple method by melting a thin polymer film supported on a solid substrate that is in contact with a hydrophilic solvent. The melted polymer forms droplets which transform into solid particles attached to the surface after cooling down the sample. This approach has been demonstrated for polylactide adlayers on glass, which, when melted in glycerol, produce an array of polymer particles supported on the surface. The size of the particles depends on the experimental conditions and ranges from tens of nanometers to several micrometers. The particles can be employed to incorporate guest species, for example, drug molecules or inorganic nanoparticles. This has been confirmed herein through entrapment of an anticancer drug (doxorubicin) and radiogold (Au-198) nanoparticles. The resulting structures have been examined using a number of complementary physicochemical techniques including scanning and transmission electron microscopy, atomic force and optical microscopy as well as Raman and fluorescence spectroscopy.

Potential Application of Ionic Liquids for Electrodeposition of the Material Targets for Production of Diagnostic Radioisotopes.

An overview of the reported electrochemistry studies on the chemistry of the element for targets for isotope production in ionic liquids (ILs) is provided. The majority of investigations have been dedicated to two aspects of the reactive element chemistry. The first part of this review presents description of the cyclotron targets properties, especially physicochemical characterization of irradiated elements. The second part is devoted to description of the electrodeposition procedures leading to obtain elements or their alloys coatings (e.g., nickel, uranium) as the targets for cyclotron and reactor generation of the radioisotopes. This review provides an evaluation of the role ILs can have in the production of isotopes.

Nano-radiogold-decorated composite bioparticles.

Hybrid composite bioparticles modified with stable and radioactive gold nanoparticles were prepared via reduction of tetrachloroauric acid within Lactobacillus rhamnosus cells. The resulting biocomposite material was characterized using a number of physicochemical techniques, including microscopic, spectroscopic and thermal methods. The bacterial particles act as a type of template for gold deposition. Gold nanoparticles of approximately 3.7 nm diameter are formed and are uniformly distributed within the bacterial cell, including its hydrogel outer shell. For radioactive gold-198, the ß- radiation emitted from the biocomposite particles can be used for therapeutic purposes, as demonstrated in vitro in cancer cell cultures. The antitumor activity can be further enhanced by incorporation of doxorubicin, a cytostatic drug, within composite particles. The cell viability data indicate the considerable synergistic effect of ß- radiation and doxorubicin on breast cancer cells (MCF-7). The antitumor action of the biocomposite particles is very promising for new anticancer therapies.

Redox interactions of technetium with neptunium in acid solutions.

Redox interaction of reduced technetium forms and technetium(VII) with neptunium(III), neptunium(IV) and neptunium(VI) have been investigated using electrochemical and spectroscopic (Vis-NIR) techniques. The neptunium species most stable in 4 M H2SO4, i.e. Np(IV) ions, do not reduce Tc(VII) in contrast to Np(VI) ions which oxidize Tc(IV) species to Tc(VII). The interaction of pertechnetates with Np(III) leads to formation of Tc(IV) species. The Vis-NIR measurements showed the generation of intermediate Tc(V) and Np(V) forms during the oxidation of Tc(IV) and competitive reduction of Np(VI). Tc(V) and Np(V) forms are characterised by the bands at 460 and 980 nm respectively.

Extraction of pertechnetates from HNO3 solutions into ionic liquids.

The extraction of pertechnetate ions from aquous solutions containing various concentrations of nitric acid into hydrophobic ionic liquids (ILs) has been examined at 25, 50 and 70 °C. The results show that the distribution ratio of Tc (DTc) between both phases weakly depends on the temperature and HNO3 concentration when IL's with relatively short aliphatic chains are used. The DTc obtained for all examined ILs, except methyltrioctylammonium bis(trifluoromethylsulfonyl)imide and 1-butyl-3-methylimidasolium hexafluorophosphate, are lower than 1.5. In the case of methyltrioctylammonium bis(trifluoromethylsulfonyl)imide a decrease of Tc concentration in aqueous solutions facilitates pertechnetate extraction into the organic phase.

Indirect Spin-Spin Coupling Constants in the Hydrogen Isotopologues.

The results of experimental and theoretical studies of indirect spin-spin coupling constants for hydrogen deuteride (HD), hydrogen tritide (HT), and deuterium tritide (DT) are described. The reduced coupling constants obtained from the gas-phase NMR (nuclear magnetic resonance) experiment conducted at 300 K are 2.338(1), 2.334(3), and 2.316(1) × 10(20) T(2) J(-1), while the ab initio values computed at the full configuration interaction level of theory equal 2.349(3), 2.343(3), and 2.322(3) × 10(20) T(2) J(-1) for HD, HT, and DT, respectively. The agreement of the experimental and theoretical results is improved when proper treatment of the influence of nuclear relaxation on the NMR spectrum is applied. However, there is a minor discrepancy between experiment and theory, exceeding the estimated error bars; potential sources of this discrepancy are discussed.

Dipyrrolonaphthyridinediones--structurally unique cross-conjugated dyes.

Red-emissive dyes based on a previously unknown skeleton--dipyrrolo[1,2-b:1',2'-g][2,6]naphthyridine-5,11-dione--can be easily synthesized from simple and inexpensive reagents by one- or two-step routes. A careful selection of the substituents gives access to a variety of dipyrrolonaphthyridinedione derivatives with intense fluorescence in the range of 520-740 nm.

Extraction of moderate oxidation state technetium species between 30 % tri-n-butyl phosphate and H2SO4/HNO3.

The extraction of technetium species at oxidation state lower than +7 has been examined in sulfuric and sulfuric/nitric acid solutions using UV-Vis spectroscopy and optically transparent thin layer cell (RVC-OTTLE). Soluble Tc(III), TcO2+ and [Tc2O2]3+ species with absorption bands at 420-450, 400, and 502 nm, respectively, were detected as products of pertechnetates electroreduction. The distribution ratios of 99Tc with lower than +VII oxidation state ionic species between 4 M H2SO4 and 30 % TBP/kerosene were found and are significantly lower than for TcO4- in the same solution.

Extension of Pyrrolopyrrole π-System: Approach to Constructing Hexacyclic Nitrogen-Containing Aromatic Systems.

A facile three-step approach to synthesizing quinoline-fused pyrrolopyrroles is reported. The crucial step in this synthesis is the condensation of 2-aminophenyl substituted pyrrolopyrroles with aromatic aldehydes. The resulting hexacyclic ladder-type dyes strongly absorb UV radiation and exhibit fluorescence at 450-510 nm. The presence of pyridine-type and pyrrole-type nitrogen atoms is important for the electronic properties of this almost planar heterocycle. These heteroatoms, along with the addition of moderate electron-withdrawing and electron-accepting substituents, provide a means for fine-tuning of the emission characteristics of the polycyclic conjugates.

Strong two-photon absorption enhancement in a unique bis-porphyrin bearing a diketopyrrolopyrrole unit.

A π-extended bis-porphyrin bridged via a diketopyrrolopyrrole unit was prepared in 5 steps. This fully conjugated π-system displays strongly distorted linear absorption, while its two-photon absorption cross-section reaches 2500-3000 GM at 940 nm. LC-like behaviour, easy orientation and low viscosity are, according to XRD, POM and DSC measurements, due to formation of plastic rather than a liquid crystal.

Photoinduced electron transfer in an amine-corrole-perylene bisimide assembly: charge separation over terminal components favoured by solvent polarity.

An assembly has been synthesised that consists of four units: a meso-substituted corrole (C3), perylene bisimide (PI), and two electron-rich triphenylamine (DPA) units. PI is connected through a 1,4-phenylene bridge to C3, whereas the two DPA units are linked to C3 through a diphenyl ether linkage, which is used for the first time to connect the various moieties. Various synthetic strategies were elaborated, and the chosen one afforded the final system in six steps in an overall yield of 6 %. The resulting assembly, made of three different units, was named a "triad". Excitation of the corrole (C3) or perylene bisimide (PI) units led to the charge-separated state DPA-C3(+)-PI(-) with a rate k>10(11) s(-1) in benzonitrile and dichloromethane (CH(2) Cl(2) ) or with k of the order of 10(10) s(-1) in toluene. The latter charge-separated state decayed to the ground state with a rate k=1.8×10(9) s(-1) in toluene. In the polar solvents benzonitrile and dichloromethane, recombination to the ground state competes with a charge shift to form the distal charge-separated state, DPA(+)-C3-PI(-), the formation of which occurs with a yield of 50 %. Recombination to the ground state of DPA(+)-C3-PI(-) occurs with a rate k=5×10(7) s(-1) in CH(2)Cl(2) and k=2×10(7) s(-1) in benzonitrile.