Study of Electroless Copper Deposition on Fe Powder

The electrolytic deposition of an electropositive metal is often accompanied by electroless deposition. However, this process is very difficult to control. For that reason, our study has been aimed at the conditions of the electroless deposition of copper coating onto the iron powder particles from sulphate electrolyte. The process consists of two partial reactions; solid iron substrate dissolves into the solution, thus providing the electrons necessary for reduction of copper. The course of the electroless process depends to a large extent on the composition and pH of the electrolyte as well as on the size and concentration of the iron powder particles in the electrolyte. In order to suppress the spontaneous electroless deposition of copper, sodium citrate as complexing agent was used. The following parameters were determined to characterize the reaction course: the heterogeneous rate constant of Fe powder dissolution and degree of Fe conversion as well as thickness of the Cu layer on the Fe powder, both of the latter evaluated upon attaining the stationary state. The main influence exhibited on the reaction course is the efficient surface area available for electroless deposition.     

Carbonic anhydrase inhibitors: design of membrane-impermeant copper(II) complexes of DTPA-, DOTA-, and TETA-tailed sulfonamides targeting the tumor-associated transmembrane isoform IX

The synthesis and carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of two series of aromatic sulfonamides and their Cu(II) derivatives, incorporating metal-complexing moieties of the DTPA, DOTA, and TETA type are reported. The new compounds were designed in such a way as to possess high affinity for Cu(II) ions, exploiting four pendant carboxylate moieties in the DTPA derivatives, as well as the cyclen/cyclam macrocyles, and three pendant acetate moieties in the DOTA and TETA derivatives. The new derivatives showed modest inhibition of the cytosolic isoform CA I (K(I) values in the range of 66-2130 nM), were better CA II inhibitors (K(I) values in the range of 21-360 nM), and excellent inhibitors of the tumor-associated isoform CA IX (K(I) values in the range of 4.1-110 nM), with selectivity ratios for the inhibition of the tumor (CA IX) over the cytosolic (CA II) isozyme in the range of 10.74-20.88 for the best derivatives. Copper complexes were more inhibitory than the corresponding ligand sulfonamides, and showed membrane impermeability, thus, having the possibility to specifically target the transmembrane CA IX that has an extracellular active site. Incorporation of radioactive copper isotopes in this type of CA inhibitor may lead to interesting diagnostic/therapeutic applications for such compounds.     

Generation of carrier peptides for the delivery of nucleic acid drugs in primary cells

Now that the human genome has been decoded, the demand for novel therapeutic concepts, such as gene and stem cell therapy, is higher than ever before. Although new and better pharmaceutical agents are available, their efficient delivery to the intracellular site of action is still a serious challenge. A possible solution to this problem is the use of cell-penetrating peptides as delivery vectors, including derivatives of human calcitonin (hCT). The aim of this study was to synthesise novel branched hCT-derived peptides for the noncovalent delivery of nucleic acids. The uptake of the resulting oligocationic peptides into various cell lines as well as primary cells was monitored by fluorescence microscopy. To determine the appropriate peptide-plasmid charge ratios for efficient cell transfection, electromobility shift assays were carried out. Finally, flow cytometric and fluorescence microscopic studies of gene expression highlighted two novel hCT-derived peptides as highly effective in the delivery of noncovalently complexed plasmid DNA. Thus, the absence of cytotoxicity paired with highly efficient cell internalisation and transfection rates, in primary cells as well, make both peptides powerful candidates as drug delivery vectors, especially for plasmid DNA, for both in vivo and ex vivo therapeutic applications.     

A potent integrin antagonist from a small library of cyclic RGD pentapeptide mimics including benzyl-substituted azabicycloalkane amino acids

A small library of cyclic RGD pentapeptide mimics, including benzyl-substituted azabicycloalkane amino acids, was synthesized with the aim of developing active and selective integrin antagonists. In vitro binding assays established one particular compound with affinity for both the alpha(v)beta(3) and the alpha(v)beta(5) integrins. The synthesis in solution and the in vitro screening of these RGD derivatives, as well as the determination of the conformational properties of the integrin ligands by spectroscopic and computational methods are described.     

High‐density polyethylene reinforced with submicron titania particles

Submicron titania particles were prepared by means of two different synthetic procedures in order to obtain different particle size (diameter ranging from 20 to 350 nm), shapes, and morphologies (amorphous or crystalline). Titania particles were surface modified with octadecylsilane in order to improve their compatibility with respect to polymeric matrices. High‐density polyethylene (HDPE)–titania composites were prepared by melt blending by using an internal mixer. The obtained composites were mechanically characterized in quasi static and creep tensile conditions. The presence of submicron titania particles (1 %vol) led to a significant increase of elastic modulus (20–25%) with respect to the unreinforced HDPE together with a slight increase of yield stress and a decrease of ultimate elongation. An interesting reduction for both elastic and viscoelastic creep compliance components was also evidenced. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

LLDPE with Exclusively Ethyl Branches by Tandem Catalysis with Single-Site Zr(IV)/Co(II) Catalysts

Semicrystalline linear low density polyethylenes (LLDPEs) with exclusively ethyl branching (from 7 to 56 branches per 1,000 carbon atoms) were prepared from ethylene by homogeneous tandem catalytic systems comprising (imino)pyridine cobalt(II) dichlorides as oligomerization precursors, bis(cyclopentadienyl)zirconium(IV) dichloride as copolymerization precursor and methyaluminoxane as activator. The activity of the tandem systems was evaluated by varying either the molar fraction of the cobalt precursors or the ethylene pressure. The latter parameter was of crucial importance to control both the productivity and the extent of 1-butene incorporation. In particular, increasing the ethylene pressure from 2 bar to 4 bar changed the “comonomer effect” from positive to negative.     

All-conjugated block copolymers

All-conjugated block copolymers of the rod-rod type came into the focus of interest because of their unique and attractive combination of nanostructure formation and electronic activity. Potential applications in a next generation of organic polymer materials for photovoltaic devices ("bulk heterojunction"-type solar cells) or (bio)sensors have been proposed. Combining the fascinating self-assembly properties of block copolymers with the active electronic and/or optical function of conjugated polymers in all-conjugated block copolymers is, therefore, a very challenging goal of synthetic polymer chemistry. First examples of such all-conjugated block copolymers from a couple of research groups all over the world demonstrate possible synthetic approaches and the rich application potential in electronic devices. A crucial point in such a development of novel polymer materials is a rational control over their nanostructure formation. All-conjugated di- or triblock copolymers may allow for an organization of the copolymer materials into large-area ordered arrays with a length scale of nanostructure formation of the order of the exciton diffusion length of organic semiconductors (typically ca. 10 nm). Especially for amphiphilic, all-conjugated copolymers the formation of well-defined supramolecular structures (vesicles) has been observed. However, intense further research is necessary toward tailor-made, all-conjugated block copolymers for specific applications. The search for optimized block copolymer materials should consider the electronic as well as the morphological (self-assembly) properties.     

Electrocombustion of humic acid and removal of algae from aqueous solutions

This paper reports experiments involving the electrochemical combustion of humic acid (HA) and removal of algae from pond water. An electrochemical flow reactor with a boron-doped diamond film anode was used and constant current experiments were conducted in batch recirculation mode. The mass transfer characteristics of the electrochemical device were determined by voltammetric experiments in the potential region of water stability, followed by a controlled current experiment in the potential region of oxygen evolution. The average mass transfer coefficient was 5.2 × 10⁻⁵ m s⁻¹. The pond water was then processed to remove HA and algae in the conditions in which the reaction combustion occurred under mass transfer control. To this end, the mass transfer coefficient was used to estimate the initial limiting current density applied in the electrolytic experiments. As expected, all the parameters analyzed here—solution absorbance at 270 nm, total phenol concentration and total organic carbon concentration—decayed according to first-order kinetics. Since the diamond film anode successfully incinerated organic matter, the electrochemical system proved to be predictable and programmable.     

In situ FTIR spectroelectrochemistry of poly[2-(3-thienyl)ethyl acetate] and its hydrolyzed derivatives

Poly[2-(3-thienyl)ethyl acetate] (PTEtAc) was chemically synthesized and transformed to partially hydrolyzed PTEtAc (PTEtAcOH) and poly[2-(3-thienyl)ethanol] (PTEtOH). The influence of the acetoxy and hydroxyl terminal functionalities in the side groups on the electrochemical properties of these polyalkylthiophenes was studied by cyclic voltammetry and in situ FTIR spectroelectrochemistry. The cyclic voltammograms point to a chemically reversible behaviour of the p-doping process for PTEtAc and PTEtAcOH, while for PTEtOH the redox activity of the polymer film is lost during consecutive potential scans.The attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used to investigate the p-doping of the three different type of thiophene polymer films. In situ FTIR spectra taken at different electrode potentials in a cyclovoltammetric scan display the doping induced changes of the polymer pattern. Important differences in the behaviour of the polymers were observed and interpreted in terms of different film structures.     

Functionalization of Si(1 0 0) with ferrocene derivatives via “click” chemistry

We prepared ferrocene-modified silicon surfaces through a three-step procedure consisting of the photochemical anchoring of 11-bromo-1-undecene on H-Si(1 0 0), followed by treatment with NaN₃ and by a reaction with ethynylferrocene via azide-alkyne Huisgen cycloaddition reaction, also known as “click” chemistry. The advantages of this approach are multiple: the synthetic approach is flexible, provided a CC tethering arm is present on the molecule of interest; a self-assembled hydrocarbon chain can guarantee a good coverage and resistance to the further synthetic steps; the redox centers are located at the outer surface, where a good contact with the electrolyte becomes possible. We have monitored the progression of the reaction steps by XPS, and characterized the resulting new hybrid on Si by electrochemical methods. The presence and chemical nature of the redox species covalently attached to the SAM on Si has been evaluated by XPS, while the overall coverage has been calculated by CV measurements. A reversible electrochemical response has been evidenced for the hybrids and the progressive ageing followed at thousands of oxidation-reduction cycles.