Scientific publications

The paper reports first on the electrochemical behavior in liquid Li+ electrolytes of 200 nm thick single sol-gel (CeO2)0.81-TiO2 electrochromic (EC) layers deposited by the dip-coating process. The electrolytes were solutions of 1 M LiCO4 dissolved in dry propylene carbonate (PC) (containing 0.03wt% of water) and wet PC containing up to 10wt% of water, respectively. Then an electrochemical quartz crystal microbalance was used as a sensitive detector to analyze the mass changes occurring during the Li+ ion exchange processes. These electrochemical processes were studied for 370 nm thick double layers, deposited on gold-coated quartz crystal electrodes and sintered at 450 °C in air. The electrolytes were the same solutions with water content varying from 0.03 up to 3wt% of water. The processes have been studied in the potential range from -2.0 to + 1.0 V vs. Ag/AgClO4 during 100 voltammetry cycles. The composition of the (CeO2)0.81-TiO2 layers was found to change during the early cycles, mainly because of an irreversible Li+ intercalation. It was found, however, that the mass change observed during cycling is not due only to a pure Li+ ion exchange process but also involves the adsorption/desorption or exchange of other cations and anions contained in the electrolyte. These ions are Li+ and ClO4- in dry electrolyte and Li+, hydrated Li(H2O)n+ and ClO4- in wet electrolyte. The improvement of the reversibility of the intercalation and deintercalation processes as well as the faster kinetics observed in wet electrolytes are finally discussed in terms of a model in which the formation of hydrated Li+ ions takes an important role.

The reaction of the oligoalumosiloxane [Ph2SiO]8[AlO(OH)]4 (1) with hexamethyldisilazane leads to the triple ionic [Ph2SiO]8[AlO2]2[AlO(O-SiMe3)]2[NH4-THF]2∙2 THF (2) and in the presence of pyridine to [Ph2SiO]8[AlO1.5]4∙2py∙1.5 C7H8 (3). Apart from the usual characterization techniques (NMR and IR spectroscopy) the molecular structures of 2 and 3 have been determined by single-X-ray diffraction analyses. Both alumosiloxanes 2 and 3 present new types of molecular structures with a central four membered Al2O2-ring, on which the further aluminium atoms are attached via oxygen atoms. This leads to an Al4-lozenge, which is centered in subtriangles by oxygen atoms.

Treatment of polymethyl methacrylate with dodecylamine and diethylenetriamine produces a chemornechanical polymer, which undergoes large macroscopic motions as a result of selective recognition of substrates (effectors) in the surrounding aqueous solution. The kinetics of these fully reversible expansions and contractions are compared to those of effector absorption and desorption. The expansion correlates with a polymer particle weight increase, which is in turn found to be largely a function of the uptake of water necessary for solvation of the effector molecules. The selectivity of the motions depends on the nature and placement of the effector ionic sites, and also on the size and nature of the organic residues. Ion pairing between the protonated amine functions and inorganic anions or anionic groups of organic effectors plays a decisive role. The large effects seen with aromatic effectors such as nucleotides, in contrast with saturated analogues, point to cation-pi and C-H-pi interactions as essential elements for the distinction between different effectors, including isomeric compounds. The material exhibits symmetric expansion/pH profiles, which depend distinctly on the ionic strength of the solution. The strong dependence of the motions not only on the applied pH, but also on the concentrations of two simultaneously active effectors, such as AMP and phosphate, present chemically induced logical gate functions; this is tentatively explained by a two-site binding model. In contrast, the large expansions produced by simultaneous action of, for example, copper or zinc and amino acids or peptides are due to co-complexation between the metal ions and known organic chelators. With such ternary complexes, volume expansions by factors of up to 15 are possible with effector concentrations as low as 0.25 mm. The sensitivity can be further increased by miniaturization of the polymer particles; the velocity of the response can be optimized by increasing the surface-to-volume ratio. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The straightforward production and dose-controlled administration of protein therapeutics remain major challenges for the biopharmaceutical manufacturing and gene therapy communities. Transgenes linked to HIV-1-derived vpr and pol-based protease cleavage (PC) sequences were co-produced as chimeric fusion proteins in a lentivirus production setting, encapsidated and processed to fusion peptide-free native protein in pseudotyped lentivirions for intracellular delivery and therapeutic action in target cells. Devoid of viral genome sequences, protein-transducing nanoparticles (PTNs) enabled transient and dose-dependent delivery of therapeutic proteins at functional quantities into a variety of mammalian cells in the absence of host chromosome modifications. PTNs delivering Manihot esculenta linamarase into rodent or human, tumor cell lines and spheroids mediated hydrolysis of the innocuous natural prodrug linamarin to cyanide and resulted in efficient cell killing. Following linamarin injection into nude mice, linamarase-transducing nanoparticles impacted solid tumor development through the bystander effect of cyanide. © The Author 2006. Published by Oxford University Press. All rights reserved.

Pharmacologic transgene-expression dosing is considered essential for future gene therapy scenarios. Genetic interventions require precise transcription or translation fine-tuning of therapeutic transgenes to enable their titration into the therapeutic window, to adapt them to daily changing dosing regimes of the patient, to integrate them seamlessly into the patient's transcriptome orchestra, and to terminate their expression after successful therapy. In recent years, decisive progress has been achieved in designing high-precision trigger-inducible mammalian transgene control modalities responsive to clinically licensed and inert heterologous molecules or to endogenous physiologic signals. Availability of a portfolio of compatible transcription control systems has enabled assembly of higher-order control circuitries providing simultaneous or independent control of several transgenes and the design of (semi-)synthetic gene networks, which emulate digital expression switches, regulatory transcription cascades, epigenetic expression imprinting, and cellular transcription memories. This review provides an overview of cutting-edge developments in transgene control systems, of the design of synthetic gene networks, and of the delivery of such systems for the prototype treatment of prominent human disease phenotypes. Copyright © 2006 John Wiley & Sons, Ltd.

Nutrient and oxygen availability are key metabolic parameters for biopharmaceutical manufacturing. In order to enable mammalian cells to manifest their intracellular nutrient and oxygen levels we engineered a genetic sensor circuitry which converts signals impinging on the cellular redox balance into a robust reporter gene expression readout. Capitalizing on the Streptomyces coelicolor redox control system, consisting of REX modulating ROP-containing promoters in an NADH-dependent manner, we designed a mammalian dual sensor transcription control system by fusing REX to the generic VP16 transactivation domain of Herpes simplex, which reconstitutes an artificial transactivator (REDOX) able to bind and activate chimeric promoters assembled by placing a ROP operator module 5′ of a minimal eukaryotic promoter (PROP). When nutrient levels were low and resulted in depleted NADH pools REDOX-dependent PROP-driven expression of secreted (human-secreted alkaline phosphatase; SEAP) or intracellular (Renilla reniformis luciferase; rLUC) reporter genes was high as a consequence of increased REDOX-PROP affinity. Conversely, at hypoxic conditions leading to high intracellular NADH levels, strongly reduced REDOX-PROP interaction mediated low-level transgene expression in Chinese hamster ovary (CHO-K1) cells. Other molecules (for example, 2,4-dinitrophenol, cyanide or hydrogen peroxide) which are known to imbalance the intracellular NADH/NAD+ poise could also be detected using the REDOX-PROP sensor circuitry. REDOX's sensor capacity (nutrient and oxygen levels) operated seamlessly in transgenic CHO-K1 cell derivatives adapted for growth in serum-free suspension cultures and enabled precise monitoring of the population's metabolic state. As the first genetic metabolic sensor designed for mammalian cells, REDOX may foster advances in process development and biopharmaceutical manufacturing. © 2006 Elsevier Inc. All rights reserved.

With a rate exceeding 90% in cattle, artificial insemination (AI) is the prime reproduction technology in stock farming. AI success is expected to increase with extended persistence of sperms in utero. In order to enable controlled sperm release during artificial insemination we have designed two strategies for the automated microencapsulation of bovine spermatozoa in either alginate-Ca2+ or cellulose sulfate (CS)-poly-diallyldimethyl ammonium chloride (pDADMAC) capsules using standard encapsulation hardware. Animal protein- and citric acid-free sperm extenders and encapsulation protocols have been developed to ensure encapsulation compatible with sperm physiology. Bovine spermatozoa have showed high motility rates inside CS-pDADMAC-based capsules, were preserved by standard cryoconservation and rescued with high viability/motility following disintegration of the thawed capsules. CS-pDADMAC-based capsules break up within 72 h after addition of either purified cellulase or cellulase-filled alignate-Ca2+ capsules. The controlled release, associated with the microencapsulation of bovine spermatozoa, may be a promising approach to increase the success rate of artificial insemination. © 2005 Elsevier B.V. All rights reserved.

Five new derivatives of the polycyclic alumosiloxalic [Ph2SiO]8[Al(O)OH]4 have been synthesized by replacement of the protic hydrogen atoms on the hydroxy-groups attached to the aluminium atoms by the divalent group 14 elements germanium, till and lead. The compounds can be divided in those with one metal atom per alumosiloxane moiety, [Ph2SiO]8[Al(O)OH]2[AlO2]M (M=Ge, Sn), and those with complete substitution of the protic hydrogen atoms by metal atoms like [Ph2SiO]8[AlO2]4M2 (M= Sn, Pb). Always one element of the series Ge, Sn, Ph is missing in the two types of compounds. Crystal structure analyses of [Ph2SiO]8[Al(O)OH]2[AlO2]2M∙2 C4H8O2 (M= Ge (1), Sn (2a)), [Ph2SiO]8[Al(O)OH]2[AlO2]2Sn∙2THF(2b) and [Ph2SiO]8[AlO2]4M2 (M= Sn (3) Pb (4)) have been performed elucidating either polycyclic basket-type (1, 2a, 2b) or closed polyhedral structures (3, 4).