Publikationen

Synthetic quorum-sensing systems in mammalian cells has enabled the implementation of time- and distance-dependent bioprocesses, as well as the design of synthetic ecosystems emulating clinically important host–parasite interactions. In this chapter, we provide a detailed protocol of the design of a mammalian cell-to-cell signaling device and its integration into a mammalian quorum-sensing system for cell density-induced expression product genes. Cell-to-cell signaling is based on a sender cell, metabolically engineered for expression of alcohol dehydrogenase converting ethanol into acetaldehyde, and a receiver cell line for the dose-dependent translation of the acetaldehyde concentration into transgene expression by an acetaldehyde-responsive promoter. This protocol can be adapted easily to various cell types and transgenes for the design of versatile mammalian cell-based quorum-sensing systems. © 2011, Springer Science+Business Media, LLC.

Synthetic Biology aims at the design and construction of biologic systems with desired features by applying a modular strategy. This approach was used to investigate the interaction of multiple organisms in synthetic ecosystems.

The influence of the inhibitor particle size (nano and micro cerium dioxide) embedded in several hybrid sol-gel coating systems for the corrosion protection of aluminium AA2024 alloy was studied, as well as the influence of other parameters like the inhibitor loading level and the method of reticulation. The properties of the obtained coatings were evaluated by means of transmission electron microscopy, accelerated salt spray test and electrochemical impedance spectroscopy. All the varied parameters proved to have an important influence on the corrosion mechanism, and an improvement induced by the use of nanometric inhibitors in comparison with the micrometric ones was demonstrated. In the case of the strong reticulated matrix, an inhomogeneous dispersion of the inhibiting species (micro inhibitor) favours the tension formation, making the coating more vulnerable to the corrosion attack. For the same doping level it was observed that the reticulation with 1-methylimidazole (MI) leads to a slightly better corrosion protection. Concomitantly, it was shown that high loadings with inhibitors have an adverse effect on the corrosion protection.

Abstract LiAlH4 and AlCl3 reacted in a ratio 1:3 to obtain Cl2AlH, which is stabilised by the addition of two equivalents of N-methylpiperidine (nmp) to form dichloroalane (1) as bis adduct of nmp. Compound 1 was allowed to react with 2,6-tBu-4-MeC6H2OH and HOcHex in a 1:1 ratio to get compounds 2 and 3, respectively. Cl2Al(2,6-tBu-4-MeC6H2O)(nmp) (2) is a monomer in which the central aluminium atom is tetracoordinate. Contrary to the parent compound 1, compound 2 is stabilised by only one nmp molecule. The larger bulk of the alkoxide in 2 prevents the second nmp molecule to reach the aluminium atom. Compound 3 crystallises as unique anionic tri-nuclear aluminium entity [Al3Cl6(OR)4]– [nmp2H]+ with a protonated nmp as countercation. The lesser bulk of the cyclohexanolate leads to a higher oligomerisation of ROAlCl2 (R = cyclohexyl). When a relatively bulkier alcohol, 1-methylcyclohexanol, was allowed to react with mixtures of LiAlH4 and AlCl3 prepared in 1:1 and 1:3 ratios in solution, compounds 4 and 5, respectively, were obtained. Both compounds ((HClAlOR)2 (4) and (Cl2AlOR)2 (5), R = cHexMe-1)) are dimers with oxygen as bridging atom in the Al2O2 rings. All compounds 2, 3, 4, and 5 were structurally characterised by X-ray diffraction on single crystals.

A new type of precursor has been developed by molecular design and synthesised to produce tin doped indium oxide (ITO). The precursor consists of a newly developed bimetallic indium tin alkoxide, Me2In(OtBu)3Sn (Me = CH3, OtBu = OC(CH3)3), which is in equilibrium with an excess of Me2In(OtBu). This quasi single-source precursor is applied in a sol-gel process to produce powders and coatings of ITO using a one-step heat treatment process under an inert atmosphere. The main advantage of this system is the simple heat treatment that leads to the disproportionation of the bivalent Sn(II) precursor into Sn(IV) and metallic tin, resulting in an overall reduced state of the metal in the final tin doped indium oxide (ITO) material, hence avoiding the usually necessary reduction step. Solid state 119Sn-NMR measurements of powder samples confirm the appearance of Sn(II) in an amorphous gel state and of metallic tin after annealing under nitrogen. The corresponding preparation of ITO coatings by spin coating on glass leads to transparent conductive layers with a high transmittance of visible light and a low electrical resistivity without the necessity of a reduction step.

A novel hybrid sol-gel coating has recently been introduced as an alternative to high toxic chromate-based corrosion protection systems. In this paper, we propose a multiscale computational model to estimate the amount and time scale of inhibitor release of the active corrosion protection coating. Moreover, we study the release rate under the influence of parameters such as porosity and viscosity, which have recently been implicated in the stability of the coating. Numerical simulations obtained with the model predicted experimental release tests and recent findings on the compromise between inhibitor concentration and the stability of the coating.

Hydroxyapatite (HA) is one of the most widely used biomaterials for reconstructing skeleton. HA is mostly used in small devices that bear low mechanical load as well as in coatings since bulk HA-materials generally have poor mechanical properties. A significant effort has been spent towards reinforcing HA matrices with a variety of biocompatible elements and compounds. This study presents the experimental results of mechanical reinforcement of HA originated from biological materials (bovine femur bone, BHA) with nano-yttrium oxide (Y2O3, Sigma Aldrich™, particle size < 50 nm, purity > 99%). BHA-x wt% Y2O3 (x=5 and 10) powder blends were milled for 4 h in a planetary ball-mill with a 7:1 ball-to-powder weight ratio, using ZrO2 milling vials and balls. The milled powder blends were consolidated via cold-pressing (350 MPa) and sintering at different temperatures (1000-1300 °C) for 4 h under air atmosphere. For comparison purposes, similarly produced composites with commercial synthetic HA (CSHA) were also tested. The experimental results of density measurements and SEM observations for both BHA-composites and CSHA-composites showed that sintering satisfactorily occurred at 1300 °C. XRD analyses showed that the reinforcing oxides stabilize the lattice of HA against transformation to tri-calcium phosphate (TCP) even at 1300 °C. However, CSHA was more prone to form glassy phase after sintering at 1300 °C than BHA in the presence of the reinforcing oxides. The highest values of microhardness and compression strength were observed in the samples sintered at 1300 °C. BHA-composites have better mechanical properties than CSHA-composites. In particular, BHA-composites have higher compression strength (for 5 wt% Y2O3 reinforcement, 101.79 MPa) than CSHA (75.81 MPa). Similar results were obtained for 10 wt% Y2O3 reinforcement. However, the best behavior is shown for 10 wt% Y2O3 than 5 wt%. Probably, 10 wt% exceeds the capacity of HA lattice to accommodate the yttrium ions. The extensive formation of glassy phase in the CSHA-composites sintered at 1300 °C (443.57 HV for 5 wt% Y2O3) resulted in harder materials than the BHA-composites sintered at the same temperatures (330.2 HV for 5 wt% Y2O3). Nevertheless, hard biomaterials ruin rapidly the tissues around the implant. Consequently, the experimental results, in conjunction with the important role of Y2O3 in bone forming and healing mechanism, qualify the produced BHA-composites for further in vitro and in vivo studies.