A unique combination of surface chemistry and self-assembly of amphiphilic block copolymers was employed to obtain-for the first time-solid-supported biomimetic polymer bilayers. An organized monolayer from sulfur-functionalized poly(butadiene)-b-poly(ethylene oxide) was covalently attached to ultrasmooth gold upon Langmuir-Blodgett transfer. Hydrophobic interactions, on the other hand, were exploited to attach the second monolayer. As a result, we obtained a homogeneous hydrophilichydrophobic-hydrophilic structure, similar to supported lipid bilayers by architecture, stability and fluidity. Our polymer bilayers, however, outperform such lipid membranes with regard to tunability of thickness and stability in gaseous environments. As characterized by surface analysis tools (AFM, SPR), solid-supported polymer membranes are smooth with a thickness of ca. 11 nm, resistant to rinsing with aqueous solutions and stable upon drying and rehydration. These properties could be attractive for nanotechnological applications, such as immobilization of functional molecules or nanoparticles, sensor development or preparation of chemically responsive functional surfaces.

An easy route to planar solid-supported polymer membranes by vesicle spreading is described. Pre-organized poly(butadiene)-block-poly(ethylene oxide)(PB-PEO) assemblies were spread on two different supports, i.e. strongly hydrophilic glass surfaces and ultrasmooth gold substrates. Polymer membranes were produced on a hydrophilic support by spreading hydroxyl-functionalized polymer vesicles, while covalently immobilized polymer membranes were obtained by spreading LA-functionalized polymer vesicles on gold substrates. Covalently bound membranes were further incubated with the peptide polymyxin B. Interactions with the polymer membrane were detected by EIS. These systems are of great interest to fundamental membrane science and have potential in technological applications, such as drug screening and (bio)sensing.

Tethered lipid membranes or immobilized lipid vesicles are frequently used as biomimetic systems. In this article, the authors presented a suitable method for efficient immobilization of lipid vesicles onto a broad range of surfaces, enabling analysis by quantitative methods even under rigid, mechanical conditions-bare surfaces such as hydrophilic glass surfaces as well as hydrophobic polymer slides or metal surfaces such as gold. The immobilization of vesicles was based on the electrostatic interaction of zwitterionic or negatively charged lipid vesicles with two types of cationic chemically modified bovine serum albumin ͑cBSA͒ blood plasma proteins ͑cBSA-113 and cBSA-147͒. Quantitative analysis of protein adsorption was performed as the cBSA coatings were characterized by atomic force microscopy, surface zeta potential measurement, fluorescence microscopy, and surface plasmon spectroscopy, revealing a maximal surface coverage 270-280 ng/ cm 2 for 0.02 mg/ml cBSA on gold. Small unilamellar vesicles as well as giant unilamellar vesicles ͑GUVs͒ were readily immobilized ͑ϳ15 min͒ on cBSA coated surfaces. GUVs with 5-10 mol% negatively charged 1,2,-dipalmitoyl-sn-glycero-3-phosphoglycerol remained stable in liquid for at least 5 weeks.

Whole cells are attractive biocatalysts, particularly if the reaction requires cofactors or involves multiple transformations. Immobilization of the catalyst is often a prerequisite for continuous processes. The highly cationic chemically modified plasma protein bovine serum albumin ͑cBSA-147͒ has been applied for the electrostatically mediated immobilization of the planktonic bacterium E. coli BL21 star (DE3), and the resulting biofilms were superior to those formed on poly-L-lysine coated surfaces. The biocatalyst was immobilized in a capillary column ͑inside diameter of 530 m and L =30 m͒ and evaluated in the enantioselective reduction of ethyl acetoacetate to R-͑-͒ethyl hydroxybutyrate. In continuous operation in the microreactor format, the productivity of the cells was about 30% higher than that determined in a bench-scale fermentation system. This increase is attributed to the improved mass transfer over short geometrical dimensions. The similarity in the results indicates that studies on a biofilm-coated microreactor can be used for the accelerated collection of data for process optimization.

No abstract