Tannic acid (TA) was assembled in alternation with two different polycations, strong poly(dimethyldiallylamide) (PDDA) and weak poly(allylamine) (PAH), using a layer-by-layer technique. Their deposition at different pH was confirmed by QCM, UV−vis spectroscopy, and surface charge measurements. TA/polyelectrolyte multilayer films and capsules have pH-dependent structural properties different from those of commonly used poly(styrenesulfonate)/poly(allylamine) (PSS/PAH) compositions. The lowest speed of TA/polycation multilayer dissolution was found at the conditions close to those used for film preparation. Permeability for fluorescein-labeled dextrans into tannic acid/polycation capsules with a five bilayer wall composition was investigated as a function of pH using confocal microscopy. It was found that minimal permeability occurs at pH 5−7 and maximal permeability at very high and very low pH, providing new opportunities for capsule loading as compared with an established procedure for PSS/PAH microcapsules. For TA/PDDA layers, less soluble films and less permeable capsules were obtained as compared with TA/PAH layers.

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Stable, super-hydrophilic (water contact angle approximately equal to 0 degrees) titanium dioxide nanoparticle thin films have been obtained on substrates with different initial wettability such as glass, poly(methyl methacrylate) and poly(dimethyl siloxane) using layer-by-layer nano-assembly method. Titanium dioxide nanoparticles were alternated with poly(styrene sulfonate) to form films of thickness ranging from 11 nm to 220 nm. The hydrophilicity of these thin films increases with increasing number of deposited PSS/TiO2 bilayers. It was found that 2, 5 and 20 layers were needed to form super-hydrophilic TiO2 coating on glass, PMMA and PDMS respectively. Oxygen plasma treatment of substrate surfaces enhanced the formation of homogeneous TiO2 films and accelerated the formation of hydrophilic layers. Super-hydrophilicity has been shown to be unique to PSS/TiO2 films as compared with other polyelectrolyte/nanoparticle layers, and UV irradiation may restore hydrophilicity even after months of storing of the samples. Biocompatibility of TiO2 nanoparticle films has been demonstrated by the successful cell culture of human dermal fibroblast.

The influence of a catalase (Cat) layer located at different depths in the layer-by-layer hemoglobin/polystyrene sulfonate films with an (Hb/PSS)(20)(-)(x)/(Cat/PSS)/(Hb/PSS)(x) (x = 0-20) architecture on kinetics of hemoglobin degradation under treatment with hydrogen peroxide solutions of different concentrations and features of H(2)O(2) decay in surrounding solutions has been studied. While assembled on the top of the multilayers, the catalase layer shows the highest activity in hydrogen peroxide decomposition. Hemoglobin in such films retains its nativity for a longer period of time. The effect of catalase layers is compared with that of protamine, horseradish peroxidase, and inactivated catalase. Positioning an active layer with catalytic properties as an outer layer is the best protection strategy for layer-by-layer assembled films in aggressive media.

Laminar‐flow microfabrication is shown to produce complex micrometer‐resolved polyelectrolyte micropatterns at ambient conditions (see Figure). This simple deposition procedure shows great versatility, with the capacity to fabricate micropatterns containing unstable and sensitive biological objects on the surface of any appropriate substrate.

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Freely suspended layer‐by‐layer nanomembranes have been transferred onto an array of circular openings of varying diameters (a gradient array). The mechanical behavior of these nanomembrane gradient arrays have been studied using both bulging tests and point‐load experiments. By using the gradient array, experimental statistics are significantly improved. The observed scale‐dependent mechanical properties, investigated in an efficient fashion, are evident in the trend of increasing elastic modulus with decreasing membrane diameter. The observed increase in bending rigidity with decreasing membrane diameter is satisfactorily described by the theoretical model of an elastic membrane under a point load.

We demonstrate that photobleaching can be significantly suppressed in fluorescentlabeled polyelectrolyte layer-by-layer (LbL) films by efficient spatial isolation of the dye molecules using multilayered architecture. The films exhibited excellent temporal stability under high excitation power where the bulk films suffered a significant photobleaching. Quenching of the fluorescence caused by the resonant energy transfer between the dye molecules and gold nanoparticles exhibited a weak distance dependence with significant quenching extending beyond 20 nm distance. The robust, freely suspended, fluorescent LbL films exhibited stable fluorescence response under deformation which can make them attractive for sensitive fluoroimmunoassays.