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We report the layer-by-layer (LbL) surface functionalization of high aspect ratio (>100000:1) polystyrene (PS) electrospun fibers (ESFs) of various diameters (400 nm or 1.5 µm) with polyelectrolytes (PEs), deoxyribonucleic acid (DNA) oligonucleotides, and PE/gold nanoparticle (Au NP ) composite layers. ESFs were coated with poly(allylamine hydrochloride) (PAH) and poly(styrenesulfonate) (PSS) multilayers, the thickness of which was controlled by adjusting the number of PE layers deposited. PAH/PSS multilayer buildup was demonstrated by dissolving the inner PS fibers with tetrahydrofuran, resulting in the formation of hollow PAH/PSS fibers. DNA multilayer coated ESFs were also prepared using oligonucleotides with repeating blocks of adenosine and guanosine (polyA 15 G 15 ) and thymidine and cytidine (polyT 15 C 15 ). The polyT 15 C 15 was labeled with tetramethylrhodamine. Linear DNA multilayer buildup on the ESFs was observed through an increase in fluorescence intensity using confocal laser scanning microscopy. Finally, nanocomposite PE/gold fibers were prepared by immersing the PAH/PSS-coated PS fibers into a dispersion of 4-(dimethylamino)pyridine-stabilized Au NP . This resulted in a dense packing of Au NP in the PE film localized on the PS fiber surface. These fibers have potential application in sensing, filtration, and catalysis and as release materials in medicine and agriculture.

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Electrospinning is a versatile method for the preparation of continuous fibers with diameters ranging from micrometers down to a few nanometers.[1] Nonwovens of electrospun fibers are obtained from polymer solution or melt when a materials jet moves from an electrode to the corresponding counter electrode under the influence of a strong electrical field (up to several kV cm -1 ) with simultaneous evaporation of solvent or solidification of melt. Although the experimental set-up is simple the process is complex since numerous parameters such as solution viscosity, electrical conductivity, surface tension, polymer molecular mass, molecular mass distribution, glass transition, distance of electrodes, shape of electrodes, strength of electrical field, nature of counter electrode, processing atmosphere etc. influence shape, yield, and dimensions of resulting fibers. Nevertheless, electrospinning of polymers offers unique opportunities for the preparation of manifold fibers since nearly every soluble or meltable polymer can be processed to fibers of different shapes, dimensions, and surface characteristics and composites can be prepared simply by addition of a composite component to the electrospinning solution. Thereby, composite fibers, functional fiber, and fibers with complex structure can be prepared by electrospinning of polymers with additional compounds like nanoparticles, carbon nanotubes, catalysts, and enzymes just to name a few. [2][3][4][5] Recently, dispersions of M13 viruses in watersoluble polyvinylpyrrolidon were processed to nanofibers by electrospinning. It was clearly shown that virus infection of bacterial host was possible by viruses coming form the electrospun virus-based nonwovens. [6] In another pioneering work Zussman et al. showed encapsulation of Escherichia (E.) coli and Staphylococcus albus by elctrospinning of bacteria suspensions with poly(vinyl alcohol) (PVA). [7] These remarkable findings clearly showed that nonwovens composed of polymer nanofibers and complex biological objects can be prepared directly without total loss of biological functionality. In extension of these encouraging results we have undertaken attempts to electrospin bacterial aqueous dispersions with water-soluble poly(ethylene oxide) and to compare survival rates of different bacteria at ambient temperatures.[8] Bacteria-modified nonwovens furnished with tailored complex biological functionalities such as virus or bacteria could be of great interest as novel biohybrid materials. These new biohybrid materials could be of interest as living membranes for a variety of application areas like filtration, separation membranes, sensors, catalysis, textiles etc. The removal of water by rapid evaporation upon electrospinning is anticipated to cause a drastic change of the bacterial osmotic environment. For our experiments we therefore chose a bacterium known to be adapted to life at low water activities and to survive rapid changes in osmotic pressure. Such an organism is Micrococcus (M.) luteus, which is an airborne non-path...