Layer-by-layer assembly of brushes of vertically-standing enzymatic nanotubes.

Brushes of vertically-standing enzyme-containing nanotubes are prepared onto planar surfaces by a combination of hard-templating and layer-by-layer assembly. The nanotubes have a core-shell morphology made of two compartments, one for mechanical rigidity, the other containing ß-lactamase for bioactivity. We demonstrate inclusion of the enzymatic component either in the core or in the shell part of the nanotubes. Kinetic studies reveal that both types of systems are bioactive but that the activity is significantly better preserved over long time periods when ß-lactamase is incorporated in the core of the nanotubes.

Uptake of Long Protein-Polyelectrolyte Nanotubes by Dendritic Cells.

Anisotropic nanostructures, such as nanotubes, incorporating bioactive molecules present interesting features for application as drug delivery carriers. Here, we present the synthesis of layer-by-layer (LbL) nanotubes including protein (ovalbumin) layers and go from simple to more complex synergetic combinations of synthetic and natural polyelectrolytes, leading to structures with tunable properties. The rigidity in organic and aqueous media, the stability in buffer solution and the uptake of different LbL tubes by dendritic cells (DCs) are analyzed to contrast size and chemistry. The most rigid studied systems appear as the best candidates to be internalized by cells, regardless of the chemistry of their outermost layers. The successful transport of long protein-loaded robust rigid nanotubes to the cytoplasm of DCs paves the way for their use as new cargo for the delivery of large amounts of antigen to such cells.

Early Stages of Antibacterial Damage of Metallic Nanoparticles by TEM and STEM-HAADF.

BACKGROUND: Propagation of pathogens has considered an important health care problem due to their resistance against conventional antibiotics. The recent challenge involves the design of functional alternatives such as nanomaterials, used as antibacterial agents. Early stages of antibacterial damage caused by metallic nanoparticles (NPs) were studied by Transmission Electron Microscopy (TEM) and combined Scanning Transmission Electron Microscopy with High Angle Annular Dark Field (STEM-HAADF), aiming to contribute to the elucidation of the primary antibacterial mechanism of metallic NPs. METHODS: We analyze the NPs morphology by TEM and their antibacterial activity (AA) with different amounts of Ag and Cu NPs. Cultured P. aeruginosa were interacted with both NPs and processed by TEM imaging to determine NPs adhesion into bacteria wall. Samples were analyzed by combined STEM-HAADF to determine the NPs penetration into bacterium and elemental mapping were done. RESULTS: Both NPs displays AA depending on NPs concentration. TEM images show NPs adhesion on bacterial cells, which produces morphological changes in the structure of the bacteria. STEM-HAADF also proves the NPs adhesion and penetration by intracellular localization, detecting Ag/Cu species analyzed by elemental mapping. Moreover, the relative amount of phosphorus (P) and sulfur (S) increases slightly in P. aeruginosa with the presence of NPs. These elements are associated with damaged proteins of the outer cell membrane. CONCLUSIONS: Combined microscopy analyses suggest that the early stages of antibacterial damage caused by alteration of bacterial cell wall, and can be considered a powerful tool aiming to understand the primary antibacterial mechanism of NPs.

Nanopapers of layer-by-layer nanotubes.

Mats of nanofibers are important as biological scaffolds, (bio)functional electrodes, or smart membranes. Herein, we show that layer-by-layer (LbL) assembly of a wide variety of compounds in nanoporous templates, followed by a straightforward filtration methodology of the nanotubes after membrane dissolution, leads to the fabrication of LbL nanopapers over centimeter square surfaces. The texture of the nanopapers can be easily tuned by varying the rigidity of the nanofibers, which can be achieved by changing their wall thickness, crosslinking them, or developing nanotubes with a core-shell structure. In the nanopapers, the tubes deform by different mechanisms, including flattening, twisting and scrolling, depending on tube rigidity. The possibility to manufacture multilayered nanopapers made of stacks of different nanofibers, or chemically post-functionalize them, is also demonstrated; in addition, the fabrication of enzymatically-active nanopapers is shown. Considering the vast range of materials which can be used for the construction of nanotubes including, e.g., proteins, polysaccharides, conducting polymers or nanoparticles, and the many possible post-functionalization techniques of LbL films, the methodology offers a very flexible route to a virtually limitless collection of functional smart nanopapers.