Bacterial adhesion onto nanopatterned polymer surfaces

Two-dimensional nanopore arrays, consisting of hydrophilic SiO₂-like holes within hydrophobic poly(hydroxymethylsiloxane) (PHMS) surfaces, were fabricated by using a colloidal template-assisted method. The pores typically were deep 2–3 nm and wide ∼100 nm, as measured by tapping mode AFM. The adhesion behaviour of Pseudomonas aeruginosa, i.e. a micrometer width cell, was investigated by Fluorescence Microscopy both onto the nanopatterned PHMS surfaces and the homogeneous corresponding substrates of unmodified PHMS as well as the SiO₂-like surfaces obtained by plasma modification of PHMS films. The nanostructured films were able to induce a general increase of adhered cells with respect to the unmodified hydrophobic surfaces and a spot grown of biofilm-like aggregates. The observed effects are discussed in terms of the surface free energy of the patterned films as well as of the homogeneity and total integrated area of the 2D nanopore array.     

Simulation of grafted polymers on nanopatterned surfaces

Structural properties of polymer brushes on nanopatterned surfaces in good solvent have been determined by computer simulations. Scaling relations for the brush height and brush width are proposed. The properties of the central part of the patterned brush remain constant as long as the pattern is wider than a few times the brush height. The results agree qualitatively with recent AFM experiments, but some quantitative differences call for a reassessment of experimental procedures.     

Strongly anisotropic wetting on one-dimensional nanopatterned surfaces

This communication reports strongly anisotropic wetting behavior on one-dimensional nanopatterned surfaces. Contact angles, degree of anisotropy, and droplet distortion are measured on micro- and nanopatterned surfaces fabricated with interference lithography. Both the degree of anisotropy and the droplet distortion are extremely high as compared with previous reports because of the well-defined nanostructural morphology. The surface is manipulated to tune with the wetting from hydrophobic to hydrophilic while retaining the structural wetting anisotropy with a simple silica nanoparticle overcoat. The wetting mechanisms are discussed. Potential applications in microfluidic devices and evaporation-induced pattern formation are demonstrated.     

Use of nanopatterned surfaces to enhance immunoreaction efficiency

In this work, we compare the immunoreaction efficiency between uniformly functionalized surface and chemically nanopatterned surfaces when applied as platforms for antigen/antibody interactions with and without the use of protein A as orienting protein. On the nanopatterned platform, the immunoreaction efficiency is higher than all the other cases with no protein A pretreatment of the surface, providing evidence of the capability of the adhesive/antiadhesive nanopatterned surface to immobilize the molecules in a reactive state, increasing their possibility to form complexes.     

Conjugation of active iron superoxide dismutase to nanopatterned surfaces

Superoxide dismutase enzymes (SODs) are an essential part of the first line of cellular defense system against free radicals species. They catalyze the dismutation of superoxide radicals into oxygen and hydrogen peroxide. Although several studies have examined the attachment of superoxide dismutases to nanoparticles and nanostructures, never has been used a member of the Fe/MnSOD family. In this study, the behavior of plant origin FeSOD enzyme on three different nanopatterned surfaces was investigated as a function of covalent and electrostatic binding. Fluorescence microscopy was used to demonstrate that the protein is attached only to the gold layer. We also examined the activity of SOD by a colorimetric assay, and we have shown that the enzyme remains active after attachment to the three different surfaces under both kind of binding (electrostatic and covalent). This methodology could be useful for those who want to functionalize nanostructures with a SOD enzyme and test the activity. This process could be of great interest for the development of peroxynitrite and superoxide biosensors.     

Chemically nanopatterned surfaces using polyelectrolytes and ultraviolet-cured hard molds

Polymer transfer printing of poly(acrylic acid) onto a polyelectrolyte multilayer platform resulted in chemically nanopatterned surfaces with well-defined structures and both positive and negative surface functionalities. A commercially available urethane-related photopolymer cured by ultraviolet light was used to make stamps for contact printing with a range of submicrometer down to 80 nm features because of its outstanding mechanical stability and inherent softening transition above 48 degrees C.     

Separation of DNA with different configurations on flat and nanopatterned surfaces

We demonstrate that electrophoresis on a flat Si substrate is an effective method in separation of DNA with different configurations, e.g., linear, supercoiled, and relaxed or DNA of different length, e.g., supercoiled DNA ladder. The surface separation arises from the different number of contacts due to the conformational differences between adsorbed DNA chains. Imposing a Au nanopattern on the Si surface further improves the separation effect. The simulation of electric field on this patterned surface by the finite element method shows that Au nanodots act as local pinning points for DNA segments due to dielectrophoretic force. The results of molecular dynamics simulation showed that the conformational differences between adsorbed polymer chains were amplified on the patterned surface and enhanced separations were achieved, which are consistent with the experimental results.     

Ceramic nanopatterned surfaces to explore the effects of nanotopography on cell attachment

Surfaces with ordered, nanopatterned roughness have demonstrated considerable promise in directing cell morphology, migration, proliferation, and gene expression. However, further investigation of these phenomena has been limited by the lack of simple, inexpensive methods of nanofabrication. Here, we report a facile, low-cost nanofabrication approach based on self-assembly of a thin-film of gadolinium-doped ceria on yttria-stabilized zirconia substrates (GDC/YSZ). This approach yields three distinct, randomly-oriented nanofeatures of variable dimensions, similar to those produced via polymer demixing, which can be reproducibly fabricated over tens to hundreds of microns. As a proof-of-concept, we examined the response of SK-N-SH neuroblastoma cells to features produced by this system, and observed significant changes in cell spreading, circularity, and cytoskeletal protein distribution. Additionally, we show that these features can be imprinted into commonly used rigid hydrogel biomaterials, demonstrating the potential broad applicability of this approach. Thus, GDC/YSZ substrates offer an efficient, economical alternative to lithographic methods for investigating cell response to randomly-oriented nanotopographical features.     

Controlling the location and spatial extent of nanobubbles using hydrophobically nanopatterned surfaces

The presence of nanobubbles-as imaged with tapping-mode atomic force microscopy-is controlled using nanopatterned surfaces possessing repeating patterns of polystyrene (hydrophobic domains) and poly(methyl methacrylate) (hydrophilic domains). For nanobubbles to be present, we find that, in addition to controlling the degree of surface hydrophobicity, it is important for the spatial dimensions of the hydrophobic domains on the nanopatterned surface to be commensurate with the equilibrium topology of the nanobubbles.     

Highly parallel fabrication of nanopatterned surfaces with nanoscale orthogonal biofunctionalization imprint lithography

Large areas of nanopatterns of specific chemical functionality are needed for biological experiments and biotechnological applications. We present nanoscale orthogonal biofunctionalization imprint lithography (NOBIL), a parallel top-down imprinting and lift-off technique based on step-and-flash imprint lithography (SFIL) that is able to create centimetre-scale areas of nanopatterns of two biochemical functionalities. A photoresist precursor is polymerized with a template in place, and the thin resist layer is etched to create an undercut for lift-off. Gold nano-areas on a silicon dioxide background are then independently functionalized using self-assembly that translates the nanopattern into a cell-adhesive/cell-rejective functionality pattern. We demonstrate the technique by creating fibronectin areas down to a pattern size of 60?nm against a polyethylene glycol (PEG) background, and show initial results of cells stably seeded over an array of 1?mm(2) areas of controlled size and pitch.     

Cellular unbinding forces of initial adhesion processes on nanopatterned surfaces probed with magnetic tweezers

To study the dependence of unbinding forces on the distance of molecularly defined and integrin specific c(-RGDfK-) ligand patches in initial cellular adhesion processes, we developed a magnetic tweezers setup for applying vertical forces of up to 200 pN to rat embryonic fibroblasts. The ligand patch distance is controlled with a hexagonally close packed pattern of biofunctionalized gold nanoparticles prepared by block-copolymer micelle nanolithography. Each gold nanoparticle potentially activates up to one alpha(v)beta(3)-integrin. The distances between the gold nanoparticles determine the separation of individual integrins and thus the assembly of integrin clusters. The results show an increase in cellular unbinding forces from approximately 6 to more than 200 pN for a decreasing ligand distance of 145 to 58 nm after 5 min of cell adhesion. Furthermore, we observe a strong dependence on adhesion time during the first 10 min of cell surface contact suggesting an active, cooperative cell response that is controlled by the spacing between individually activated integrins.     

Large-scale synthesis of BN nanotubes using carbon nanotubes as template

Boron nitride nanotubes (BN-NTs) were synthesized in large scale by the reaction of NaBH₄ and NH₄Cl in the temperature range of 500-600 °C for 10-18 h, where carbon nanotubes (CNTs) were mixed together with the reactants to serve as template. Pure BN-NTs were obtained by oxidizing the product at about 800 °C in air atmosphere. The structure and morphology of the product with a surface area of 106.635 m²/g were characterized by X-ray diffraction, transmission electron microscopy, Fourier transformation infrared spectroscopy, and thermogravimetric analysis. Large scale preparation of BN-NTs could be realized by this simple and effective route.     

无阻挡层多孔阳极氧化铝膜板的制备

提出一种在中性的KCl溶液中用多孔阳极氧化铝作阴极,通过电解在阴极产生OH-腐蚀阻挡层,制备无阻挡层氧化铝模板的新方法.用扫描电镜对模板进行了表征.结果表明,在草酸溶液中,制得的氧化铝模板孔径为70～80nm,孔间距为130nm,孔密度约8×109/cm2,这种方法去阻挡层不扩大模板孔径,不影响纳米孔的纵横比.无阻挡层的氧化铝模板适合于直流电沉积和无电沉积金属纳米材料.     

Characterization of nickel nanocones routed by electrodeposition without any template

This work reports the synthesis of Ni nanocones by a one-step electrodeposition method without any template. With the addition of ethylenediamine dihydrochloride (EDA·2HCl) in the nickel plating solution, the novel Ni conical structure can be easily deposited onto different metal surfaces. The as-prepared nickel nanocones grow preferentially along [Formula: see text] directions with very sharp tips. The conical structures are single crystalline without any disruption of the lattice planes. In addition, the Ni?nanocone structure is demonstrated to show magnetocrystalline anisotropy and enhance the magnetic properties when compared with other Ni?nanostructures.     

Synthesis of novel urchin-like architecture Au by self-assembly coupled without template

The formation of novel urchin-like architecture Au by hydrothermal treated method in tungstosilicate acid (H₄SiW₁₂O₄₀, TSA) solution is described. The particles are characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM), respectively. The results show that it is possible to synthesize and assemble other noble metal particles with unique superstructure with possible applications in catalysis and other fields.     

In-situ fabrication of AAO template without oxide barrier layer and its applications

Porous anodic aluminum oxide (AAO) film is the most widely used template in combination with electrodeposition (ED) method to fabricate one-dimensional nanostructures such as nanowires, nanotubes and nanorods. However, the existing oxide barrier layer after the anodization blocks the application of AAO template in synthesis of nanostructures via direct electrodeposition. In this paper, AAO template without oxide barrier layer was successfully fabricated by stepwise voltage decrement; influence of two types of stepwise voltage decrement on the removal of oxide barrier layer was introduced. Field Emission Scanning Electron Microscopy (FESEM) images indicated that stepwise voltage decrement could make the oxide layer thin effectively. Meanwhile, highly ordered gold nanowire arrays were fabricated by using direct electrodeposition method based on AAO template with the second anodization process with stepwise voltage decrement of 1 V/min, FESEM image showed that as-prepared gold nanowires are uniform in diameter and the diameter is in accordance with the diameter of AAO template pores. XRD pattern revealed that gold nanowires were indexed as face-centered cubic phase.     

Large-scale patterning of gold nanopillars in a porous anodic alumina template by replicating gold structures on a titanium barrier

Gold nanopillars are grown in patterns inside a porous anodic alumina template. On selected positions, defined by a gold "seed" pattern, gold is electroplated into the pores, while a barrier layer underneath the porous template blocks the deposition on the rest of the surface. Large-scale arrays of free-standing nanopillar islands are obtained after selective etching of the alumina template.     

Designing an optical disk lens without analytical definition of aspheric surfaces

We have developed a new method to design aspheric lenses. The conventional technique is usually based on analytic definition of optical surfaces; in the new method discretely defined aspheres are used, and the final design is attained point by point with an iterative algorithm. Simulation results are compared with results obtained with conventional optical design software to prove that this new method is more effective and reliable for designing aspheric lenses, especially when the aspheric order is high.     

Corrugated surfaces formed on GaAs(331)A substrates: the template for laterally ordered InGaAs nanowires

Morphology evolution of high-index GaAs(331)A surfaces during molecular beam epitaxy?(MBE) growth has been investigated in order to achieve regularly distributed step-array templates and fabricate spatially ordered low-dimensional nano-structures. Atomic force microscope?(AFM) measurements have shown that the step height and terrace width of GaAs layers increase monotonically with increasing substrate temperature. By using the step arrays formed on GaAs(331)A surfaces as the templates, we have fabricated highly ordered InGaAs nanowires. The improved homogeneity and the increased density of the InGaAs nanowires are attributed to the modulated strain field caused by vertical multi-stacking, as well as the effect of corrugated surface of the template. Photoluminescence?(PL) tests confirmed remarkable polarization anisotropy.