Guidance of neural regeneration on the biomimetic nanostructured matrix.

Biomimetic materials are used for creating microsystems to control cell growth spatially and elicit specific cellular responses by combining complex biomolecules with nanostructured surfaces. Intercellular cell-to-cell and cell-to-extracellular matrix (ECM) interactions in biomimetic materials have demonstrated potential in the development of drug discovery platforms and regeneration medicine. In this study, we developed a biomimetic nanostructured matrix by using various ECM molecular layers to create a biomimetic and biocompatible environment for realizing neuronal guidance in neural regeneration medicine. Silicon-based substrates possessing nanostructures were modified using different ECM proteins and peptides to develop a biomimetic and biocompatible environment for studying neural behaviors in adhesion, proliferation, and differentiation. The substrates were flat glass, flat silicon wafers (FWs), and nanorod-structured wafers prepared using wet etching. The three substrates were then functionalized using laminin-1 peptide, PA22-2-contained active isoleucine-lysine-valine-alanine-valine (IKVAV) peptide, and poly-d-lysine (PDL), separately. When PC12 cells were cultured and differentiated on the modified substrates, the cells were able to elongate the neurites on the glass and FW, which was coated with three types of peptide. More differentiated neurons were observed on the nanorod-structured wafers coated with laminin than on those coated with IKVAV or PDL. For achieving directional guidance of neurite outgrowth, substrates exhibiting a grating pattern of nanorods were partially collapsed by the pulling force of water, leaving few nanorods, which support the net form of laminin on the surface. Furthermore, we fabricated the topological nanostructure-patterned wafer coated with laminin and successfully manipulated the extension and direction of neurites by using more than 80 µm of a single soma. This approach demonstrates potential as a facile and efficient method for guiding the direction of single axons and for enhancing neurite outgrowth in studies on nerve regenerative medicine.

A solution-based nano-plasmonic sensing technique by using gold nanorods.

We have successfully demonstrated a novel sensing technique for monitoring the variation of solution concentrations and measuring the effective dielectric constant in a medium by means of an ultra-small and label-free nanosensor, the mechanism of which is based on the localized surface plasmon resonance (LSPR) of gold nanorods. The nanorods are fabricated in a narrow size distribution, which is characterized by transmission electron microscopy and optical absorption spectroscopy. In addition, we employ a simple analytical calculation to examine the LSPR band of the absorption spectrum, which provides excellent consistency with aspect ratio. The plasmonic sensing is performed by detecting the diffusion process and saturation concentration of hexadecyltrimethylammonium bromide in water, and tracing the effective dielectric constants of the medium simultaneously. This promising sensing and analytical technique can be easily used for investigating the nano-scale variations of mixing or reaction process in a micro/nanofluidic channel or the biological interaction in the cytoplasm of the cell.

Functionalization, re-functionalization and rejuvenation of ssDNA nanotemplates.

Single-stranded DNA (ssDNA) with repetitive sequence was demonstrated to be a versatile nanotemplate for introducing biological activity in a self-assembled manner. Re-functionalization and rejuvenation of the ssDNA nanotemplate were achieved under mild biological conditions without using high temperature and strong alkaline treatment to denature DNA.

Investigation of multiphase liquid roughness using an atomic force microscope.

The roughness of a multiphase interface and the associated topography between silicone oil and an alcohol-based fluid were measured with an atomic force microscope (AFM) and compared with the results of calculations based upon a capillary-wave model. According to this theory, the interfacial roughness of a liquid-liquid interface depends on the density, interfacial tension, and temperature of the liquids. Test samples prepared with both silicone oil and an alcohol-based fluid at various volumetric ratios and controlled temperatures were carefully measured. The experimental results indicate that the interfacial roughness measured with an AFM was consistent with the capillary-wave model. The measured interfacial roughness is influenced mainly by the interfacial tension between the liquids and the temperature-driven Brownian motion of the molecules. Three-dimensional topographical pictures of the interfaces were constructed and archived digitally for subsequent investigation. By employing the outlined method, we examined the microscopic details of interfacial properties, with prospective applications in biochemical and biophysical research.

Fabrication and optical studies of monolayer assemblies of Au nanoparticles.

Two-dimensional nanoparticle self-assemblies provide a means of tuning the optical properties by manipulation of the fabrication parameters, thereby controlling the light-matter interaction. We report fabrication of self-assembled monolayers of colloidal gold nanoparticles on organosilane-coated substrates and a study of the linear and nonlinear optical properties. With increase in particle coverage of the gold monolayer self assemblies, an additional band in the absorption spectrum due to the collective particle surface plasmon resonance could be seen. The intensity and lambda(max) of this feature depends on the interparticle spacing and particle aggregation. Z-scan measurements show a saturable absorption behavior and a negative nonlinear refractive index of the monolayer films. A strong correlation between particle density and the linear and nonlinear optical properties is established.

Localization of optical fields using a bow-tie nanoantenna.

Localization of optical fields in a bow-tie nanoantenna is studied using a high-frequency structure simulator (HFSS). Simulation results show a strong localization effect in the gap of the antenna. The enhanced intensity in the gap is due to the surface plasmon resonance and the concentration of energy flow.