SERS detection of biomolecules using lithographed nanoparticles towards a reproducible SERS biosensor

In this paper we highlight the accurate spectral detection of bovine serum albumin and ribonuclease-A using a surface-enhanced Raman scattering (SERS) substrate based on gold nanocylinders obtained by electron-beam lithography (EBL). The nanocylinders have diameters from 100 to 180 nm with a gap of 200 nm. We demonstrate that optimizing the size and the shape of the lithographed gold nanocylinders, we can obtain SERS spectra of proteins at low concentration. This SERS study enabled us to estimate high enhancement factors (10(5) for BSA and 10(7) for RNase-A) of important bands in the protein Raman spectrum measured for 1 mM concentration. We demonstrate that, to reach the highest enhancement, it is necessary to optimize the SERS signal and that the main parameter of optimization is the LSPR position. The LSPR have to be suitably located between the laser excitation wavelength, which is 632.8 nm, and the position of the considered Raman band. Our study underlines the efficiency of gold nanocylinder arrays in the spectral detection of proteins.     

Self-assembled colloidal arrays as three-dimensional nanofluidic sieves for separation of biomolecules on microchips

We report on a biomolecular sieving system based on the use of ordered colloidal arrays to define the sieve structure within a microfluidic device. A facile microfluidic colloidal self-assembly strategy has been developed to create ordered, robust, three-dimensional nanofluidic sieves within microfluidic devices, with which fast separation of DNA and proteins of a wide size range was achieved. Compared to conventional colloidal deposition procedures, such as vertical deposition, this approach features much faster assembling speed, the absence of drying-caused cracks that may jeopardize the separation performance, and better flexibility to couple with current microfabrication techniques. The flexibility of pore size enabled by this methodology provides separation of biomolecules with a wide size distribution, ranging from proteins (20-200 kDa) to dsDNA (0.05-50 kbp). Under moderate electric fields, complete separation can be finished in minutes, with separation efficiency comparable to gel/polymer-filled or micro-/nanofabricated microsystems. To our knowledge, this is the first demonstration of size separation of biomolecules within self-assembled ordered colloidal lattices embedded within a microfluidic system.     

Ultrasensitive detection and characterization of biomolecules using superchiral fields

The spectroscopic analysis of large biomolecules is important in applications such as biomedical diagnostics and pathogen detection, and spectroscopic techniques can detect such molecules at the nanogram level or lower. However, spectroscopic techniques have not been able to probe the structure of large biomolecules with similar levels of sensitivity. Here, we show that superchiral electromagnetic fields, generated by the optical excitation of plasmonic planar chiral metamaterials, are highly sensitive probes of chiral supramolecular structure. The differences in the effective refractive indices of chiral samples exposed to left- and right-handed superchiral fields are found to be up to 10(6) times greater than those observed in optical polarimetry measurements, thus allowing picogram quantities of adsorbed molecules to be characterized. The largest differences are observed for biomolecules that have chiral planar sheets, such as proteins with high β-sheet content, which suggests that this approach could form the basis for assaying technologies capable of detecting amyloid diseases and certain types of viruses.     

Free-space optical module configuration using a guide-frame assembly method

A new assembly method is described for easy construction of optical modules consisting of guide frames, spacer frames, and a housing frame. This method is used to assemble a two-dimensional optical-fiber collimator and a digital discrete correlator, which are fundamental parts of free-space optical computing systems. We show that a multistage optical system can be constructed simply by stacking of several optical functional blocks. Moreover, these compact modules do not need a conventional optical bench, they are compact, and assembly time is reduced. We demonstrated by experiment that the accuracy of optical modules assembled with this method is within the specifications of the optical system.     

In situ magnetoresistance measurements of a nanoconstricted nickel-iron film with in-plane configuration

A test element (TE) with an Ni-Fe point contact (PC) in planar configuration was fabricated using an etching process with a horizontal incidence ion beam. Successive in situ magnetoresistance (MR) measurements were carried out in the etching apparatus without breaking the vacuum to prevent the oxidation of the PC. The TE showed the MR ratio around 12%, which was much larger than an anisotropic MR ratio of the film. It showed low (high) resistance with a magnetic field direction of parallel (antiparallel) magnetic geometry of the pinned and free area.     

Production of muons for fusion catalysis using a migma configuration

Muon-catalyzed fusion requires a very efficient means of producing muons. We describe a muon-producing magnetic-mirror scheme with triton migma that may be more energy efficient than any heretofore proposed. If one could catalyze 200 fusions per muon and employ a uranium blanket that would multiply the neutron energy by a factor of 10, one might produce electricity with an overall plant efficiency (ratio of electric energy produced to nuclear energy released) approaching 30%.The self-colliding arrangement of triton orbits will result in many π⁻'s being produced near the axis of the magnetic mirror. The pions quickly decay into muons, which are transported into a small (few cm diameter) reactor chamber producing approximately 1 MW/m² neutron flux on the chamber walls.     

Building three-dimensional images using a time-reversal chaotic cavity

The design of two-dimensional (2-D) arrays for three-dimensional (3-D) ultrasonic imaging is a major challenge in medical and nondestructive applications. Thousands of transducers are typically needed for focusing and steering in a 3-D volume. In this article, we propose a different concept allowing us to obtain electronic 3-D focusing with a small number of transducers. The basic idea is to couple a small number of transducers to a chaotic reverberating cavity with one face in contact with the body of the patient. The reverberations of the ultrasonic waves inside the cavity create at each reflection virtual transducers. The cavity acts as an ultrasonic kaleidoscope multiplying the small number of transducers and creating a much larger virtual transducer array. By exploiting time-reversal processing, it is possible to use collectively all the virtual transducers to focus a pulse everywhere in a 3-D volume. The reception process is based on a nonlinear pulse-inversion technique in order to ensure a good contrast. The feasibility of this concept for the building of 3-D images was demonstrated using a prototype relying only on 31 emission transducers and a single reception transducer.     

Interactive three-dimensional ultrasound using a programmable multimedia processor

We developed an interactive three-dimensional (3D) ultrasound (US) workstation that is inexpensive and suitable for use in research and clinical environments. Our personal computer–based system produces 3D volumes by acquiring a series of 2D images from a commercial ultrasound scanner, spatially registering the images using an electromagnetic position sensor, and reconstructing the data into a regular 3D Cartesian volume. The 3D US system uses an imaging board based on the Texas Instruments TMS320C80 Multimedia Video Processor (MVP), a fully programmable mediaprocessor that includes multiple processing units on a single chip. We developed efficient volume reconstruction and visualization algorithms for the MVP that allow our 3D US system to provide the same immediate feedback as current 2D US technologies with the added advantage of presenting information in three dimensions. For example, for acquired sequences of 512 × 512 US images, volumes can be reconstructed using six degree-of-freedom position measurements at 11.4 frames/s. A modified reconstruction algorithm that performs incremental reconstruction was developed to enable real-time volume reconstruction and visualization during acquisition and operates at 12.5 frames/s. US volumes can be rendered via shear-warp factorization and maximum intensity projection (MIP) at 10 frames/s for 128 × 128 × 128 volumes and 1.45 frames/s for 255 × 255 × 255 volumes. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol 9: 442–454, 1998     

Mechanism concept retrieval using configuration space

When designing mechanisms, making use of examples in past designs and handbooks should lead to cost reduction by promoting the sharing of parts and subassemblies among the products as well as reduction of time and effort. At present, however, the process of surveying design examples is left almost entirely to human designers and little computerised aid has been developed. We propose a computerised method of retrieving mechanism concepts from a library by specifying a required behaviour using qualitative configuration space as a retrieval index. First, mechanism concepts and their kinematics characteristics are described and stored in a computerised library using qualitative configuration spaces accompanined by additional information such as motion type and motion transmission direction. To retrieve mechanism concepts which realise specific kinematic behaviour, designers specify the required behaviour as timing charts of given input and intended output motions. Motion types, motion transmission direction, and motion speed dependence of the input and output motions can also be specified. Computer programs translate the required timing charts into required locus patterns in motion parameter space, and then available mechanism concepts to realise the behaviour are retrieved based on pattern matching between the qualitative configuration spaces and the locus patterns. The method is implemented as an experimental computer program written in Prolog and applied to simple mechanism design problems as examples to confirm the effectiveness of the approach.     

Locating flaws in three-dimensional space using a transmitter-receiver system

Using a focused probe as a transmitter and a separate transducer as a receiver, equations are derived to locate a defect in three-dimensional space. Collected experimental data confirm the applicability of the analysis. The method will be useful for acoustical imaging.     

Integral three-dimensional television using a 2000-scanning-line video system

We have developed an integral three-dimensional (3-D) television that uses a 2000-scanning-line video system that can shoot and display 3-D color moving images in real time. We had previously developed an integral 3-D television that used a high-definition television system. The new system uses -6 times as many elemental images [160 (horizontal) x 118 (vertical) elemental images] arranged at -1.5 times the density to improve further the picture quality of the reconstructed image. Through comparison an image near the lens array can be reconstructed at -1.9 times the spatial frequency, and the viewing angle is -1.5 times as wide.     

Spatially resolved scattering correlation spectroscopy using a total internal reflection configuration

In the paper, we present a novel single particle method, named spatially resolved scattering correlation spectroscopy (SRSCS), based on a total internal reflection (TIR) configuration and strong resonance light scattering (RLS) of silver nanoparticles (AgNPs). The principle of SRSCS is similar to fluorescence correlation spectroscopy (FCS), and it is based on measuring the RLS fluctuations in a small volume due to Brownian motion of single nanoparticles. We first established a highly sensitive SRSCS system. In the SRSCS system, a millimeter-scale hole is employed to efficiently separate nanoparticle scattering light from the background reflected beam, and an electron multiplying charge-coupled device (EMCCD) is used as an array detector. The SRSCS system was successfully used for detection and imaging of single AgNPs in solution. Furthermore, we developed the model of SRSCS according to the FCS method and systematically investigated the effects of certain factors such as particle concentration, viscosity of the solution, hardware and software binning and accumulation time on SRSCS measurements using AgNPs as a model sample. A series of calibration experiments were conducted, and the experimental data obtained were in good agreement with the SRSCS model. This new method is multiplexing, spatially resolved, and free of photobleaching and may become a useful method for study on heterogeneous systems, such as the motion of proteins on the cell membrane.     

Synthesis of nanorods and nanowires using biomolecules under conventional- and microwave-hydrothermal conditions

In this paper, we review our work on the synthesis and characterization of one-dimensional (1D) nanorods/nanowires and assemblies of inorganic materials with the assistance of several biomolecules under conventional- or microwave-hydrothermal conditions. Two classes of biomolecules have been investigated. One is sugars and their derivatives, and the other is amino acids and their polymers, peptide, and protein. With the assistance of sugars or their derivatives, different kinds of 1D elemental tellurium (Te) and selenium (Se) nanostructures with different sizes and morphologies have been obtained. With the assistance of amino acids or their polymers, 1D semiconductor sulfides and oxide nanowires and assemblies have been successfully synthesized. By providing confined spaces or serving as functional templates for site-specific nanomaterials nucleation or binding, biomolecules appear to direct the growth and/or the assembly of the nanomaterials.     

Enhanced three-dimensional deconvolution microscopy using a measured depth-varying point-spread function

We present a technique to systematically measure the change in the blurring function of an optical microscope with distance between the source and the coverglass (the depth) and demonstrate its utility in three-dimensional (3D) deconvolution. By controlling the axial positions of the microscope stage and an optically trapped bead independently, we can record the 3D blurring function at different depths. We find that the peak intensity collected from a single bead decreases with depth and that the width of the axial, but not the lateral, profile increases with depth. We present simple convolution and deconvolution algorithms that use the full depth-varying point-spread functions and use these to demonstrate a reduction of elongation artifacts in a reconstructed image of a 2 microm sphere.     

Synthetically programmable nanoparticle superlattices using a hollow three-dimensional spacer approach

Crystalline nanoparticle arrays and superlattices with well-defined geometries can be synthesized by using appropriate electrostatic, hydrogen-bonding or biological recognition interactions. Although superlattices with many distinct geometries can be produced using these approaches, the library of achievable lattices could be increased by developing a strategy that allows some of the nanoparticles within a binary lattice to be replaced with 'spacer' entities that are constructed to mimic the behaviour of the nanoparticles they replace, even though they do not contain an inorganic core. The inclusion of these spacer entities within a known binary superlattice would effectively delete one set of nanoparticles without affecting the positions of the other set. Here, we show how hollow DNA nanostructures can be used as 'three-dimensional spacers' within nanoparticle superlattices assembled through programmable DNA interactions. We show that this strategy can be used to form superlattices with five distinct symmetries, including one that has never before been observed in any crystalline material.     

Evaluation of three-dimensional effects in short deep beams using a rigid-body-spring-model

Three-dimensional (3-D) effects in short deep beams without stirrups that failed in shear were investigated experimentally and analytically. Two deep beams with a shear span to depth ratio (a/d) of 0.5 and with different beam widths were tested. The effect of beam width on load-carrying capacity, failure mode, crack pattern and 3-D behavior was investigated, and shape effect due to beam width was clarified. In addition, the beams were analyzed by the 3-D rigid-body-spring model (RBSM). RBSM is a discrete form of modeling that presents realistic behavior from cracking to failure, and 3-D RBSM is applicable to simulate 3-D behavior as well as the confinement effect of concrete. Analytical results in terms of load–displacement curves and crack pattern are compared with the experimental results. Three-dimensional deformations, strut widths and cross-sectional stress distribution are investigated analytically and compared with the experimental results to determine 3-D behavior in detail. The 3-D effects in short deep beams are clarified.     

Detection of biomolecules on surfaces using ion-beam-induced desorption and multiphoton resonance ionization.

Multiphoton resonance ionization (MPRI) has been combined with ion-beam-induced desorption to examine a set of thermally labile biological molecules present on surfaces. Specifically, we have examined films of adenine and beta-estradiol, molecules with a rigid skeletal backbone. In both of these cases, molecular ions could be produced efficiently without cooling the neutral molecules into their ground vibrational state. We have also studied other more fragile molecules such as tryptamine, tryptophan, phenylalanine, and serotonin. The base peak in the mass spectra of these molecules is fragment ions formed by losses of the amine side chains. Even with this fragmentation, however, it is possible to achieve sensitivity limits that are many orders of magnitude greater than for secondary ion mass spectrometry, without preparing the samples in special matrices. For serotonin, detection limits of 40 fmol on the surface of a silicon target are achievable. The results also yield a linear relation between the serotonin base fragment ion intensity and the known surface concentration.     

A general method for patterning gradients of biomolecules on surfaces using microfluidic networks

This report outlines a general method for the fabrication of immobilized gradients of biomolecules on surfaces. This method utilizes a microfluidic network that generates a gradient of avidin in solution and immobilizes this protein on the surface of glass or poly(dimethylsiloxane) by physical adsorption. The immobilized gradient of avidin is then translated into gradients of biotinylated ligands (e.g., small molecules, oligomers of DNA, polysaccharides) using the specific interaction between biotin and avidin. This method can also generate immobilized gradients of certain proteins and artificial polymers by a direct transfer of gradients from solution onto the surface. The major advantage of this method is that almost any type of molecule can, in principle, be immobilized in a well-defined surface gradient of arbitrary shape with dimensions of a few micrometers to a few centimeters. It is possible to tailor the precise shapes of gradients on surfaces from gradients in solution, either kinetically or competitively. Kinetic methods rely on controlling the time that the surface is exposed to the gradient in solution: when a single protein adsorbs from solution, the amount that adsorbs depends both on its concentration in solution and on the time allowed for adsorption. Competitive methods rely on exposure of the surface to a complementary gradient of two proteins in solution (In these experiments, the sum of the concentrations of the proteins in solution is independent of positions although the concentration of each, individually, depends on the position. In this procedure, the relative amount of each protein, at saturation on the surface, depends only on its concentration.).