Application of a Waveguide-Mode Sensor to Blood Testing for Hepatitis B Virus, Hepatitis C Virus, Human Immunodeficiency Virus and Infection.

Testing for blood-transmitted infectious agents is an important aspect of safe medical treatment. During emergencies, such as significant earthquakes, many patients need surgical treatment and/or blood transfusion. Because a waveguide mode (WM) sensor can be used as a portable, on-site blood testing device in emergency settings, we have previously developed WM sensors for detection of antibodies against hepatitis B virus and hepatitis C virus and for forward ABO and Rh(D) and reverse ABO blood typing.

Sensitive typing of reverse ABO blood groups with a waveguide-mode sensor.

Portable, on-site blood typing methods will help provide life-saving blood transfusions to patients during an emergency or natural calamity, such as significant earthquakes. We have previously developed waveguide-mode (WM) sensors for forward ABO and Rh(D) blood typing and detection of antibodies against hepatitis B virus and hepatitis C virus. In this study, we evaluated a WM-sensor for reverse ABO blood typing.

Detection of antibodies against hepatitis B virus surface antigen and hepatitis C virus core antigen in plasma with a waveguide-mode sensor.

In large-scale disasters, such as huge significant earthquakes, on-site examination for blood typing and infectious disease screening will be very helpful to save lives of victims who need surgical treatment and/or blood transfusion. However, physical damage, such as building collapse, electric power failure and traffic blockage, disrupts the capacity of the medical system. Portable diagnostic devices are useful in such cases of emergency.

Parallel-incidence-type waveguide-mode sensor with spectral-readout setup.

A waveguide-mode sensor of the spectral-readout type can be used to detect changes in the complex refractive index in the vicinity of the surface of a sensing plate by observing the change in the spectrum of light reflected on the surface. The sensor's configuration can be simplified by adopting a parallel-incidence-type optical setup. To obtain a high sensitivity, the optimization of the sensing-plate structure, incidence angle, and detection wavelength band is essential for the sensor.

Evaluation of anti-A/Udorn/307/1972 antibody specificity to influenza A/H3N2 viruses using an evanescent-field coupled waveguide-mode sensor.

Discrimination of closely related strains is a key issue, particularly for infectious diseases whose incidence fluctuates according to variations in the season and evolutionary changes. Among infectious diseases, influenza viral infections are a worldwide cause of pandemic disease and mortality. With the emergence of different influenza strains, it is vital to develop a method using antibodies that can differentiate between viral types and subtypes.

Generation of anti-influenza aptamers using the systematic evolution of ligands by exponential enrichment for sensing applications.

The systematic evolution of ligands by exponential enrichment (SELEX) is a selection process for identifying high-affinity selective molecules from a randomized combinatorial nucleic acid library against a wide range of target molecules. Using a pool of N25 RNA molecules, the SELEX process was performed against two targets from influenza viruses, namely, intact influenza B/Tokio/53/99 and hemagglutinin of infuluenza B Jilin/20/2003. The selection processes were evaluated by surface plasmon fluorescence spectroscopy (SPFS), and the result was compared to that obtained by a conventional radioisotope method.

Colorimetric detection of controlled assembly and disassembly of aptamers on unmodified gold nanoparticles.

Aptamers are nucleic acid ligands that are generated artificially by in vitro selection and behave similar to antibodies. The development of aptamer-based sensing systems or strategies has been in vogue for the past few decades, because aptamers are smaller in size, stable, cheaper and undergo easier modifications. Owing to these advantages, several facile aptamer-based colorimetric strategies have been created by controlling the assembly and disassembly of aptamers on unmodified gold nanoparticle probes.

Observations of immuno-gold conjugates on influenza viruses using waveguide-mode sensors.

Gold nanoparticles were conjugated to an antibody (immuno-AuNP) against A/Udorn/307/1972 (H3N2) influenza virus to detect viruses on a sensing plate designed for an evanescent field-coupled waveguide-mode sensor. Experiments were conducted using human influenza A/H3N2 strains, and immuno-AuNP could detect 8×10(5) PFU/ml (40 pg/µl) intact A/Udorn/307/1972 and 120 pg/µl A/Brisbane/10/2007. Furthermore, increased signal magnitude was achieved in the presence of non-ionic detergent, as the virtual detection level was increased to 8×10(4) PFU/ml A/Udorn/307/1972.

A high-performance waveguide-mode biosensor for detection of factor IX using PEG-based blocking agents to suppress non-specific binding and improve sensitivity.

An evanescent-field-coupled waveguide-mode (EFC-WM) sensor utilizes monolithic SiO2/Si/SiO2 sensing plates having a multilayered structure and is used to evaluate a blocking agent comprising poly(ethylene glycol)-based block copolymers. Factor IX (FIX) protein was detected using its aptamer, viz. FIX was immobilized on a glutaraldehyde-modified silica surface, and then treated with a biotinylated aptamer.

Surface functionalization chemistries on highly sensitive silica-based sensor chips.

The surfaces of silica-based sensor chips, designed for evanescent-field-coupled waveguide-mode sensors, were functionalized using various surface chemistries. The immobilization of molecular entities on the functionalized silica surfaces was monitored using various microscopic techniques (scanning electron, fluorescence, and atomic force microscopies). Further, gold nanoparticle-based signal enhancement analyses were performed with protein conjugation on different functionalized surfaces using a waveguide-mode sensor.

Waveguide-mode sensors as aptasensors.

Aptamers are artificial nucleic acid ligands that can be generated by in vitro selection through partition and amplification. Aptamers can be generated against a wide range of biomolecules through the formation of versatile stem-loop structures. Because aptamers are potential substitutes for antibodies and drugs, the development of an aptamer-based sensor (aptasensor) is mandatory for diagnosis.

Optimal design of a spectral readout type planar waveguide-mode sensor with a monolithic structure.

Optical planar waveguide-mode sensor is a promising candidate for highly sensitive biosensing techniques in fields such as protein adsorption, receptor-ligand interaction and surface bacteria adhesion. To make the waveguide-mode sensor system more realistic, a spectral readout type waveguide sensor is proposed to take advantage of its high speed, compactness and low cost. Based on our previously proposed monolithic waveguide-mode sensor composed of a SiO2 waveguide layer and a single crystalline Si layer [1], the mechanism for achieving high sensitivity is revealed by numerical simulations.

Shape-sensitive reflectance by nanostructured metal attached on an optical waveguide-mode sensor.

The optical reflectance of He-Ne laser light on a waveguide-mode sensor was measured as a function of light incident angle, in the case of either a metal (Au, Cr or Pt) film or nanoparticles being attached to the waveguide surface of the sensor. A dip appears in the reflectance spectrum as a function of incident angle at the angle where waveguide-mode excitation is induced. It is found that the dip moves toward a lower angle in the case that the attached metal is of a film shape, while it shifts toward a higher angle when the metal is an ensemble of nanoparticles.

Optimization of silica surface with nanosize holes for immobilization of biomolecules and analysis of their interactions.

An evanescent-field-coupled waveguide-mode sensor of the Kretschmann configuration with a silica waveguide having nanoscale holes is an ideal tool for detection of bimolecular reactions. In the present research, an optimized surface of the sensor with cylindrical nanoscale holes was modified with sodium (1-{[6-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)hexanoyl]oxy}-2,5-dioxopyrrolidine-3-sulfonate) (Sulfo-EMCS) to facilitate the attachment of biomolecules; the resulting surface could be cleaned for reuse simply by changing the pH of the buffering solution. The modification is expected to be useful for wide range of molecular detection.

Detection of colored nanomaterials using evanescent field-based waveguide sensors.

We have developed an optical system designed for detecting colored nanomaterials in aqueous solutions, using the concept of evanescent-field-coupled waveguide-mode sensors. In this study, we found that the waveguide modes induced in the sensor are intrinsically sensitive to a change in optical absorption, or a 'change in color'. The system detects less than one gold nanoparticle (diameter: 20 nm) adsorbed per square micrometer.

Evaluation of nucleic acid duplex formation on gold over layers in biosensor fabricated using Czochralski-grown single-crystal silicon substrate.

With a view to developing an economical and elegant biosensor chip, we compared the efficiencies of biosensors that use gold-coated single-crystal silicon and amorphous glass substrates. The reflectivity of light over a wide range of wavelengths was higher from gold layer coated single-crystal silicon substrates than from glass substrates. Furthermore, the efficiency of reflection from gold layers of two different thicknesses was examined.

Plasmonic activity on gold nanoparticles embedded in nanopores formed in a surface layer of silica glass by swift-heavy-ion irradiation.

Silica glass was irradiated by swift heavy ions by selecting the ion species and its energy in order to induce the largest damaged regions. These regions were then selectively etched by hydrofluoric acid vapour to form nanopores on the glass surface. Subsequently, gold nanoparticles were embedded into the nanopores by vacuum evaporation, followed by thermal treatment.

Proposal of a grating-based optical reflection switch using phase change materials.

We have proposed a novel grating-based optical reflection switch using a phase change material (PCM). The device switches on/off light or shifts the light propagation direction by switching the PCM grating between its amorphous and crystalline states. Thus, the switching status is non-volatile and the device is promising for realizing low power consumption.

Monitoring biological interactions using perforated evanescent-field-coupled waveguide-mode nanobiosensors.

Evanescent-field-coupled (EFC) waveguide-mode sensors recently been shown to be suitable for detecting various biomolecules. In the present studies, we demonstrated that both nucleic acids hybridization and nucleic acids-protein interactions can be analyzed using perforated evanescent-field-coupled waveguide-mode nanobio-sensors.

The fabrication of aligned pairs of gold nanorods in SiO2 films by ion irradiation.

Pairs of gold nanodisks 40 or 70 nm in diameter were fabricated in silica by electron-beam lithography. On irradiation by 110 MeV Br(10+) ions, the nanodisks elongated to form nanorods; elongation occurred in the direction of propagation of the ions. The aspect ratios of the Au nanorods increased with increasing ion-flux density or fluence and with decreasing diameter of the nanodisks.

A sensitive multilayered structure suitable for biosensing on the BioDVD platform.

Several technologies are currently available for the analysis of biomolecular interactions with high sensitivity and efficiency. However, these instruments are invariably expensive and, thus, are not suitable for bedside analyses. To circumvent this issue, we have previously reported a BioDVD platform that allowed us to use a DVD mechanism to monitor various biomolecular interactions [Gopinath et al.

Monitoring surface-assisted biomolecular assembly by means of evanescent-field-coupled waveguide-mode nanobiosensors.

Biological self-assembly is a natural process that involves various biomolecules, and finding the missing partner in these interactions is crucial for a specific biological function. Previously, we showed that evanescent-field-coupled waveguide-mode sensor in conjunction with a SiO(2) waveguide, the surfaces which contain cylindrical nanometric holes produced by atomic bombardment, allowed us to detect efficiently the biomolecular interactions. In the present studies, we showed that the assembly of biomolecules can be monitored using the evanescent-field-coupled waveguide-mode biosensor and thus provide a methodology in monitoring assembly process in macromolecular machines while they are assembling.

Monitoring biomolecular interactions on a digital versatile disk: a BioDVD platform technology.

A spinning-disk biosensor utilizing optical interference of reflected light from a multilayered structure, consisting of dielectric, metal, and optical phase-change thin films, is shown to have the potential to monitor various interactions on its surface. We refer to this platform as a BioDVD, since it utilizes the optical system of a digital versatile disk (DVD) to measure changes in reflected light intensity. Here, we demonstrated that nucleic acid hybridization and RNA-protein interactions can be analyzed efficiently, in a label-free environment, by measuring the reflected light intensity using a DVD-like mechanism.

Influence of nanometric holes on the sensitivity of a waveguide-mode sensor: label-free nanosensor for the analysis of RNA aptamer-ligand interactions.

Evanescent-field-coupled (EFC) waveguide-mode sensors can be used to detect nucleic acids or proteins from the changes in the local index of refraction upon adsorption of the target molecule on a waveguide surface. We recently described an EFC waveguide-mode sensor in which nanometric holes on a waveguide film resulted in an improved sensitivity in the analysis of the interactions of biomolecules. In the present study, we have shown that sensitivity depends upon the diameter of the holes, where increase in diameter of holes increases spectral shift resulting in an improved sensitivity.

Silica-based monolithic sensing plates for waveguide-mode sensors.

We developed a monolithic sensing plate for a waveguide-mode sensor. The plate consists of a SiO(2) glass substrate and a thin silicon layer the surface of which is thermally oxidized to form a SiO(2) glass waveguide. We confirmed that the sensing plate is suitable for high-sensitivity detection of molecular adsorption at the waveguide surface.