High sensitivity refractive index sensor based on simple diffraction from phase grating

We present a technique for refractive index sensing using a phase grating structure. A grating under normal incidence can be designed such that the 1st order diffracted light travels at a diffraction angle of 90o with respect to the 0th order. The diffracted light which is along the direction of periodicity can further get diffracted from the grating and interfere with the 0th order light. Under this condition, the π phase difference that arises between the two interfering beams results in a transmission dip. We can tune this dip wavelength for senor applications, based on the grating equation. Both simulation and experimental data are presented in the paper which shows good agreement with each other

Magnetic Nanoparticle-Based Nano-Grating Guided-Mode Resonance Biosensors

Biomolecular detection systems based on monitoring changes in the refractive indices of functionalized surfaces are promising for applications as chemical and biological sensors. Here, we describe the design and figures of merit of our refractive index-based guided-mode resonance (GR) biosensor consisting of thin film silicon nitride sub-wavelength nano-gratings. The sensitivity of our nano-grating GR sensor was experimentally determined to be 59.3 nm per refractive index unit. We describe how the wavelength for maximum intensity of diffraction (peak wavelength) of nano-gratings was affected when functionalized magnetic nanoparticles (MNPs) were attached onto GR sensor surfaces. Moreover, we demonstrate with avidin-biotin model experiments that attaching MNPs to sensor surfaces enhances the dynamic range of detection of the GR system detection. The peak wavelength value (PWV) shifted by 0.35 nm in the case of avidin with a concentration of avidin 400 nmol/L immobilized on the sensor surface. In contrast, we achieved a 1.41 nm PWV shift after adding 5% MNPs to the solution of avidin. Not only did the MNPs enhance the dynamic range of detection, but also magnetically induced interaction of avidin-biotin significantly reduced the detection time

導波モード共鳴効果およびスマートフォン技術を集積した携帯型医療診断プラットフォームの構築

電気通信大学201

導波モード共鳴効果およびスマートフォン技術を集積した携帯型医療診断プラットフォームの構築

電気通信大学201

Wide wavelength range tunable one-dimensional silicon nitride nano-grating guided mode resonance filter based on azimuthal rotation

We describe wavelength tuning in a one dimensional (1D) silicon nitride nano-grating guided mode resonance (GMR) structure under conical mounting configuration of the device. When the GMR structure is rotated about the axis perpendicular to the surface of the device (azimuthal rotation) for light incident at oblique angles, the conditions for resonance are different than for conventional GMR structures under classical mounting. These resonance conditions enable tuning of the GMR peak position over a wide range of wavelengths. We experimental demonstrate tuning over a range of 375 nm between 500 nm˜875 nm. We present a theoretical model to explain the resonance conditions observed in our experiments and predict the peak positions with show excellent agreement with experiments. Our method for tuning wavelengths is simpler and more efficient than conventional procedures that employ variations in the design parameters of structures or conical mounting of two-dimensional (2D) GMR structures and enables a single 1D GMR device to function as a high efficiency wavelength filter over a wide range of wavelengths. We expect tunable filters based on this technique to be applicable in a wide range of fields including astronomy and biomedical imaging

Regulation of Skeletal Muscle Function by Amino Acids

Amino acids are components of proteins that also exist free-form in the body; their functions can be divided into (1) nutritional, (2) sensory, and (3) biological regulatory roles. The skeletal muscle, which is the largest organ in the human body, representing ~40% of the total body weight, plays important roles in exercise, energy expenditure, and glucose/amino acid usage—processes that are modulated by various amino acids and their metabolites. In this review, we address the metabolism and function of amino acids in the skeletal muscle. The expression of PGC1α, a transcriptional coactivator, is increased in the skeletal muscle during exercise. PGC1α activates branched-chain amino acid (BCAA) metabolism and is used for energy in the tricarboxylic acid (TCA) cycle. Leucine, a BCAA, and its metabolite, β-hydroxy-β-methylbutyrate (HMB), both activate mammalian target of rapamycin complex 1 (mTORC1) and increase protein synthesis, but the mechanisms of activation appear to be different. The metabolite of valine (another BCAA), β-aminoisobutyric acid (BAIBA), is increased by exercise, is secreted by the skeletal muscle, and acts on other tissues, such as white adipose tissue, to increase energy expenditure. In addition, several amino acid-related molecules reportedly activate skeletal muscle function. Oral 5-aminolevulinic acid (ALA) supplementation can protect against mild hyperglycemia and help prevent type 2 diabetes. β-alanine levels are decreased in the skeletal muscles of aged mice. β-alanine supplementation increased the physical performance and improved the executive function induced by endurance exercise in middle-aged individuals. Further studies focusing on the effects of amino acids and their metabolites on skeletal muscle function will provide data essential for the production of food supplements for older adults, athletes, and individuals with metabolic diseases

Magnetic-Particle-Sensing Based Diagnostic Protocols and Applications

Magnetic particle-labeled biomaterial detection has attracted much attention in recent years for a number of reasons; easy manipulation by external magnetic fields, easy functionalization of the surface, and large surface-to-volume ratio, to name but a few. In this review, we report on our recent investigations into the detection of nano-sized magnetic particles. First, the detection by Hall magnetic sensor with lock-in amplifier and alternative magnetic field is summarized. Then, our approach to detect sub-200 nm diameter target magnetic particles via relatively large micoro-sized “columnar particles” by optical microscopy is described. Subsequently, we summarize magnetic particle detection based on optical techniques; one method is based on the scattering of the magnetically-assembled nano-sized magnetic bead chain in rotating magnetic fields and the other one is based on the reflection of magnetic target particles and porous silicon. Finally, we report recent works with reference to more familiar industrial products (such as smartphone-based medical diagnosis systems and magnetic removal of unspecific-binded nano-sized particles, or “magnetic washing”)

Fast and sensitive medical diagnostic protocol based on integrating circular current lines for magnetic washing and optical detection of fluorescent magnetic nanobeads

Magnetic nanoparticles (MNPs) are increasingly being used as ‘magnetic labels’ in medical diagnostics. Practical applications of MNPs necessitate reducing their non-specific interactions with sensor surfaces that result in noise in measurements. Here we describe the design and implementation of a sensing platform that incorporates circular shaped current lines that reduce non-specific binding by enabling the “magnetic washing” of loosely attached MNPs attached to the senor surface. Generating magnetic fields by passing electrical currents through the circular shaped current lines enabled the capture and collection of fluorescent MNPs that was more efficient and effective than straight current lines reported to-date. The use of fluorescent MNPs allows their optical detection rather than with widely used magnetoresistive sensors. As a result our approach is not affected by magnetic noise due to the flow of currents. Our design is expected to improve the speed, accuracy, and sensitivity of MNPs based medical diagnostics. Keywords: Biosensors, Magnetic beads, Fluorescent magnetic nanoparticles, Lab on chip, Point of care testin