Ratthasart Amarit

ABO blood-typing using an antibody array technique based on surface plasmon resonance imaging.

In this study, readily available antibodies that are used in standard agglutination tests were evaluated for their use in ABO blood typing by a surface plasmon resonance imaging (SPR imaging) technique. Five groups of antibodies, including mixed clones of anti-A, anti-B, and anti-AB, and single clones of anti-A and anti-B, were used to construct the five-line detection arrays using a multichannel flow cell in the SPR imager. The red blood cell (RBC) samples were applied to a multichannel flow cell that was orthogonal to the detection line arrays for blood group typing. We found that the blood samples were correctly grouped in less than 12 min by the SPR imaging technique, and the results were consistent with those of the standard agglutination technique for all 60 samples. We found that mixed clones of antibodies provided 33%–68% greater change in the SPR signal than the single-clone antibodies. Applying the SPR imaging technique using readily available antibodies may reduce the costs of the antibodies, shorten the measurement time, and increase the throughput.

SPR-DNA array for detection of methicillin-resistant Staphylococcus aureus (MRSA) in combination with loop-mediated isothermal amplification

In this study, we evaluated surface plasmon resonance imaging (SPR imaging) as a DNA biosensor for the detection of methicillin-resistant Staphylococcus aureus (MRSA) which is one of the most common causes of nosocomial infections. The DNA sample were collected from clinical specimens, including sputum and blood hemoculture were undergone LAMP amplification for 0.18 kbp and 0.23 kbp DNA fragments of femB and mecA genes, respectively. The self-assembled monolayer surface (SAMs) was used for immobilized streptavidin-biotinylated probes on the sensor surface for the detection of LAMP amplicons from MRSA. Both LAMP amplicons were simultaneously hybridized with ssDNA probes immobilized onto a bio-functionalized surface to detect specific targets in the multiplex DNA array platform. In addition, the sensor surface could be regenerated allowing at least five cycles of use with a shortened assay time. The detection limit of LAMP-SPR sensing was 10 copies/µl and LAMP-SPR sensing system showed a good selectivity toward the MRSA.

Light scattering-based high contrast optical touch sensor architectures in transmissive and reflective configurations

Transmissive and reflective optical touch switch architectures based on the use of light scattering are proposed. Key features include high ON/OFF switching ratio, tunable sensitivity, ease of implementation, and no leakage optical beam incident on the user. Experimental proof of concept using a visible laser diode and a plastic Dove prism arranged in the transmissive configuration shows a high 24.4 dB contrast ratio which is a hundred times higher than obtained in the previous total internal reflection-based optical touch switch. In addition, switching response in milliseconds is also investigated for both lifting and sliding the fingertip out of the touching surface of the optical touch switch. Our light scattering-based optical touch switch also supports multiple keystroke operation.

Rh blood phenotyping (D, E, e, C, c) microarrays using multichannel surface plasmon resonance imaging

The application of Surface Plasmon Resonance Imaging (SPRi) for the detection of transmembrane antigen of the Rhesus (Rh) blood group system is demonstrated. Clinically significant Rh blood group system antigens, including D, C, E, c, and e, can be simultaneously identified via solid phase immobilization assay, which offers significant time savings and assay simplification. Red blood cells (RBCs) flowed through the micro-channel, where a suitable condition for Rh blood group detection was an RBC dilution of 1:10 with a stop-flow condition. Stop flow showed an improvement in specific binding compared to continuous flow. Rh antigens required a longer incubation time to react with the immobilized antibody than A and B antigens due to the difference in antigen type and their location on the RBC. The interaction between the immobilized antibodies and their specific antigenic counterpart on the RBC showed a significant difference in RBC removal behavior using shear flow, measured from the decay of the SPR signal. The strength of the interaction between the immobilized antibody and RBC antigen was determined from the minimum wall shear stress required to start the decay process in the SPR signal. For a given range of immobilized antibody surface densities, the Rh antigen possesses a stronger interaction than A, B, and AB antigens. Identification of 82 samples of ABO and Rh blood groups using SPRi showed good agreement with the standard micro-column agglutination technique. A wider coverage of antigenic recognition for RBC when using the solid phase immobilization assay was demonstrated for the RBC with the antigenic site located on the transmembrane protein of the clinically significant Rh antigen. Given the level of accuracy and precision, the technique showed potential for the detection of the Rh minor blood group system.

Application of surface plasmon resonance biosensor for the detection of Candida albicans

In this study, surface plasmon resonance imaging (SPR imaging) was developed for the detection of Candida albicans which is a causal agent of oral infection. The detection was based on the sandwich assay. The capture antibody was covalently immobilized on the mixed self assemble monolayers (SAMs). The ratio of mixed SAMs between 11-mercaptoundecanoic acid and 3-mercaptopropanol was varied to find the optimal ratio for use as a sensor surface. The results showed that the suitable surface for C. albicans detection was SAM of carboxylic (mixed SAMs ), even though mixed SAMs had a high detection signal in comparison to mixed SAMs , but the non-specific signal was higher. The detection limit was 107 cells/ml for direct detection, and was increased to 106 cells/ml with sandwich antibody. The use of polyclonal C. albicans antibody as capture and sandwich antibody showed good selectivity against the relevant oral bacteria including Escherichia coli, Streptococcus mutan, Staphylococcus aureus, β-streptococci, and Lactobacillus casei. SPR platform in this study could detect C. albicans from the mixed microbial suspension without requirement of skillful technician. This SPR imaging biosensor could be applied for Candida identification after cultivation.

Microfluidic PMMA-based microarray sensor chip with imaging analysis for ABO and RhD blood group typing

Solid phase microarrays have been described for use in blood typing; red blood cells (RBCs) captured on immobilized antibodies were detected using surface plasmon resonance or fluorescence. We present antibody microarray on Poly (methylmethacrylate) (PMMA) surface coupled with microfluidic system for ABO and RhD blood typing. After immobilized by antigen–antibody interaction, the RBCs were detected by image recognition.

Development and Beam-Shape Analysis of an Integrated Fiber-Optic Confocal Probe for High-Precision Central Thickness Measurement of Small-Radius Lenses

This work describes a new design of a fiber-optic confocal probe suitable for measuring the central thicknesses of small-radius optical lenses or similar objects. The proposed confocal probe utilizes an integrated camera that functions as a shape-encoded position-sensing device. The confocal signal for thickness measurement and beam-shape data for off-axis measurement can be simultaneously acquired using the proposed probe. Placing the probe’s focal point off-center relative to a sample’s vertex produces a non-circular image at the camera’s image plane that closely resembles an ellipse for small displacements. We were able to precisely position the confocal probe’s focal point relative to the vertex point of a ball lens with a radius of 2.5 mm, with a lateral resolution of 1.2 µm. The reflected beam shape based on partial blocking by an aperture was analyzed and verified experimentally. The proposed confocal probe offers a low-cost, high-precision technique, an alternative to a high-cost three-dimensional surface profiler, for tight quality control of small optical lenses during the manufacturing process.

Cost-effective neutral density filters from polydimethylsiloxane

A neutral density filter (ND) is one of the basic and important optical components used in optical and photographic systems for controlling intensity of light at all wavelengths. It is typically fabricated by coating appropriate thin films on glass or plastic substrates through an expensive time-consuming and power-hungry thin-film coating system. In this work, we show for the first time how very low-cost NDs can be implemented on a well-known Polydimethylsiloxane (PDMS) material widely used in microfluidic applications. PDMS-based NDs with 10-80% transmission and a broad wavelength operation in a visible spectrum are highlighted.

Fiber-optic confocal probe with an integrated real-time apex finder for high-precision center thickness measurement of ball lenses

This paper describes the development of a fiber-optic confocal probe suitable to measuring the central thickness of highcurvature small-diameter optical ball lenses. The confocal probe utilizes an integrated camera that functions as a realtime apex-sensing device. An additional camera is used to monitor the shape of the reflected light beam. Placing the instrument sensing spot off-center from the apex will produce a non-circular image at the camera plane that closely resembles an ellipse for small displacement. By analyzing the shape of the reflected light spot, we are able to precisely determine the focus point of the confocal probe relative to the apex point to better than 2-μm precision for ball lenses with diameters in the range of 3 – 10 mm. The proposed confocal probe offers a low-cost alternative technique for quality control of ball lenses during the manufacturing process.

Mobile-platform for automatic fever screening system based on infrared forehead temperature

In this paper, automatic fever screening system is proposed and experimentally implemented using an IR camera and a mobile phone. Our system locates position of patients automatically using face detection algorithm on RGB image and obtains temperature from IR image at detected location. Advantages are fast, portable, non-contacting and simultaneously temperature measurement. Furthermore, face detection algorithm allows the system to track patients face position. Hence, robust and non-contacting temperature measurement can be properly done even patients are not stand still. Our system has been field-tested to measure temperature and screen ill patients at a children medical clinic. In this experiment, the system is calibrated to measure temperature of patients at 1 meter away and gives an alarm sound when the measured temperature is above the desired setting threshold. According to experimental results, the correlation coefficient between temperature obtained from our system and commercial infrared forehead skin thermometer [2] is more than 0.80. In addition, our system achieves a 100% sensitivity and 70% specificity. Although our approach loses specificity, all fever patients are identified correctly. Thus, they are significantly correlated. Therefore, this system can reliably estimate body temperature of patients and can be used for effectively pre-screening fever patients.