RESUMEN
To realize highly sensitive immunoassays, high optical density probes conjugated with antibodies for target antigens have been demanded in order to increase the visibility of antigen-antibody complex formation. We herein demonstrate the development of an immunoassay system using magnetic and fluorescent Janus particles as probes in conjunction with an antibody-immobilized microfluidic device. The concentration of the detection limit at which there was a significant difference between SARS-CoV-2 and human coronavirus 229E antigens was 3.1 ng/mL, and the standard deviation of the signal was less than 5%. The immunofluorescent probe and immunoassay system developed in this study are expected to be applicable not only to SARS-CoV-2 but also to the quantitative measurement of various other disease marker proteins and biomolecules.
RESUMEN
X-ray reflectometry (XRR), a surface-sensitive technique widely used for characterizing surfaces, buried interfaces, thin films, and multilayers, enables determination of the electron density distribution perpendicular to a well-defined surface specularly reflecting X-rays. However, the electron density distribution parallel to the surface cannot be determined from an X-ray reflectivity curve. The electron density correlation in the lateral direction is usually probed by measuring the grazing-incidence small-angle X-ray scattering (GISAXS). GISAXS measurement, however, typically requires using a collimated X-ray point beam to distinguish the GISAXS from the specularly reflected X-rays, and so the sample must be scanned in the lateral direction with the point beam to investigate variations in the surface and interface morphology for a region larger than the size of the beam. In this paper, we report a new approach based on X-ray grating interferometry: an X-ray sheet beam is used instead of an X-ray point beam. A method using this approach can simultaneously provide one-dimensional real-space images of X-ray reflectivity, surface curvature, and 'dark-field' contrast with a field-of-view of more than a few millimetres. As a demonstration, a sample having a 400 nm line and space SiO2 pattern with a depth of 10 nm on its surface was used, and the dark-field contrast due to the unresolved line and space structure, creating GISAXS in the lateral direction, was successfully observed. Quantitative analysis of these contrasts provided the real-space distribution of the structural parameters for a simple model of the grating structure. Our study paves the way to a new approach to structure analysis, providing a quantitative way to investigate real-space variations in surface and interface morphology through wavefront analysis.
RESUMEN
Several medical tools with various functions have been developed for minimally invasive diagnostics and treatment. Microfabrication techniques such as MEMS technology are useful for the realization of high-performance multifunctional minimally invasive medical tools with small sizes. An ultra-miniature pressure sensor and an intravascular ultrasonic forward-viewing imager have been developed as microsensors for use in the human body. Active bending catheters have been developed for steering catheter tips without using traction of wires from outside the body. An ultrasonic therapeutic tool for sonodynamic therapy and sonoporation, and a micro scanner for precise laser treatment have been developed as therapeutic tools for use in the human body. High-functionalized endoscopic tools and catheters will enable more precise and safe diagnostics and therapy, as well as novel diagnostics and treatment which have been impossible to date.