18 March 2014 Dual-mode lensless imaging device for digital enzyme linked immunosorbent assay
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Abstract
Digital enzyme linked immunosorbent assay (ELISA) is an ultra-sensitive technology for detecting biomarkers and viruses etc. As a conventional ELISA technique, a target molecule is bonded to an antibody with an enzyme by antigen-antibody reaction. In this technology, a femto-liter droplet chamber array is used as reaction chambers. Due to its small volume, the concentration of fluorescent product by single enzyme can be sufficient for detection by a fluorescent microscopy. In this work, we demonstrate a miniaturized lensless imaging device for digital ELISA by using a custom image sensor. The pixel array of the sensor is coated with a 20 μm-thick yellow filter to eliminate excitation light at 470 nm and covered by a fiber optic plate (FOP) to protect the sensor without resolution degradation. The droplet chamber array formed on a 50μm-thick glass plate is directly placed on the FOP. In the digital ELISA, microbeads coated with antibody are loaded into the droplet chamber array, and the ratio of the fluorescent to the non-fluorescent chambers with the microbeads are observed. In the fluorescence imaging, the spatial resolution is degraded by the spreading through the glass plate because the fluorescence is irradiated omnidirectionally. This degradation is compensated by image processing and the resolution of ~35 μm was achieved. In the bright field imaging, the projected images of the beads with collimated illumination are observed. By varying the incident angle and image composition, microbeads were successfully imaged.
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Kiyotaka Sasagawa, Kiyotaka Sasagawa, Soo Heyon Kim, Soo Heyon Kim, Kazuya Miyazawa, Kazuya Miyazawa, Hironari Takehara, Hironari Takehara, Toshihiko Noda, Toshihiko Noda, Takashi Tokuda, Takashi Tokuda, Ryota Iino, Ryota Iino, Hiroyuki Noji, Hiroyuki Noji, Jun Ohta, Jun Ohta, } "Dual-mode lensless imaging device for digital enzyme linked immunosorbent assay", Proc. SPIE 8933, Frontiers in Biological Detection: From Nanosensors to Systems VI, 89330N (18 March 2014); doi: 10.1117/12.2039948; https://doi.org/10.1117/12.2039948
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