Compact lensless digital counting system for fluorescent micro-reaction-chamber array

摘要

A compact system proposed here is designed primarily for a digital enzyme-linked immunosorbent assay (ELISA). Conventional digital ELISA systems require a fluorescence microscope for counting of a fluorescent micro-reaction-chamber array with or without fluorescence in order to determine the concentration of the target proteins. Our proposed system is compact as it does not use lens optics. The system consists of an array of micro-light pipes dedicated to image the fluorescence of micro-reaction chambers, and a CMOS image sensor that is attached directly to the exit of the micro-light pipes. The micro-light pipes are made of electroplated metal and filled with yellow dye-doped resin. This construction causes excitation light to be eliminated and only fluorescence to be transmitted effectively to a detector. We found that the angled irradiation of a narrow-band excitation light source was suitable for our system. We used a stacked photodiode image sensor that can discriminate colors without coating color filters. The sensitivity and the image quality of our new sensor were improved significantly by introducing a floating diffusion amplifier in each pixel. We also discussed a methodology for counting micro-reaction chambers with fluorescence through an experimental enzyme assay.