CMOS image sensor-based ELISA detector using lens-free shadow imaging platform

This paper presents a compact and cost-effective lens-free complementary metal-oxide-semiconductor (CMOS) image sensor based bacterial cell detection platform that can measure colorimetric light signals in the enzyme linked immunosorbent assay (ELISA) process. In this work, we first demonstrate the CMOS image sensor based shadow imaging platform as an ELISA detector and provide critical performance data that show this platform to be comparable or even better than that of a commercial ELISA reader. To evaluate the efficacy of the shadow imaging platform-based ELISA detector as a practical approach, the pathogenic bacteria Listeria monocytogenes (L. monocytogenes) and Salmonella typhimurium (S. typhimurium) were utilized within a conventional 96-well plate. To reduce the noise signal from unwanted particles and light scattering, a custom-made aperture cover and image processing procedures were developed. Because this platform employs a multi-million pixel CMOS image sensor enabling effective removal of noise signals that can not be achieved with a single pixel detector, i.e., conventional ELISA reader, it can perform more reproducible ELISA measurement. Combined with the shadow imaging technique, this approach holds great promise in many applications including blood analysis, pathogen detection, and environmental monitoring.