Highly sensitive lens-free fluorescence imaging device enabled by a complementary combination of interference and absorption filters

Abstract

We report a lens-free fluorescence imaging device using a composite filter composed of an interference filter and an absorption filter, each applied to one side of a fiber optic plate (FOP). The transmission of angled excitation light through the interference filter is absorbed by the absorption filter. The auto-fluorescence of the absorption filter is reduced by the reflection from the interference filter of normally incident excitation light. As a result, high-performance rejection of excitation light is achieved in a lens-free device. The FOP provides a flat, hard imaging device surface that does not degrade the spatial resolution. We demonstrate excitation rejection of approximately 108:1 at a wavelength of 450 nm in a fabricated lens-free device. The resolution of fluorescence imaging is approximately 12 µm. Time-lapse imaging of cells containing green fluorescent protein was performed in a 5-µm thin-film chamber. The small dimensions of the device allow observation of cell culturing in a CO2 incubator. We also demonstrate that the proposed lens-free filter is compatible with super-resolution bright-field imaging techniques. These features open a way to develop a high-performance, dual-mode, lens-free imaging device that is expected to be a powerful tool for many applications, such as imaging of labeled cells and point-of-care assay.

Optical Imaging Approaches to Monitor Static and Dynamic Cell‐on‐Chip Platforms: A Tutorial Review

“…For more information about methods to maintain the health parameters in short term and long term imaging, the reader is referred to another reference . An example use of the equipment related to the cells‐health in optical imaging is the work reported by Sasagawa et al where they kept their imaging device in a CO 2 incubator during cell culturing for a time‐laps imaging . Another example is the work reported by Yissachar et al where they utilized a heating block for another time‐laps imaging of their organ culture system …”

“…[26] An example use of the equipment related to the cells-health in optical imaging is the work reported by Sasagawa et al where they kept their imaging device in a CO 2 incubator during cell culturing for a time-laps imaging. [27] Another example is the work reported by Yissachar et al where they utilized a heating block for another time-laps imaging of their organ culture system. [28] In 2D cell cultures, the minimum light diffraction and diffusion allows a perfect collection of the microscopic images.…”

Lens-free Dual-color Fluorescent CMOS Image Sensor for F?rster Resonance Energy Transfer Imaging

“…A lens-free imaging system is expected to be used in new applications in bio-imaging. (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) This is because a conventional fluorescence microscope is large, bulky, costly, and has a limited field of view. (4,7) A lens-free imaging system, on the other hand, does not include any lenses in its design.…”

“…(4,7,9) Previous research has already shown that the fabrication of small yet high-resolution image sensors is possible for various purposes, such as observing the brain activity of rodents, (15) illuminating and detecting light in deep biological tissues for optical therapy and diagnosis, (16) and optogenetics. (17) Moreover, it is possible to insert a small image sensor in an incubator to observe cultured cells for a long period of time, (3,6,8,11,12) and also possible to develop a similar image sensor for long-term Förster resonance energy transfer (FRET) observation in a small animal.…”

“…Generally, these filters block excitation light and transmit the target fluorescent light. However, utilizing an interference filter in a lens-free setup will cause the transmission spectrum to shift to a lower wavelength when the incident light is not normal, (25) while the absorption filter will usually emit fluorescence that is outside of the rejection band of the absorption filter, (11,12) which might affect the results of experiments.…”