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

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

Citation

The article is titled "Highly sensitive lens-free fluorescence imaging device enabled by a complementary combination of interference and absorption filters". It was written by Kiyotaka Sasagawa, Ayaka Kimura, Makito Haruta, Toshihiko Noda, Takashi Tokuda, and Jun Ohta. The authors are from the Division of Materials Science, Graduate School of Science and Technology, Nara Institute of Science and Technology in Nara, Japan. This article was published in Biomedical Optics Express. The article appears in Volume 9, Number 9 of the journal, published on September 1, 2018. More specifically, this article spans pages 4329-4344 in the journal.

Keywords

  • Lens-free imaging
  • Fluorescence imaging
  • Emission filter
  • Interference filter
  • Absorption filter
  • Fiber optic plate (FOP)
  • Sensitivity
  • Excitation light rejection
  • Auto-fluorescence
  • Spatial resolution
  • Time-lapse imaging
  • Cell culturing
  • Point-of-care assay
  • Hybrid filter

Brief

The article "Highly sensitive lens-free fluorescence imaging device enabled by a complementary combination of interference and absorption filters" was published in Biomedical Optics Express on September 1, 2018. The authors are Kiyotaka Sasagawa, Ayaka Kimura, Makito Haruta, Toshihiko Noda, Takashi Tokuda, and Jun Ohta.

Summary

lens-free fluorescence imaging device uses a hybrid filter, composed of an interference filter and an absorption filter, to address challenges in lens-free fluorescence imaging. The device achieves an excitation rejection ratio of 108:1 and a spatial resolution of 12 µm.

Challenges of Conventional Lens-Free Fluorescence Imaging

  • Interference filters, while commonly used in fluorescence microscopes, suffer from a shifted transmission spectrum depending on the incident angle of light. This effect is particularly problematic when imaging samples like cells containing GFP, where excitation and emission peaks are close. Scattered light, often more intense than the fluorescence signal, can pass through the filter, reducing its effectiveness.
  • Absorption filters offer angle-independent transmission but are hampered by auto-fluorescence. In lens-free systems, this auto-fluorescence, particularly prominent at high excitation light intensities, limits the achievable rejection performance.

Hybrid Filter: A Solution

The hybrid filter combines an interference filter and an absorption filter, connected by a fiber optic plate (FOP), directly above an image sensor. This combination leverages the strengths of each filter type:

  • The interference filter, with low auto-fluorescence, reflects scattered light.
  • The absorption filter then absorbs this reflected light, minimizing the overall auto-fluorescence.

Advantages of the Hybrid Filter

  • Significantly improved fluorescence imaging performance: The hybrid filter demonstrates a 1000-fold improvement in effective transmittance compared to an absorption filter alone, achieving a transmittance of approximately 10-8.
  • Compatibility with bright-field lens-free imaging techniques: The flat surface of the hybrid filter allows for integration with bright-field imaging methods, enabling dual-mode imaging capabilities.

Experimental Validation

The hybrid filter's effectiveness is validated through imaging experiments:

  • Fluorescent film pattern: Images acquired using the hybrid filter exhibit superior contrast and clarity compared to those obtained using individual interference or absorption filters.
  • Fluorescent beads: The hybrid filter effectively reduces background noise, enhancing the visibility of fluorescent beads.
  • Time-lapse imaging of living cells: The device's compact size allows for time-lapse imaging of HEK293 cells within a CO2 incubator, demonstrating its potential for live-cell studies.

The hybrid filter design represents a significant advancement in lens-free fluorescence imaging, offering a path toward developing compact, high-performance devices suitable for various applications, including point-of-care diagnostics and live-cell imaging.

Origin: https://www.semanticscholar.org/paper/Highly-sensitive-lens-free-fluorescence-imaging-by-Sasagawa-Kimura/454fb5bfa4609f9607b10b256f488fc9880d758e
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