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Subhead: A novel hybrid bright/dark-field transport of intensity (HBDTI) approach for high-throughput quantitative phase microscopy shows potential for delineating subcellular structures in large-scale cell studies.

Recently, the Smart Computational Imaging Laboratory (SCILab) of the School of Electronic and Optical Engineering of Nanjing University of Science and Technology and researchers from the University of Hong Kong published a research paper entitled "Hybrid brightfield and darkfield transport of intensity approach for high throughput quantitative phase microscopy" on the top optical journal Advanced Photonics. Linpeng Lu, a doctoral student from our university, and Jiaji Li, a postdoctoral fellow, are the co-first authors of this paper. Professor Chao Zuo and Professor Qian Chen from our university and Professor Edmund Y. Lam from Hong Kong University are the co-corresponding authors of this paper.

Article link: https://doi.org/10.1117/1.AP.4.5.056002

A hybrid bright/dark-field transport of intensity (HBDTI) approach for high-throughput quantitative phase microscopy significantly expands the space-bandwidth-product of a conventional microscope, extending the accessible sample spatial frequencies in the Fourier space well beyond the traditional coherent diffraction limit. Image credit: Linpeng Lu, NJUST.

Cell organelles are involved in a variety of cellular life activities. Their dysfunction is closely related to the development and metastasis of cancer. Exploration of subcellular structures and their abnormal states facilitates insights into the mechanisms of pathologies, which may enable early diagnosis for more effective treatment.

Fig. 1 Application requirements in key areas of cell research (materials are from the network)

The optical microscope, invented more than 400 years ago, has become an indispensable and ubiquitous instrument for investigating microscale objects in many areas of science and technology. In particular, fluorescence microscopy has achieved several leaps – from 2D wide-field to 3D confocal and then to super-resolution fluorescence microscopy, greatly promoting the development of modern life sciences.

Using conventional microscopes, researchers currently struggle to generate sufficient intrinsic contrast for unstained cells due to their low absorption or weak scattering properties. Specific dyes or fluorescent labels can help with visualization, but long-term observation of live cells remains difficult.

Fig. 2 Limitations of traditional optical microscopes (materials are from the network)

Recently, quantitative phase imaging (QPI) has shown promise with its unique ability to quantify the phase delay of unlabeled specimens in a non-destructive way. Yet the throughput of an imaging platform is fundamentally limited by its optical system’s space-bandwidth product (SBP), and the SBP increase of a microscope is fundamentally confounded by the scale-dependent geometric aberrations of its optical elements. This results in a tradeoff between achievable image resolution and field of view (FOV).

An approach to achieving label-free, high-resolution, and large FOV microscopic imaging is needed to enable precise detection and quantitative analysis of subcellular features and events. To this end, researchers from Nanjing University of Science and Technology (NJUST) and the University of Hong Kong recently developed a label-free high-throughput microscopy method based on hybrid brightfield and darkfield illuminations. As reported in Advanced Photonics, the “hybrid brightfield-darkfield transport of intensity” (HBDTI) approach for high-throughput quantitative phase microscopy significantly expands the accessible sample spatial frequencies in the Fourier space, extending the maximum achievable resolution by approximately fivefold over the coherent imaging diffraction limit.

Fig. 3 The physical diagram and the schematic diagram of the optical system

Based on the principle of illumination multiplexing and synthetic aperture, they establish a forward imaging model of nonlinear brightfield and darkfield intensity transport. This model endows HBDTI with the ability to provide features beyond the coherent diffraction limit. Using a commercial microscope with a 4x, 0.16NA objective lens, the team demonstrated HBDTI high-throughput imaging, attaining 488-nm half-width imaging resolution within a FOV of approximately 7.19 mm², yielding a 25× increase in SBP over the case of coherent illumination.

Fig. 4 Roadmap of the proposed HBDTI method

Noninvasive high-throughput imaging provides the possibility for delineating subcellular structures in large-scale cell studies. HBDTI reportedly offers a simple, high-performance, low-cost, and universal imaging tool for quantitative analysis in life sciences and biomedical research. The corresponding author Chao Zuo, principal investigator of the Smart Computational Imaging Laboratory (SCILab) at NJUST, remarks, “Given its capability for high-throughput QPI, the proposed HBDTI approach is expected to provide a novel and powerful solution for cross-scale detection and analysis of subcellular structures in a large number of cell clusters.” Zuo notes that further efforts are needed to promote the high-speed implementation of HBDTI in large-group live cell analysis.

Fig. 5 HBDTI high-throughput QPI results of blood smear

Fig. 6 HBDTI high-throughput QPI results of unlabeled HeLa cells

Finally, it is worth mentioning that this work has received extensive attention from domestic and foreign media, as well as news from SPIE Newsroom and reports from many media (phys.org, Newsachieve.com, AZO OPTIMS, etc.). In addition, the team organically combined "scientific research achievements" with "hand painting art". Linpeng Lu, the first author of the paper, boldly and creatively created a hand-painting video to illustrate the core idea of the method vividly.

Video link: https://spie.org/news/high-throughput-computational-microscopy-imaging

Fig. 7 Reported by SPIE Newsroom, phys.org, Newsachieve Com, AZO OPTIMS, etc.

This work was supported by the National Natural Science Foundation of China (61905115, 62105151, 62175109, and U21B2033), Leading Technology of Jiangsu Basic Research Plan (BK20192003), Youth Foundation of Jiangsu Province (BK20190445, BK20210338), Fundamental Research Funds for the Central Universities (30920032101), and Open Research Fund of Jiangsu Key Laboratory of Spectral Imaging and Intelligent Sense (JSGP202105).

来源 | 南理工官网

排版 | 孙菲

复审 | 左超

终审 | 徐峰