Name: microfluidic imaging flow cytometry by asymmetric-detection time-stretch optical microscopy (atom)
Uploaded: 2017-06-28T15:00:00
Description: Watch this Scientific Journal Video about Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy ATOM at JoVE.com

We thank Mr. P. Yeung for preparing the MCF-7 for us. This work was partially supported by grants from the Research Grant Council of the Hong Kong Special Administration Region, China (Project no. 17259316, 17207715, 17207714, 17205215, and HKU 720112E), the Innovation and Technology Support Programme (ITS/090/14), and the University Development Fund of HKU.

1. Sample Preparation
<ol>
	<li>Sample preparation (adherent cells; MCF-7 cells)
	<ol>
		<li>Take out the cell culture dish from the incubator and drain the culture medium.</li>
		<li>Rinse the cells on a dish with 1x phosphate-buffered saline (PBS) to remove excessive culture medium.</li>
		<li>Add 3 mL of a solution of 0.25% trypsin to the culture dish (diameter of 100 mm) and put it in a 37 &#176;C, 5% CO2 incubator for 4 min. 
		NOTE: The trypsin dissolves the adhesive protein of th...

<ol>
	<li>Lau, A. K. S., Wong, T. T. W., Shum, H. C., Wong, K. K. Y., Tsia, K. K., Barteneva, N. S., Vorobjev, I. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Imaging Flow Cytometry: Methods and Protocols. , 23-45 (2016).</li><li>Goda, K., Tsia, K. K., Jalali, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Serial+time-encoded+amplified+imaging+for+real-time+observation+of+fast+dynamic+phenomena.">Serial time-encoded amplified imaging for real-time observation of fast dynamic phenomena.</a> Nature. 458 (7242), 1145-1149 (2009).</li><li>Goda, K., Jalali, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dispersive+Fourier+transformation+for+fast+continuous+single-shot+measurements.">Dispersive Fourier transformation for fast continuous single-shot measurements.</a> Nat Photon. 7 (2), 102-112 (2013).</li><li>Lau, A. K., Shum, H. C., Wong, K. K., Tsia, K. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optofluidic+time-stretch+imaging+-+an+emerging+tool+for+high-throughput+imaging+flow+cytometry.">Optofluidic time-stretch imaging - an emerging tool for high-throughput imaging flow cytometry.</a> Lab Chip. 16 (10), 1743-1756 (2016).</li><li>Lau, A. K. S., Tang, A. H. L., Xu, J., Wong, X. W., Y, K. K., Tsia, K. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+Time+Stretch+for+High-Speed+and+High-Throughput+Imaging+-+From+Single-Cell+to+Tissue-Wide+Scales.">Optical Time Stretch for High-Speed and High-Throughput Imaging - From Single-Cell to Tissue-Wide Scales.</a> IEEE J. Sel. Top. in Quant. Electron. 22 (4), (2016).</li><li>Lei, C., Guo, B., Cheng, Z., Goda, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+time-stretch+imaging:+Principles+and+applications.">Optical time-stretch imaging: Principles and applications.</a> Appl Phys Rev. 3 (1), 011102 (2016).</li><li>Lei, C., Guo, B., Cheng, Z., Goda, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+time-stretch+imaging:+Principles+and+applications.">Optical time-stretch imaging: Principles and applications.</a> Applied Physics Reviews. 3 (011102), (2016).</li><li>Goda, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-throughput+single-microparticle+imaging+flow+analyzer.">High-throughput single-microparticle imaging flow analyzer.</a> Proc Natl Acad Sci U S A. 109 (29), 11630-11635 (2012).</li><li>Goda, K., Solli, D. R., Tsia, K. K., Jalali, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Theory+of+amplified+dispersive+Fourier+transformation.">Theory of amplified dispersive Fourier transformation.</a> Physical Review A. 80 (4), 043821 (2009).</li><li>Goda, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-throughput+single-microparticle+imaging+flow+analyzer.">High-throughput single-microparticle imaging flow analyzer.</a> Proc Natl Acad Sci U S A. 109 (29), 11630-11635 (2012).</li><li>Lai, Q. T. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-throughput+time-stretch+imaging+flow+cytometry+for+multi-class+classification+of+phytoplankton.">High-throughput time-stretch imaging flow cytometry for multi-class classification of phytoplankton.</a> Opt. Express. 24 (25), 28170-28184 (2016).</li><li>Chen, C. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deep+Learning+in+Label-free+Cell+Classification.">Deep Learning in Label-free Cell Classification.</a> Sci Rep. 6, 21471 (2016).</li><li>Fard, A. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nomarski+serial+time-encoded+amplified+microscopy+for+high-speed+contrast-enhanced+imaging+of+transparent+media.">Nomarski serial time-encoded amplified microscopy for high-speed contrast-enhanced imaging of transparent media.</a> Biomed Opt Express. 2 (12), 3387-3392 (2011).</li><li>Lau, A. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interferometric+time-stretch+microscopy+for+ultrafast+quantitative+cellular+and+tissue+imaging+at+1+mum.">Interferometric time-stretch microscopy for ultrafast quantitative cellular and tissue imaging at 1 mum.</a> J Biomed Opt. 19 (7), 76001 (2014).</li><li>Mahjoubfar, A., Chen, C., Niazi, K. R., Rabizadeh, S., Jalali, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Label-free+high-throughput+cell+screening+in+flow.">Label-free high-throughput cell screening in flow.</a> Biomed Opt Express. 4 (9), 1618-1625 (2013).</li><li>Wong, T. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Asymmetric-detection+time-stretch+optical+microscopy+(ATOM)+for+ultrafast+high-contrast+cellular+imaging+in+flow.">Asymmetric-detection time-stretch optical microscopy (ATOM) for ultrafast high-contrast cellular imaging in flow.</a> Sci Rep. 4, 3656 (2014).</li><li>Mata, T. M., Martins, A. A., Caetano, N. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microalgae+for+biodiesel+production+and+other+applications:+A+review.">Microalgae for biodiesel production and other applications: A review.</a> Renew Sustainable Energy Rev. 14 (1), 217-232 (2010).</li><li>Irigoien, X., Huisman, J., Harris, R. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+biodiversity+patterns+of+marine+phytoplankton+and+zooplankton.">Global biodiversity patterns of marine phytoplankton and zooplankton.</a> Nature. 429 (6994), 863-867 (2004).</li><li>Wei, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coherent+Laser+Source+for+High+Frame-Rate+Optical+Time-Stretch+Microscopy+at+1.0+&#181;m.">Coherent Laser Source for High Frame-Rate Optical Time-Stretch Microscopy at 1.0 &#181;m.</a> IEEE J. Sel. Top. Quantum Electron. 20 (5), 384-389 (2014).</li><li>Wei, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Breathing+laser+as+an+inertia-free+swept+source+for+high-quality+ultrafast+optical+bioimaging.">Breathing laser as an inertia-free swept source for high-quality ultrafast optical bioimaging.</a> Opt. Lett. 39 (23), 6593-6596 (2014).</li><li>Xu, Y., Wei, X., Ren, Z., Wong, K. K. Y., Tsia, K. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrafast+measurements+of+optical+spectral+coherence+by+single-shot+time-stretch+interferometry.">Ultrafast measurements of optical spectral coherence by single-shot time-stretch interferometry.</a> Sci Rep. 6, 27937 (2016).</li><li>Tsia, K. K., Goda, K., Capewell, D., Jalali, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+of+serial+time-encoded+amplified+microscope.">Performance of serial time-encoded amplified microscope.</a> Opt. Express. 18 (10), 10016-10028 (2010).</li><li>Alix-Panabi&#232;res, C., Pantel, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Challenges+in+circulating+tumour+cell+research.">Challenges in circulating tumour cell research.</a> Nat Rev Cancer. 14 (9), 623-631 (2014).</li><li>Kling, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Beyond+counting+tumor+cells.">Beyond counting tumor cells.</a> Nat Biotech. 30 (7), 578-580 (2012).</li><li>Hodgkinson, C. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumorigenicity+and+genetic+profiling+of+circulating+tumor+cells+in+small-cell+lung+cancer.">Tumorigenicity and genetic profiling of circulating tumor cells in small-cell lung cancer.</a> Nat Med. 20 (8), 897-903 (2014).</li><li>Ozkumur, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inertial+focusing+for+tumor+antigen-dependent+and+-independent+sorting+of+rare+circulating+tumor+cells.">Inertial focusing for tumor antigen-dependent and -independent sorting of rare circulating tumor cells.</a> Sci Transl Med. 5 (179), (2013).</li><li>Hou, H. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+retrieval+of+circulating+tumor+cells+using+centrifugal+forces.">Isolation and retrieval of circulating tumor cells using centrifugal forces.</a> Scientific Reports. 3, 1259 (2013).</li><li>Karabacak, N. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=marker-free+isolation+of+circulating+tumor+cells+from+blood+samples.">marker-free isolation of circulating tumor cells from blood samples.</a> Nat. Protocols. 9 (3), 694-710 (2014).</li><li>Krebs, M. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+analysis+of+circulating+tumour+cells-biology+and+biomarkers.">Molecular analysis of circulating tumour cells-biology and biomarkers.</a> Nat Rev Clin Oncol. 11 (3), 129-144 (2014).</li><li>Wu, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrafast+Laser-Scanning+Time-Stretch+Imaging+at+Visible+Wavelengths.">Ultrafast Laser-Scanning Time-Stretch Imaging at Visible Wavelengths.</a> Light Sci Appl. , (2016).</li></ol>

There are several technical details that require special attention during the ATOM system setup. First, it is essential to note that asymmetric/oblique spectrally-encoded illumination could introduce residual phase-gradient components (i.e., the shadowing effect) in the absorption contrast and influence the enhancement of phase-gradient contrast in ATOM. Therefore, this effect of oblique illumination should be minimized. Second, it should be emphasized that the time-multiplexing or time-interleaving schemeinvolv...

Optical imaging presents a powerful tool and cell-based assay to (almost) non-invasively visualize the detailed spatial distribution of many cellular/subcellular components, thus uncovering a multitude of morphological, biophysical, and biomolecular signatures of cells. However, this ability to extract high-content information from single cells has generally been compromised when an enormous and heterogeneous population of cells had to be investigated. This marks a common trade-off in cell-based assays between measurement throughput and content. A notable example is that adding imaging capability to flow cytometry has resulted in a down-scaling of throughput by at least 1-2 orders of magnitude compared to that of the classical non-imaging flow cytometers. Although it could offer complex morphological single-cell analysis that is not possible with standard flow cytometers1, imaging flow cytometry generally lacks sufficient throughput to identify cellular heterogeneity with high statistical confidence. This is necessary for new discoveries in biology and for gaining an understanding of the pathogenesis of diseases. The key technical challenge lies in the inherent speed limit imposed by the common optical imaging strategies: laser-beam scanning, (e.g., by galvanometric mirrors), and/or image sensors (e.g., charge-coupled device (CCD) and complementary metal-oxide semiconductor (CMOS)). The laser scanning speed is intrinsically restricted by the mechanical inertia of the scanning mirrors, whereas the frame rate of CCD or CMOS is limited by the fundamental trade-off between imaging speed and sensitivity (i.e., increasing the frame rate leads to reduced signal detection sensitivity, and vice versa).
Based on an all-optical, ultrafast image-encoding mechanism, optical time-stretch imaging has been demonstrated as an attractive platform for high-throughput imaging flow cytometers, without need of the conventional image sensors or mechanical laser scanning2,3. Detailed descriptions of the working principle of time-stretch imaging can be found in references4,5,6,7. In brief, it consists of two interchangeable mapping steps: (i) spectral encoding (wavelength-space mapping), in which the spatial coordinates of the imaged specimen are mapped to different wavelengths across the spectrum of the light-pulsed beam8,9, and (ii) a dispersive Fourier transformation (wavelength-time mapping)9, in which the wavelength components of individual laser pulses are transformed (stretched) via group velocity dispersion (GVD) into temporal (wavelength-swept) waveforms (Figure 1). An important feature of time-stretch imaging is optical amplification, which plays a critical role in combatting the loss of sensitivity due to ultrafast photodetection and GVD loss, thus enhancing the image signal-to-noise ratio (SNR) without being contaminated by the photodetector noise9. Since each laser pulse encodes a line-scan of the imaged specimen, which is orthogonal to the unidirectional flow of the cells, an effective line-scan rate is determined by the laser repetition rate, which is typically beyond 10 MHz. This ultrafast operation enables blur-free, single-cell image capture at a throughput of 10,000-100,000 cells/s (i.e., 10-100 times higher than conventional imaging flow cytometry). As a result, time-stretch imaging could find unique applications in high-throughput, single-cell, image-based screening, especially when there is a need for identifying unknown heterogeneity or rare/aberrant cells within a sizable population (thousands to millions of cells), such as rare cancer cell screening10 or micro-algae classification11.
Time-stretch imaging predominantly relies on bright-field (BF) image capture, from which the image contrast is generated through light scattering and absorption from the cells2,3,9,10,11. Such label-free, single-cell imaging capabilities could bypass the detrimental effects associated with the fluorescent labels, such as cytotoxicity and photobleaching, and yet provide valuable information for single-cell analysis based on the cellular and sub-cellular texture and morphology. These label-free parameters are proven to be effective for the deep image classification of cells, especially when an enormous cell population is available11,12. However, in many occasions, BF imaging fails to provide sufficient contrast to reveal the detailed morphology of the label-free transparent cells. Different label-free, phase-contrast, time-stretch imaging modalities have been developed for enhancing the imaging contrast at ultrafast frame rates13,14,15. Among these techniques, asymmetric-detection time-stretch optical microscopy (ATOM) was developed to reveal the phase-gradient (differential-interference-contrast-(DIC)-like) contrast based on a concept similar to Schlieren photography, enabling the label-free, high-contrast imaging of single cells at an ultrahigh microfluidic speed (up to 10 m/s)16. This effect can be readily generated through oblique detection or illumination by partially blocking the image-encoded beam path or tilting the beam before photodetection. Another advantage of ATOM is its ability to simultaneously acquire two phase-gradient contrasts along opposite orientations. Intensity subtraction and summation of two opposite-contrast images yield the differential phase-gradient contrast and the absorption contrast, respectively, from the same line-scan. This work presents a detailed protocol describing the implementation of ATOM, including the establishment of the optical setup, the sample preparation, and the data acquisition and visualization. Specifically, this work demonstrates the ATOM operation with single-cell imaging of human blood cells, cancer cells, and phytoplankton (microalgae). This highlights the applicability of ATOM to imaging flow cytometry, not only in the biomedical arena, but also in marine and biofuel research17,18.

<table border="0" cellpadding="0" cellspacing="0" width="789">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:207px;">Nikon Plan Fluorite Physiology Objectives 40X</td>
			<td style="width:71px;">Nikon</td>
			<td style="width:119px;">MRF07420</td>
			<td style="width:393px;">Objective lens (Obj2)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Olympus Plan Fluorite Objective, 0.75 NA, 0.51 mm WD, 40X</td>
			<td style="width:71px;">Olympus</td>
			<td>RMS40X-PF</td>
			<td>Objective lens (Obj1)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:207px;">N-BK7 Plano-Convex Lenses</td>
			<td style="width:71px;">Thorlabs</td>
			<td>LA1145-C</td>
			<td>For relaying spectral shower</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:207px;">FC/APC Fiber Collimation Package</td>
			<td style="width:71px;">Thorlabs</td>
			<td style="width:119px;">F220APC-1064</td>
			<td>For outputing and collecting laser pulses</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:207px;">Pellicle beamsplitter</td>
			<td style="width:71px;">Thorlabs</td>
			<td style="width:119px;">BP145B3</td>
			<td>For making beam replica</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:207px;">Protected silver mirror</td>
			<td style="width:71px;">Thorlabs</td>
			<td style="width:119px;">PF10-03-P01</td>
			<td>For reflecting light</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:207px;">800-1650nm 12GHz single mode DC-coupled NIR Photoreceiver</td>
			<td style="width:71px;">Newport</td>
			<td style="width:119px;">1544-B</td>
			<td>For converting light into electrical signal</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:207px;">Infiniium High-Performance Oscilloscope</td>
			<td style="width:71px;">Agilent</td>
			<td style="width:119px;">DSOX91604A</td>
			<td>To save the light-converted electrical signals</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:207px;">HI1060 optical fiber</td>
			<td style="width:71px;">Corning</td>
			<td style="width:119px;">HI1060</td>
			<td>Optical fiber for time-stretch</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:207px;">YTTERBIUM DOPED FIBER AMPLIFIER</td>
			<td style="width:71px;">Keopsys</td>
			<td style="width:119px;">KPS-STD-BT-YFA-37-BO-SM-111-FA-FA</td>
			<td>Optical in-line amplifier</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:207px;">Holographic grating</td>
			<td style="width:71px;">Wasatch Photonics</td>
			<td style="width:119px;">020305-6</td>
			<td>Grating</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:207px;">Infuse/Withdraw Syringe Pumps</td>
			<td style="width:71px;">Harvard Apparatus</td>
			<td style="width:119px;">PHD 2000</td>
			<td>Syringe pump for sample loading in micro-fluidic channels</td>
		</tr>
	</tbody>
</table>

microfluidic imaging flow cytometry by asymmetric-detection time-stretch optical microscopy (atom)

Scaling the number of measurable parameters, which allows for multidimensional data analysis and thus higher-confidence statistical results, has been the main trend in the advanced development of flow cytometry. Notably, adding high-resolution imaging capabilities allows for the complex morphological analysis of cellular/sub-cellular structures. This is not possible with standard flow cytometers. However, it is valuable for advancing our knowledge of cellular functions and can benefit life science research, clinical diagnostics, and environmental monitoring. Incorporating imaging capabilities into flow cytometry compromises the assay throughput, primarily due to the limitations on speed and sensitivity in the camera technologies. To overcome this speed or throughput challenge facing imaging flow cytometry while preserving the image quality, asymmetric-detection time-stretch optical microscopy (ATOM) has been demonstrated to enable high-contrast, single-cell imaging with sub-cellular resolution, at an imaging throughput as high as 100,000 cells/s. Based on the imaging concept of conventional time-stretch imaging, which relies on all-optical image encoding and retrieval through the use of ultrafast broadband laser pulses, ATOM further advances imaging performance by enhancing the image contrast of unlabeled/unstained cells. This is achieved by accessing the phase-gradient information of the cells, which is spectrally encoded into single-shot broadband pulses. Hence, ATOM is particularly advantageous in high-throughput measurements of single-cell morphology and texture &#8211; information indicative of cell types, states, and even functions. Ultimately, this could become a powerful imaging flow cytometry platform for the biophysical phenotyping of cells, complementing the current state-of-the-art biochemical-marker-based cellular assay. This work describes a protocol to establish the key modules of an ATOM system (from optical frontend to data processing and visualization backend), as well as the workflow of imaging flow cytometry based on ATOM, using human cells and micro-algae as the examples.

This work illustrates two single-cell imaging demonstrations by ATOM: one with mammalian cells (human peripheral blood mononuclear cells (PBMC) and breast cancer cells (MCF-7)) and another with phytoplanktons (Scenedesmus and Chlamydomonas). The first experiment was motivated by the growing interest in liquid biopsy for the detection, enumeration, and characterization of circulating tumor cells (CTCs) in the blood23. The ability to...

Watch this Scientific Journal Video about Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy ATOM at JoVE.com

Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy ATOM

This protocol describes the implementation of an asymmetric-detection time-stretch optical microscopy system for single-cell imaging in ultrafast microfluidic flow and its applications in imaging flow cytometry.

Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy (ATOM)

Scaling the number of measurable parameters, which allows for multidimensional data analysis and thus higher-confidence statistical results, has been the ...

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Underground storage permanence is a major concern for carbon capture and storage. Pumping CO2 into carbonate reservoirs has the potential to dissolve ...

Novel Photoacoustic Microscopy and Optical Coherence Tomography Dual-modality Chorioretinal Imaging in Living Rabbit Eyes

Photoacoustic ocular imaging is an emerging ophthalmic imaging technology that can noninvasively visualize ocular tissue by converting light energy into ...

Generation of Size-controlled Poly (ethylene Glycol) Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Generation of Size-controlled Poly ethylene Glycol Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. ...