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Zong H, Yurdakul C, Zhao J, Wang Z, Chen F, Ünlü MS, Cheng JX. Bond-selective full-field optical coherence tomography. OPTICS EXPRESS 2023; 31:41202-41218. [PMID: 38087525 DOI: 10.1364/oe.503861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 11/10/2023] [Indexed: 12/18/2023]
Abstract
Optical coherence tomography (OCT) is a label-free, non-invasive 3D imaging tool widely used in both biological research and clinical diagnosis. Conventional OCT modalities can only visualize specimen tomography without chemical information. Here, we report a bond-selective full-field OCT (BS-FF-OCT), in which a pulsed mid-infrared laser is used to modulate the OCT signal through the photothermal effect, achieving label-free bond-selective 3D sectioned imaging of highly scattering samples. We first demonstrate BS-FF-OCT imaging of 1 µm PMMA beads embedded in agarose gel. Next, we show 3D hyperspectral imaging of up to 75 µm of polypropylene fiber mattress from a standard surgical mask. We then demonstrate BS-FF-OCT imaging on biological samples, including cancer cell spheroids and C. elegans. Using an alternative pulse timing configuration, we finally demonstrate the capability of BS-FF-OCT on imaging a highly scattering myelinated axons region in a mouse brain tissue slice.
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2
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Hamidi A, Bayhaqi YA, Canbaz F, Navarini AA, Cattin PC, Zam A. Towards phase-sensitive optical coherence tomography in smart laser osteotomy: temperature feedback. Lasers Med Sci 2023; 38:222. [PMID: 37752387 PMCID: PMC10522524 DOI: 10.1007/s10103-023-03886-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Accepted: 09/17/2023] [Indexed: 09/28/2023]
Abstract
Thermal effects during bone surgery pose a common challenge, whether using mechanical tools or lasers. An irrigation system is a standard solution to cool the tissue and reduce collateral thermal damage. In bone surgery using Er:YAG laser, insufficient irrigation raises the risk of thermal damage, while excessive water lowers ablation efficiency. This study investigated the potential of optical coherence tomography to provide feedback by relating the temperature rise with the photo-thermal expansion of the tissue. A phase-sensitive optical coherence tomography system (central wavelength of λ=1.288 μm, a bandwidth of 60.9 nm and a sweep rate of 104.17 kHz) was integrated with an Er:YAG laser using a custom-made dichromatic mirror. Phase calibration was performed by monitoring the temperature changes (thermal camera) and corresponding cumulative phase changes using the phase-sensitive optical coherence tomography system during laser ablation. In this experiment, we used an Er:YAG laser with 230 mJ per pulse at 10 Hz for ablation. Calibration coefficients were determined by fitting the temperature values to phase later and used to predict the temperature rise for subsequent laser ablations. Following the phase calibration step, we used the acquired values to predict the temperature rise of three different laser-induced cuts with the same parameters of the ablative laser. The average root-mean-square error for the three experiments was measured to be around 4 °C. In addition to single-point prediction, we evaluated this method's performance to predict the tissue's two-dimensional temperature rise during laser osteotomy. The findings suggest that the proposed principle could be used in the future to provide temperature feedback for minimally invasive laser osteotomy.
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Affiliation(s)
- Arsham Hamidi
- Biomedical Laser and Optics Group (BLOG), Department of Biomedical Engineering, University of Basel, CH-4123, Allschwil, Switzerland.
| | - Yakub A Bayhaqi
- Biomedical Laser and Optics Group (BLOG), Department of Biomedical Engineering, University of Basel, CH-4123, Allschwil, Switzerland
| | - Ferda Canbaz
- Biomedical Laser and Optics Group (BLOG), Department of Biomedical Engineering, University of Basel, CH-4123, Allschwil, Switzerland
| | - Alexander A Navarini
- Digital Dermatology, Department of Biomedical Engineering, University of Basel, CH-4123, Allschwil, Switzerland
| | - Philippe C Cattin
- Center for Medical Image Analysis and Navigation (CIAN), Department of Biomedical Engineering, University of Basel, CH-4123, Allschwil, Switzerland
| | - Azhar Zam
- Biomedical Laser and Optics Group (BLOG), Department of Biomedical Engineering, University of Basel, CH-4123, Allschwil, Switzerland
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, 129188, UAE
- Tandon School of Engineering, New York University, Brooklyn, NY, 11201, USA
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3
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Tanjaya NK, Toda K, Ideguchi T, Ishii S. Thermo-optical measurements using quantitative phase microscopy. OPTICS LETTERS 2023; 48:3311-3314. [PMID: 37319089 DOI: 10.1364/ol.489182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 05/18/2023] [Indexed: 06/17/2023]
Abstract
Quantitative phase microscopy (QPM) literally images the quantitative phase shift associated with image contrast, where the phase shift can be altered by laser heating. In this study, the thermal conductivity and thermo-optic coefficient (TOC) of a transparent substrate are simultaneously determined by measuring the phase difference induced by an external heating laser using a QPM setup. The substrates are coated with a 50-nm-thick titanium nitride film to photothermally generate heat. Then, the phase difference is semi-analytically modeled based on the heat transfer and thermo-optic effect to simultaneously extract the thermal conductivity and TOC. The measured thermal conductivity and TOC agree reasonably well, indicating the potential for measuring the thermal conductivities and TOCs of other transparent substrates. The concise setup and simple modeling differentiate the advantages of our method from other techniques.
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Veysset D, Ling T, Zhuo Y, Pandiyan VP, Sabesan R, Palanker D. Interferometric imaging of thermal expansion for temperature control in retinal laser therapy. BIOMEDICAL OPTICS EXPRESS 2022; 13:728-743. [PMID: 35284191 PMCID: PMC8884207 DOI: 10.1364/boe.448803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/27/2021] [Accepted: 12/28/2021] [Indexed: 06/14/2023]
Abstract
Precise control of the temperature rise is a prerequisite for proper photothermal therapy. In retinal laser therapy, the heat deposition is primarily governed by the melanin concentration, which can significantly vary across the retina and from patient to patient. In this work, we present a method for determining the optical and thermal properties of layered materials, directly applicable to the retina, using low-energy laser heating and phase-resolved optical coherence tomography (pOCT). The method is demonstrated on a polymer-based tissue phantom heated with a laser pulse focused onto an absorbing layer buried below the phantom's surface. Using a line-scan spectral-domain pOCT, optical path length changes induced by the thermal expansion were extracted from sequential B-scans. The material properties were then determined by matching the optical path length changes to a thermo-mechanical model developed for fast computation. This method determined the absorption coefficient with a precision of 2.5% and the temperature rise with a precision of about 0.2°C from a single laser exposure, while the peak did not exceed 8°C during 1 ms pulse, which is well within the tissue safety range and significantly more precise than other methods.
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Affiliation(s)
- David Veysset
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA
- Department of Ophthalmology, Stanford University, Stanford, CA 94305, USA
| | - Tong Ling
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA
- Department of Ophthalmology, Stanford University, Stanford, CA 94305, USA
- Present address: School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637457, Singapore
| | - Yueming Zhuo
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA
- Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA
| | | | - Ramkumar Sabesan
- Department of Ophthalmology, University of Washington, Seattle, WA 98109, USA
| | - Daniel Palanker
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA
- Department of Ophthalmology, Stanford University, Stanford, CA 94305, USA
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5
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Hu C, Kandel ME, Lee YJ, Popescu G. Synthetic aperture interference light (SAIL) microscopy for high-throughput label-free imaging. APPLIED PHYSICS LETTERS 2021; 119:233701. [PMID: 34924588 PMCID: PMC8660142 DOI: 10.1063/5.0065628] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 11/29/2021] [Indexed: 05/07/2023]
Abstract
Quantitative phase imaging (QPI) is a valuable label-free modality that has gained significant interest due to its wide potentials, from basic biology to clinical applications. Most existing QPI systems measure microscopic objects via interferometry or nonlinear iterative phase reconstructions from intensity measurements. However, all imaging systems compromise spatial resolution for the field of view and vice versa, i.e., suffer from a limited space bandwidth product. Current solutions to this problem involve computational phase retrieval algorithms, which are time-consuming and often suffer from convergence problems. In this article, we presented synthetic aperture interference light (SAIL) microscopy as a solution for high-resolution, wide field of view QPI. The proposed approach employs low-coherence interferometry to directly measure the optical phase delay under different illumination angles and produces large space-bandwidth product label-free imaging. We validate the performance of SAIL on standard samples and illustrate the biomedical applications on various specimens: pathology slides, entire insects, and dynamic live cells in large cultures. The reconstructed images have a synthetic numeric aperture of 0.45 and a field of view of 2.6 × 2.6 mm2. Due to its direct measurement of the phase information, SAIL microscopy does not require long computational time, eliminates data redundancy, and always converges.
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De la Torre I MH, Frausto-Rea GDR, Mendoza-Santoyo F, Del S Hernandez Montes M. Fish swim water bulk displacement visualization with digital holographic interferometry. APPLIED OPTICS 2021; 60:5376-5381. [PMID: 34263775 DOI: 10.1364/ao.425059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 05/24/2021] [Indexed: 06/13/2023]
Abstract
A collimated transmission beam interferometer is used to measure the water motion provoked by the fish swimming through it. An indirect measurement of the fish motion impact in the water contained in a home-type aquarium is detected. Measurements of the whole aquarium are possible due to a large diameter collimated laser beam in the interferometer's object arm. This beam goes through the aquarium, and any perturbation inside it deflects the collimated beam. The interferometer detects a phase difference, i.e., the beam through the disturbed water undergoes different optical paths. This optical phase change was first demonstrated by means of a simple test using spherical steel marbles placed in a cuvette. For this, the small water movements for a single steel marble are detected with the acquired optical phase. Next, the aquarium optical phase results show water movements according to the fishes' size and swimming speed. It is worth mentioning that no additives were added to the aquarium's fresh water during the tests, so the water was crystal clear.
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Boyle KC, Chen ZC, Ling T, Pandiyan VP, Kuchenbecker J, Sabesan R, Palanker D. Mechanisms of Light-Induced Deformations in Photoreceptors. Biophys J 2020; 119:1481-1488. [PMID: 33031739 PMCID: PMC7642315 DOI: 10.1016/j.bpj.2020.09.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 09/02/2020] [Accepted: 09/08/2020] [Indexed: 01/11/2023] Open
Abstract
Biological cells deform on a nanometer scale when their transmembrane voltage changes, an effect that has been visualized during the action potential using quantitative phase imaging. Similar changes in the optical path length have been observed in photoreceptor outer segments after a flash stimulus via phase-resolved optical coherence tomography. These optoretinograms reveal a fast, millisecond-scale contraction of the outer segments by tens of nanometers, followed by a slow (hundreds of milliseconds) elongation reaching hundreds of nanometers. Ultrafast measurements of the contractile response using line-field phase-resolved optical coherence tomography show a logarithmic increase in amplitude and a decreasing time to peak with increasing stimulus intensity. We present a model that relates the early receptor potential to these deformations based on the voltage-dependent membrane tension-the mechanism observed earlier in neurons and other electrogenic cells. The early receptor potential is caused by conformational changes in opsins after photoisomerization, resulting in the fractional shift of the charge across the disk membrane. Lateral repulsion of the ions on both sides of the membrane affects its surface tension and leads to its lateral expansion. Because the volume of the disks does not change on a millisecond timescale, their lateral expansion leads to an axial contraction of the outer segment. With increasing stimulus intensity and the resulting tension, the area expansion coefficient of the disk membrane also increases as thermally induced fluctuations are pulled flat, resisting further expansion. This leads to the logarithmic saturation observed in measurements as well as the peak shift in time. This imaging technique therefore relates the structural changes in the photoreceptor to the underlying neurological function of transducing light into electrical signals. Such label-free optical monitoring of neural activity using fast interferometry may be applicable not only to optoretinography but also to neuroscience in general.
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Affiliation(s)
- K C Boyle
- Department of Electrical Engineering, Stanford University, Stanford, California; Hansen Experimental Physics Laboratory, Stanford University, Stanford, California.
| | - Z C Chen
- Department of Electrical Engineering, Stanford University, Stanford, California; Hansen Experimental Physics Laboratory, Stanford University, Stanford, California
| | - T Ling
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California; Department of Ophthalmology, Stanford University, Stanford, California
| | - V P Pandiyan
- Department of Ophthalmology, University of Washington, Seattle, Washington
| | - J Kuchenbecker
- Department of Ophthalmology, University of Washington, Seattle, Washington
| | - R Sabesan
- Department of Ophthalmology, University of Washington, Seattle, Washington.
| | - D Palanker
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California; Department of Ophthalmology, Stanford University, Stanford, California.
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Ling T, Boyle KC, Zuckerman V, Flores T, Ramakrishnan C, Deisseroth K, Palanker D. High-speed interferometric imaging reveals dynamics of neuronal deformation during the action potential. Proc Natl Acad Sci U S A 2020; 117:10278-10285. [PMID: 32341158 PMCID: PMC7229674 DOI: 10.1073/pnas.1920039117] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Neurons undergo nanometer-scale deformations during action potentials, and the underlying mechanism has been actively debated for decades. Previous observations were limited to a single spot or the cell boundary, while movement across the entire neuron during the action potential remained unclear. Here we report full-field imaging of cellular deformations accompanying the action potential in mammalian neuron somas (-1.8 to 1.4 nm) and neurites (-0.7 to 0.9 nm), using high-speed quantitative phase imaging with a temporal resolution of 0.1 ms and an optical path length sensitivity of <4 pm per pixel. The spike-triggered average, synchronized to electrical recording, demonstrates that the time course of the optical phase changes closely matches the dynamics of the electrical signal. Utilizing the spatial and temporal correlations of the phase signals across the cell, we enhance the detection and segmentation of spiking cells compared to the shot-noise-limited performance of single pixels. Using three-dimensional (3D) cellular morphology extracted via confocal microscopy, we demonstrate that the voltage-dependent changes in the membrane tension induced by ionic repulsion can explain the magnitude, time course, and spatial features of the phase imaging. Our full-field observations of the spike-induced deformations shed light upon the electromechanical coupling mechanism in electrogenic cells and open the door to noninvasive label-free imaging of neural signaling.
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Affiliation(s)
- Tong Ling
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305;
- Department of Ophthalmology, Stanford University, Stanford, CA 94305
| | - Kevin C Boyle
- Department of Electrical Engineering, Stanford University, Stanford, CA 94305;
| | - Valentina Zuckerman
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305
| | - Thomas Flores
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305
| | | | - Karl Deisseroth
- Department of Bioengineering, Stanford University, Stanford, CA 94305
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305
| | - Daniel Palanker
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305;
- Department of Ophthalmology, Stanford University, Stanford, CA 94305
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9
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Flizikowski GAS, Capeloto OA, Camargo VG, Anghinoni B, Baesso ML, Malacarne LC, Belançon MP, Požar T, Astrath NGC. Laser induced thermoelastic surface displacement in solids detected simultaneously by photothermal mirror and interferometry. OPTICS EXPRESS 2020; 28:7116-7124. [PMID: 32225946 DOI: 10.1364/oe.386344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 02/10/2020] [Indexed: 06/10/2023]
Abstract
We propose a combined pump-probe optical method to investigate heat diffusion properties of solids. We demonstrate single-shot simultaneous laser-induced thermoelastic surface displacement of metals detected by concurrent measurements using photothermal mirror and interferometry. Both methods probe the surface displacement by analyzing the wavefront distortions of the probe beams reflected from the surface of the sample. Thermoelastic properties are retrieved by transient analysis in combination with numerical description of the thermoelastic displacement and temperature rise in the sample and in the surrounding air. This technique presents a capability for material characterization that can be extended to experiments for quantitative surface mapping.
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10
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Messner A, Werkmeister RM, Seidel G, Stegmann H, Schmetterer L, Aranha Dos Santos V. Light-induced changes of the subretinal space of the temporal retina observed via optical coherence tomography. Sci Rep 2019; 9:13632. [PMID: 31541190 PMCID: PMC6754376 DOI: 10.1038/s41598-019-50057-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 09/04/2019] [Indexed: 02/08/2023] Open
Abstract
Photoreceptor function is impaired in many retinal diseases like age-related macular degeneration. Currently, assessment of the photoreceptor function for the early diagnosis and monitoring of these diseases is either subjective, as in visual field testing, requires contact with the eye, like in electroretinography, or relies on research prototypes with acquisition speeds unattained by conventional imaging systems. We developed an objective, noncontact method to monitor photoreceptor function using a standard optical coherence tomography system. This method can be used with various white light sources for stimulation. The technique was applied in five volunteers and detected a decrease of volume of the subretinal space associated with light adaptation processes of the retina.
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Affiliation(s)
- Alina Messner
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, 1090, Vienna, Austria
| | - René M Werkmeister
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, 1090, Vienna, Austria
| | - Gerald Seidel
- Department of Ophthalmology, Medical University of Graz, 8036, Graz, Austria
| | - Hannes Stegmann
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, 1090, Vienna, Austria.,Christian Doppler Laboratory for Ocular and Dermal Effects of Thiomers, Medical University of Vienna, 1090, Vienna, Austria
| | - Leopold Schmetterer
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, 1090, Vienna, Austria.,Department of Clinical Pharmacology, Medical University of Vienna, 1090, Vienna, Austria.,Singapore Eye Research Institute, The Academia, Singapore, 169856, Singapore.,Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 636921, Singapore
| | - Valentin Aranha Dos Santos
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, 1090, Vienna, Austria.
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Zhang D, Lan L, Bai Y, Majeed H, Kandel ME, Popescu G, Cheng JX. Bond-selective transient phase imaging via sensing of the infrared photothermal effect. LIGHT, SCIENCE & APPLICATIONS 2019; 8:116. [PMID: 31839936 PMCID: PMC6904725 DOI: 10.1038/s41377-019-0224-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 11/07/2019] [Accepted: 11/18/2019] [Indexed: 05/06/2023]
Abstract
Phase-contrast microscopy converts the phase shift of light passing through a transparent specimen, e.g., a biological cell, into brightness variations in an image. This ability to observe structures without destructive fixation or staining has been widely utilized for applications in materials and life sciences. Despite these advantages, phase-contrast microscopy lacks the ability to reveal molecular information. To address this gap, we developed a bond-selective transient phase (BSTP) imaging technique that excites molecular vibrations by infrared light, resulting in a transient change in phase shift that can be detected by a diffraction phase microscope. By developing a time-gated pump-probe camera system, we demonstrate BSTP imaging of live cells at a 50 Hz frame rate with high spectral fidelity, sub-microsecond temporal resolution, and sub-micron spatial resolution. Our approach paves a new way for spectroscopic imaging investigation in biology and materials science.
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Affiliation(s)
- Delong Zhang
- Department of Biomedical Engineering, Boston University, Boston, MA 02215 USA
- Department of Physics, Zhejiang University, Hangzhou, 310028 China
| | - Lu Lan
- Department of Biomedical Engineering, Boston University, Boston, MA 02215 USA
| | - Yeran Bai
- Department of Biomedical Engineering, Boston University, Boston, MA 02215 USA
- National Laboratory on High Power Laser and Physics, Shanghai, 201800 China
- Key Laboratory of High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800 China
| | - Hassaan Majeed
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Champaign, IL 61801 USA
| | - Mikhail E. Kandel
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Champaign, IL 61801 USA
| | - Gabriel Popescu
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Champaign, IL 61801 USA
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Champaign, IL 61801 USA
| | - Ji-Xin Cheng
- Department of Biomedical Engineering, Boston University, Boston, MA 02215 USA
- Department of Electrical & Computer Engineering, Boston University, Boston, MA 02215 USA
- Photonics Center, Boston University, Boston, MA 02215 USA
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Ling T, Boyle KC, Goetz G, Zhou P, Quan Y, Alfonso FS, Huang TW, Palanker D. Full-field interferometric imaging of propagating action potentials. LIGHT, SCIENCE & APPLICATIONS 2018; 7:107. [PMID: 30564313 PMCID: PMC6290013 DOI: 10.1038/s41377-018-0107-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 11/24/2018] [Accepted: 11/24/2018] [Indexed: 05/15/2023]
Abstract
Currently, cellular action potentials are detected using either electrical recordings or exogenous fluorescent probes that sense the calcium concentration or transmembrane voltage. Ca imaging has a low temporal resolution, while voltage indicators are vulnerable to phototoxicity, photobleaching, and heating. Here, we report full-field interferometric imaging of individual action potentials by detecting movement across the entire cell membrane. Using spike-triggered averaging of movies synchronized with electrical recordings, we demonstrate deformations up to 3 nm (0.9 mrad) during the action potential in spiking HEK-293 cells, with a rise time of 4 ms. The time course of the optically recorded spikes matches the electrical waveforms. Since the shot noise limit of the camera (~2 mrad/pix) precludes detection of the action potential in a single frame, for all-optical spike detection, images are acquired at 50 kHz, and 50 frames are binned into 1 ms steps to achieve a sensitivity of 0.3 mrad in a single pixel. Using a self-reinforcing sensitivity enhancement algorithm based on iteratively expanding the region of interest for spatial averaging, individual spikes can be detected by matching the previously extracted template of the action potential with the optical recording. This allows all-optical full-field imaging of the propagating action potentials without exogeneous labels or electrodes.
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Affiliation(s)
- Tong Ling
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 USA
- Department of Ophthalmology, Stanford University, Stanford, CA 94305 USA
| | - Kevin C. Boyle
- Department of Electrical Engineering, Stanford University, Stanford, CA 94305 USA
| | - Georges Goetz
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 USA
| | - Peng Zhou
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305 USA
| | - Yi Quan
- Department of Ophthalmology, Stanford University, Stanford, CA 94305 USA
| | - Felix S. Alfonso
- Department of Chemistry, Stanford University, Stanford, CA 94305 USA
| | - Tiffany W. Huang
- Department of Electrical Engineering, Stanford University, Stanford, CA 94305 USA
| | - Daniel Palanker
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 USA
- Department of Ophthalmology, Stanford University, Stanford, CA 94305 USA
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