Bond-selective intensity diffraction tomography

Abstract

Recovering molecular information remains a grand challenge in the widely used holographic and computational imaging technologies. To address this challenge, we developed a computational mid-infrared photothermal microscope, termed Bond-selective Intensity Diffraction Tomography (BS-IDT). Based on a low-cost brightfield microscope with an add-on pulsed light source, BS-IDT recovers both infrared spectra and bond-selective 3D refractive index maps from intensity-only measurements. High-fidelity infrared fingerprint spectra extraction is validated. Volumetric chemical imaging of biological cells is demonstrated at a speed of ~20 seconds per volume, with a lateral and axial resolution of ~350 nm and ~1.1 µm, respectively. BS-IDT's application potential is investigated by chemically quantifying lipids stored in cancer cells and volumetric chemical imaging on Caenorhabditis elegans with a large field of view (~100 µm x 100 µm).

Mid-Infrared Photothermal Microscopy: Principle, Instrumentation, and Applications

“…Since the first report of high-performance chemical imaging of living cells and organisms at submicron resolution, MIP microscopy has evolved in various ways. On the detection side, various methods including interferometric scattering, , optical phase, − lock-in phase, PA detection, , fluorescence detection, − signal digitization, and computational tomography , significantly improved the performance and broadened the application field. Meanwhile, advances are made in pushing the imaging resolution, speed, and sensitivity of MIP to the next stage.…”

“…The Lihong Wang group pushed the MIP spatial resolution to 260 nm by employing ultraviolet-excited PA detection of MIP signals . The Ideguchi and Cheng groups realized depth-resolved MIP imaging of biological samples using optical diffraction tomography (ODT) and intensity diffraction tomography (IDT), respectively. The Cheng and Simpson groups had two back-to-back JACS publications showing the mid-IR modulation of fluorescence, which not only increases the specificity of MIP but also provides a 100-fold enhancement in modulation depth compared to the modulation of scattering intensity.…”

“…More recently, the Cheng and Tian groups reported a bond-selective intensity diffraction tomography (BS-IDT) scheme for a noninterferometric volumetric MIP imaging of cells and organisms . A customized nanosecond pulsed laser ring array is integrated with the time-gated pump pulses in BS-IDT, which enables the acquisition of transient 3D refractive index variations at microsecond time scale.…”