Three‐dimensional cellular imaging in thick biological tissue with confocal detection of one‐photon fluorescence in the near‐infrared II window

Abstract

Fluorescence imaging in the second near‐infrared optical window (NIR‐II, 900‐1700 nm) has become a technique of choice for noninvasive in vivo imaging in recent years. Greater penetration depths with high spatial resolution and low background can be achieved with this NIR‐II window, owing to low autofluorescence within this optical range and reduced scattering of long wavelength photons. Here, we present a novel design of confocal laser scanning microscope tailored for imaging in the NIR‐II window. We showcase the outstanding penetration depth of our confocal setup with a series of imaging experiments. HeLa cells labeled with PbS quantum dots with a peak emission wavelength of 1276 nm can be visualized through a 3.5‐mm‐thick layer of scattering medium, which is a 0.8% Lipofundin solution. A commercially available organic dye IR‐1061 (emission peak at 1132 nm), in its native form, is used for the first time, as a NIR‐II fluorescence label in cellular imaging. Our confocal setup is capable of capturing optically sectioned images of IR‐1061 labeled chondrocytes in fixed animal cartilage at a depth up to 800 μm, with a superb spatial resolution of around 2 μm.

Ultra-low-cost and high-fidelity NIR-II confocal laser scanning microscope with Bessel beam excitation and SiPM detection

“…Advantageous imaging effects have been reported in the NIR-II band, such as widefield microscope [11][12][13][14], light sheet microscope [15][16][17], CLSM [18][19][20][21], two-photon and multiphoton microscope [22][23][24][25].…”

Ultra-low-cost and high-fidelity NIR-II confocal laser scanning microscope with Bessel beam excitation and SiPM detection

“…Advantageous imaging effects have been reported in the NIR-II band, such as widefield microscope [11][12][13][14], light sheet microscope [15][16][17], CLSM [18][19][20][21], two-photon and multiphoton microscope [22][23][24][25].…”

Multifunctional Nanoplatform for NIR-II Imaging-Guided Synergistic Oncotherapy

“…NIR-II light (wavelength 1000-1700 nm), with its longer wavelength and weaker interaction with biological tissues can be a good solution to this problem. In addition, recent studies have shown that compared with NIR-I light, NIR-II light has lower photon dispersion, less tissue absorption, higher sensitivity, relatively higher maximum permissible skin exposure (MPE), more optimal tissue penetration depth (up to 3.5 mm), and better spatial resolution during laser irradiation [21,22]. Therefore NIR-II-responsive tumor imaging has more important applications in biological and medical fields.…”