NIR skull optical clearing window for in vivo cortical vasculature imaging and targeted manipulation
Dong-yu LI1,2,3, Zheng ZHENG4, Ting-Ting YU1,3, Ben Zhong TANG4, Peng FEI5, Jun QIAN2 and Dan ZHU1,3
1 Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, China
2 State Key Laboratory of Modern Optical Instrumentation, Centre for Optical and Electromagnetic Research, College of Optical Science and Engineering, Zhejiang University, China
3 MoE Key Laboratory for Biomedical Photonics, Huazhong University of Science and Technology, China
4 Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction Division of Life Science, State Key Laboratory of Molecular Neuroscience, Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, The Hong Kong University of Science and Technology, China
5 School of Optical and Electronic Information-Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, China
Abstract
In vivo observation of brain in its natural environment is of vital significance to better understand the function of vasculature and neural networks, as well as various diseases related to the dysfunction of brain. Modern optical imaging technology combined with a variety of fluorescent labelling technology can obtain the structure and function information of biological tissue with high spatial and temporal resolution, providing an important means for brain science. However, the high scattering characteristic of skull limits the penetration depth of light. Since the scattering of tissue decreases with the increase of wavelength, the imaging in near infrared band, especially in the second region of near infrared, shows great advantages for improving the ability of optical imaging in deep tissue imaging. Compared to two-photon fluorescence or second harmonic generation, three-photon fluorescence or third harmonic generation (THG) based on longer wavelength excitation, can obtain deeper information with high resolution.
The recent development of tissue optical clearing technology reduces the effect of scattering from another perspective, providing a new idea for deep tissue imaging. With the novel skull optical clearing window, optical imaging techniques, laser speckle contrast imaging, hyperspectral imaging and two-photon fluorescence microscopy have been applied to observe cortical neuron, microglia, vascular structures and functions.
Since NIR-II excitation based nonlinear optical microscopy and skull optical clearing are useful means, respectively, to realize in vivo cortical imaging without craniotomy, does the combination of the both have an enhancement effect? After all, the previous optical clearing windows only demonstrated the efficacy of optical imaging in the wavelength range of visible to NIR-I.
In this work, we systematically studied the combination of NIR-II excited THG microscopy and in vivo tissue optical clearing technique, and further developed Vis-NIR-II compatible optical clearing skull window. Compared with the previous urea-based skull optical clearing agent (USOCA), the newly developed vis-NIR-II optical clearing agent (VNSOCA) not only had the same transmittance in the shorter wavelength range, but also had greatly enhanced transmittance in the near infrared region.
The optical clearing window could remarkably increase signal intensity as well as the imaging depth of cortical THG vascular imaging. Finally, the imaging depth of 650 μm was obtained, which was even close to it without skull.
In addition of imaging, the effectiveness of optical manipulation is also significant. The results showed that precise NIR-II light manipulation could be performed through the established skull optical clearing window. Using the 1550-nm fs laser, both large vessel or small capillary could be targeted injured.
The novel Vis-NIR-II optical clearing skull window is well adapted to the whole band from visible light to NIR-II region, which greatly expands the wavelength selection range of deep cortex optical imaging and can effectively combine various NIR-II imaging technologies developed in recent years. The first established scalp-cranial window model further simplifies the cranial window model and provides a new approach for imaging the transcranial cortex in vivo.
Speaker
Dongyu Li
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology
China
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