Optical Imaging in the Second Near Infrared Window for Vascular Bioimaging

Abstract

Optical imaging in the second near infrared region (NIR‐II, 1000–1700 nm) provides higher resolution and deeper penetration depth for accurate and real‐time vascular anatomy, blood dynamics, and function information, effectively contributing to the early diagnosis and curative effect assessment of vascular anomalies. Currently, NIR‐II optical imaging demonstrates encouraging results including long‐term monitoring of vascular injury and regeneration, real‐time feedback of blood perfusion, tracking of lymphatic metastases, and imaging‐guided surgery. This review summarizes the latest progresses of NIR‐II optical imaging for angiography including fluorescence imaging, photoacoustic (PA) imaging, and optical coherence tomography (OCT). The development of current NIR‐II fluorescence, PA, and OCT probes (i.e., single‐walled carbon nanotubes, quantum dots, rare earth doped nanoparticles, noble metal‐based nanostructures, organic dye‐based probes, and semiconductor polymer nanoparticles), highlighting probe optimization regarding high brightness, longwave emission, and biocompatibility through chemical modification or nanotechnology, is first introduced. The application of NIR‐II probes in angiography based on the classification of peripheral vascular, cerebrovascular, tumor vessel, and cardiovascular, is then reviewed. Major challenges and opportunities in the NIR‐II optical imaging for vascular imaging are finally discussed.

Semiconductor Polymer with Strong NIR-II Absorption for Photoacoustic Imaging and Photothermal Therapy

“…The detailed synthetic route is shown in Scheme S1. We first synthesized a building block of 4,9-dibromo-6,7-diphenyl- [1,2,5] thiadiazolo [3,4-g] quinoxaline bearing two PEG chains and then performed the Suzuki reaction with 2,5-bisthiopheneboronic acid pinacol ester under the catalysis of palladium(II) acetate, producing the semiconductor polymer PTPTQ. PTPTQ is soluble in water and various organic solvents, e.g., tetrahydrofuran, toluene, and dichloromethane.…”

“…Noninvasive biological imaging is widely used in studies of physiological and pathological processes in clinical and scientific research . Among the various imaging techniques, photoacoustic (PA) imaging is very promising because of its high imaging depth, good spatial resolution, and easy-to-get contrast agents. − In PA imaging, the contrast agents are excited by pulsed laser, undergo photothermal conversion, and further produce acoustic waves .…”

Biomedical Photoacoustic Imaging for Molecular Detection and Disease Diagnosis: “Always‐On” and “Turn‐On” Probes

“…[110] Whether using endogenous or exogenous contrast agents, PA imaging must depend on the contrast agents' photothermal conversion to create mechanical waves in order to detect the acoustic signal, which may not give sufficient information for weak light-absorbing tissue. Additionally, although PA imaging can acquire vascular images, it can only produce fuzzy deep vascular images or vivid epidermal vascular images, [202][203][204][205][206] which are not comparable to ultrasound, CT, MRI, or digital subtraction angiography.…”

The Advances and Biomedical Applications of Imageable Nanomaterials

“…Since optical imaging could directly monitor the molecular level to track the dynamic process of metabolism in vivo , it has been widely used in various biological studies. Therefore, giving nanomaterials to optical and other imaging properties realized the dynamic monitoring of molecules and overcame the shortcomings of optical imaging that are limited by the depth of the tissue ( Wang Z. a. et al, 2021 ; Ding et al, 2021 ; Luo et al, 2021 ; Xu et al, 2021 ). Coating or mounting near-infrared fluorescent pigments, targeting markers, and radioactive elements on nanomaterials could achieve PET/near-infrared dual-modal imaging of tumor-associated macrophages in mouse ( Kwon et al, 2021 ).…”