Optical and Photoacoustic Imaging In Vivo: Opportunities and Challenges

Abstract

Optical and photoacoustic imaging plays an important role in biomedical applications owing to its noninvasiveness and high resolution. Fluorescence imaging and photoacoustic imaging emerge as powerful tools to deconstruct molecular information and investigate biological processes in vivo. Despite great progress has been achieved in chemical probe synthesis, how to design probes with optimal fluorescence or photoacoustic imaging performance to dynamically visualize the biological process in vivo still faces challenges. From this perspective, we will focus on the advanced development of fluorescence and photoacoustic imaging in vivo. Furthermore, concerns and prospects for future imaging in vivo will be demonstrated.

Recent Advances in Activatable Probes for Molecular Imaging by Stimuli‐Controlled Disassembly

“…Comparatively, the second near‐infrared window (NIR‐II, 1000—1700 nm) showed improved tissue penetration, as the photon scattering and autofluorescence were reduced, allowing for higher imaging SNR and spatial resolution. [ 77–80 ] Despite these superior merits, the activatable molecular NIR‐II probes are still full of challenges due to the lack of efficient strategy to switch on the NIR‐II FLI and PAI signals. For example, the NIR‐II fluorophores generally required molecular structures with elongated π‐conjugation, in which the ICT effect was not as efficient as that in the NIR‐I fluorophores.…”

A Near-infrared Fluorescence and Positron Emission Tomography Bimodal Probe for In Vivo Imaging of Amyloid-β Species

“…Over the past few decades, many Aβ species-targeting molecular imaging probes, including fluorescence (FL) probes, − PET probes, − and magnetic resonance imaging (MRI) probes, − have been developed for in vivo visualization of the Aβ species. Particularly, multimodal imaging probes that combine different imaging modalities to produce complementary information on Aβ species in the brain have shown advantages over mono-imaging probes. − For example, several bimodal probes combining FL imaging and MRI have been reported, aiming to offer high sensitivity and high spatial resolution for the imaging of Aβ species. − In addition, a few bimodal probes combining FL imaging with PET or single-photon emission computed tomography (SPECT) have been developed for the imaging of Aβ species as well. ,− However, the fluorescence of these bimodal probes fell out of the NIR range (λ em < 650 nm) after binding to the Aβ species, which displayed shallow penetration depth and were not efficient to noninvasively detect the Aβ species in the brain. What is more, these bimodal probes were reported to respond to insoluble Aβ plaques only, not to the soluble Aβ monomers and oligomers, which may preclude the ability for the early diagnosis of AD.…”

Luciferase-Decorated Gold Nanorods as Dual-Modal Contrast Agents for Tumor-Targeted High-Performance Bioluminescence/Photoacoustic Imaging

“…4−6 In recent times, research on nanoparticles with optical and photoacoustic (PA) imaging ability has attracted escalating interest in biomedical applications owing to their noninvasiveness, high resolution, and timeliness. 3 Conse-quently, the development of various nanoprobes has opened up new avenues for cancer diagnosis and treatment. 7−9 Toward this goal, gold nanorods (AuNRs) have been considered highly compelling materials for their highly efficient absorption in the NIR regions to penetrate biological tissues with relatively high transmissivity.…”

“…Conventional imaging modalities such as X-ray computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) are costly, require rigorous clinical practice radioactive contrast agents, and ultimately impose a psychological burden on patients . Despite the breadth of analytical tools available for cancer diagnosis, multimodal molecular imaging has been considered as one of the most effective imaging techniques for real-time reflection of dynamic biological status and visualization of tumors. − In recent times, research on nanoparticles with optical and photoacoustic (PA) imaging ability has attracted escalating interest in biomedical applications owing to their noninvasiveness, high resolution, and timeliness . Consequently, the development of various nanoprobes has opened up new avenues for cancer diagnosis and treatment. − Toward this goal, gold nanorods (AuNRs) have been considered highly compelling materials for their highly efficient absorption in the NIR regions to penetrate biological tissues with relatively high transmissivity. − Utilizing the fantastic optical characteristic properties of AuNRs, Chu and co-workers developed lactose-functionalized AuNRs as efficient biosensors for the detection of a galectin-1 cancer biomarker based on the high specificity of lactose toward galectin-1 .…”