Long‐Lived Second Near‐Infrared Luminescent Probes: An Emerging Role in Time‐Resolved Luminescence Bioimaging and Biosensing

Abstract

Luminescence bioimaging and biosensing in the second near‐infrared (NIR‐II) spectral window (1,000–1,700 nm wavelengths) is a newly emerging technique that is extensively used in fundamental research and clinical practice. Owing to its advantages, including deep tissue penetration and excellent temporal resolution, this technique has shown tremendous promise for target‐specific imaging and noninvasive monitoring. However, developing bioimaging modalities that enable target‐specific imaging with high resolution and sensitivity remains a great challenge today. Compared with NIR‐II fluorescence imaging, NIR‐II luminescence lifetime imaging with advantages such as lower background noises, higher sensitivity, and higher spatial resolution has opened up new avenues for deep tissue imaging and biomedical applications. Herein, various types of long‐lived NIR‐II luminescent probes, including complex dyes, rare‐earth‐doped nanoparticles, organic compound‐loaded nanoparticles, inorganic‐based dots and nanotubes, as well as the main types of time‐resolved luminescence techniques including time‐domain (e.g., time‐correlated single‐photon counting, time‐gated detection, pulse sampling, etc.) and frequency‐domain systems are first summarized. The unique advantages of long‐lived NIR‐II luminescent probes and their critical roles in bioimaging and biosensing are also highlighted. Finally, the present challenges and future directions of long‐lived NIR‐II luminescent probes in biomedical research, translational research, and (pre‐)clinical studies are discussed.

Preparation of rare earth-doped nano-fluorescent materials in the second near-infrared region and their application in biological imaging

“…In order to meet this challenge, researchers have turned their research direction to the time domain. 6,177,178 In recent years, researchers have designed many nano-fluorescent probes with long life. 179 The core-multishell nanostructure is an effective method to realize the long-life imaging of nanoparticles.…”

Molecularly Engineered Room-Temperature Phosphorescence for Biomedical Application: From the Visible toward Second Near-Infrared Window

“…In this context, the guideline for developing optical probes with room-temperature phosphorescence can be carefully revised to "the longer the wavelength and lifetime, the better the bioimaging performance". As one promising research direction, long-wavelength and long-lived phosphorescence will be investigated intensively, 395 and is sure to shine in the optical imaging community.…”

Brightness Strategies toward NIR-II Emissive Conjugated Materials: Molecular Design, Application, and Future Prospects

“…However, the development of NIR-II fluorescence bioimaging is in its infancy, and many fluorescent probes have relatively weak absorption and emission in the NIR-II window, resulting in poor imaging performance . To achieve high-performance NIR-II bioimaging, various materials with bright NIR-II emission have been extensively explored in the past few years and can be divided into two main categories: inorganic materials − and organic materials. − Since the pioneering research on the use of single-walled carbon nanotubes for in vivo NIR-II fluorescence imaging, an increasing number of inorganic NIR-II fluorescence materials, including rare earth nanoparticles, − inorganic quantum dots, − and gold nanoclusters, − have been extensively used in NIR-II fluorescence biological imaging. Inorganic materials have relatively high quantum yields and low photobleaching sensitivity; however, practical clinical applications of these materials are still limited owing to concerns about biosafety and biocompatibility.…”