Fluorescence imaging in near-infrared IIb (NIR-IIb, 1500–1700 nm) spectrum holds a great promise for tissue imaging. While few inorganic NIR-IIb fluorescent probes have been reported, their organic counterparts are still rarely developed, possibly due to the shortage of efficient materials with long emission wavelength. Herein, we propose a molecular design philosophy to explore pure organic NIR-IIb fluorophores by manipulation of the effects of twisted intramolecular charge transfer and aggregation-induced emission at the molecular and morphological levels. An organic fluorescent dye emitting up to 1600 nm with a quantum yield of 11.5% in the NIR-II region is developed. NIR-IIb fluorescence imaging of blood vessels and deeply-located intestinal tract of live mice based on organic dyes is achieved with high clarity and enhanced signal-to-background ratio. We hope this study will inspire further development on the evolution of pure organic NIR-IIb dyes for bio-imaging.

The first water-soluble NIR AIEgen was synthesized and used for ultrafast wash-free cellular imaging and photodynamic cancer cell ablation.

Light has profoundly impacted modern medicine and healthcare, with numerous luminescent agents and imaging techniques currently being used to assess health and treat diseases. As an emerging concept in luminescence, aggregation-induced emission (AIE) has shown great potential in biological applications due to its advantages in terms of brightness, biocompatibility, photostability, and positive correlation with concentration. This review provides a comprehensive summary of AIE luminogens applied in imaging of biological structure and dynamic physiological processes, disease diagnosis and treatment, and detection and monitoring of specific analytes, followed by representative works. Discussions on critical issues and perspectives on future directions are also included. This review aims to stimulate the interest of researchers from different fields, including chemistry, biology, materials science, medicine, etc., thus promoting the development of AIE in the fields of life and health.

The emergence of the aggregation-induced emission (AIE) concept significantly changes the cognition of scientific community toward classic photophysical phenomenon. More importantly, the AIE phenomenon has brought huge opportunities for the analysis of bioactive species, monitoring of complicated biological processes, and elucidation of key physiological/pathological behaviors. As a class of promising luminescent materials, AIE luminogens (AIEgens) are weakly or non-emissive in the form of isolated molecular species, but emit particularly strong fluorescence in the aggregated and/or solid states. Motivated by the prominent advantages such as high brightness, large Stokes shift, excellent photostability, and good biocompatibility, AIEgen-based bioprobes have been widely explored in the field of biomedicine. This review aims to provide a systematic summary on the developmental history and an in-depth perspective on the current landscape of AIE in the biomedical field, with an emphasis on the discussions of major working principles. The milestones of the historical development of AIE in the biomedical field are first reviewed. Four major research directions are then extracted, including biomacromolecule sensing (at the molecular level), in vitro cell imaging (at the cellular level), in vivo imaging (at the animal level), and cancer theranostics (at the cellular and animal levels), together with clear-cut tables showing comprehensive cases for further study. Lastly, this review is concluded by the discussions of several perspectives on future directions. It is believed that AIEgen-based bioprobes will play vital roles in the exploration of mysterious life processes by integration with various cutting-edge modalities/techniques, with an ultimate goal to address more healthcare issues.