Recently, the Probe and Chemical Biology Team of the School of Chemistry and Chemical Engineeringof Guangxi Univeristyhas made a breakthrough in NIR-II(900-1700 nm)opticalimaging.The team constructed a series of activatable NIR-II photoacoustic dyes platform GX, publishing a papertitled“A Class of Activatable NIR-II Photoacoustic Dyes for High-Contrast Bioimaging”(DOI: 10.1002/anie.202312632)inAngewandte Chemie International Edition, which focuses onthe challenge thatthe lack of groupsthat facilitate theoptical tuning in NIR-II photoacoustic dyes hinders the effective applicationofNIR-II photoacoustic dyesin complex and diverse molecular imaging.Theleadauthor of the paper is LiJiangfeng, a Ph.D.candidateof the School of Chemistry and Chemical Engineeringin Guangxi University, and the corresponding author is Prof.Dr.LinWeiying,Guangxi Universitybeingthe firstaffiliation.

Photoacoustic (PA)Imaging is becoming one of the important non-invasive imaging techniques in biomedical research. However, most of the current conventional photoacoustic dyes have wavelengths concentrated in the visible and NIR-I(700-900 nm), which have limited tissue penetration depth and spatial resolution. In contrast, photoacoustic dyes in NIR-II can provide more comprehensive and in-depth in vivo physiological and pathological information. Due tothe lack of groupsthat facilitate theoptical tuning, NIR-II photoacoustic dyes typically exhibita“always-on”feature, which hinders their effective use in complex and diverse molecular imaging applications.

Inorder tosolve the uncontrolled“on-off” photoacoustic signals, the team designed a novel rhodamine-based NIR-II photoacoustic dye platform GX, with the same powerful optical switching mechanism as that of traditional rhodamine dyesandthe absorption and emission wavelengths of NIR-II,the absorptionandemission wavelengths of the dye GX-5 reaching up to 1082nm and1360 nmrespectively.TheDFTcalculations have shown that the GX dye possesses the structural features typical of rhodamine dyes, with smallermolecularorbital gaps and larger dipole moments, compared to the conventional rhodamine dyes in the visible region and the NIR-Iofrhodamine dyes. To further demonstrate the excellent photoacoustic properties of dye GX, theleadauthor used dye GX-5 to visualize the distribution and structure of the mouse vascular system in 3D by photoacoustic imaging. In addition, using dye GX-5 as an activatable dye platform, the authors further constructed the first NIR-II probe GX-5-CO for the specific detection of carbon monoxide, whichisable to reveal enhanced carbon monoxide levels in hypertensive mice by high-contrast NIR-II photoacoustic imaging, demonstrating the value of the novel NIR-II functional rhodamine-based photoacoustic dye GX. This work will not only inspire researchers to develop efficient small-molecule NIR-II dye platforms for target-activatable photoacoustic probes, but will also promote further application of NIR-II dyes in photoacoustic imaging for precise imagingtoguide diseaseswithcomplexdiagnoses and surgeries.

It isknownthat the Probe and Chemical Biology team relies on the School of Chemistry and Chemical Engineering and the Institute of Optical Functional Materials and Chemical Biology of Guangxi University.The head of the team, Prof.Dr. LinWeiying, Fellow of the Royal Society of Chemistry,serves as the Editor ofSensors and Actuators B: Chemical. As a corresponding author, Prof.Dr.LinWeiying has published more than 450qualitypapers, includingNature Protocols,Chemical Reviews,Journal of the American Chemical Society,Angewandte Chemie International Edition, etc., whosepapers have been cited more than 24,900 times.

(Prof.Dr. Lin Weiying’s Research Team)