Lei Zuhai's research group has made progress in the ratiometrically responsive near-infrared two-region fluorescence molecular imaging platform

The Lei Zuhai research group of the School of Pharmacy of Fudan University has made progress
in the field of near-infrared zone II (NIR-II) fluorescence imaging.
The research project designed and constructed a NIR-II ratiometric fluorescent probe molecular platform, which can realize the quantitative visual monitoring of biomolecules such as enzymes in living deep tissues, and the relevant results are entitled "Polymethine Molecular Platform for Ratiometric Fluorescent Probes in the Second near-Infrared Window".
Published as a newsletter in the Journal of the American Chemical Society
.

Fluorescence imaging in the second region of near infrared (NIR-II) has the advantages of deep penetration depth and weak light scattering, and has been widely used in fluorescence imaging
of deep tissues in vivo.
At present, the fluorescent probes in the NIR-II region are mainly "off-on" probes, which can be selectively activated by specific substrates in vivo to give signals, but they can only achieve "have" and "no" signal changes, and the use of "off-on" fluorescent probes can achieve qualitative visual monitoring of specific substrates in the tumor microenvironment such as enzymes and ROS/RNS, but can not achieve quantitative change monitoring
.
In contrast, ratiometric fluorescent probes can acquire signals through multiple channels and correlate the signals of each channel, which has a self-correction function and can realize quantitative analysis and monitoring
.
However, up to now, the ratio fluorescent probes and probe design strategies in the NIR-II region are relatively small, and the bottom species that can be detected are mainly strong oxidizing substances, which cannot meet the detection needs
of enzymes and other biomolecules.

Recently, young researchers of Lei Zuhai combined the Rhodamine 6G molecular skeleton and polymethylyne to design and develop a molecular platform Py-2 with an emission spectrum in the near-infrared second region, based on which a series of ratiometric fluorescent probes
can be constructed.
The study found that after the amino acetylation on the Py-2 molecule, its absorption spectrum was blue-shifted, but it still maintained the fluorescence emission
in the near-infrared region 2.
Therefore, a ratiometric sensing probe
can be constructed by adjusting the intramolecular charge transfer (ICT) properties of amino groups.
To verify the universality of the platform molecules, ratiometric fluorescent probes Rap-N and Rap-R in response to nitroreductase and ROS/RNS, respectively, were synthesized, and both probes showed good ratiometric fluorescence responses
for specific substrates.
In vivo experiments, Rap-N realized semi-quantitative monitoring of nitroreductase of different tumors, and Rap-R realized real-time monitoring
of liver injury and peritonitis.

Probe response mechanism and its application in tumor hypoxic imaging

In this work, a molecular platform Py-2 with emission in the NIR region was designed, which has good universality, based on which two ratiometric molecular fluorescent probes were constructed and the visualization and quantitative monitoring
of biomolecules such as enzymes and ROS/RNS in living deep tissues was realized.
As a platform molecule, Py-2 can be easily developed into a NIR-II ratiometric molecular fluorescent probe for various detection purposes
.

The first author of the paper is Lan Qingchun, a postdoctoral fellow at Fudan University, and Yu Peng, a doctoral student, and the corresponding author is Lei Zuhai, a young researcher
.
This work is strongly supported
by the School of Pharmacy of Fudan University, the Key Laboratory of Intelligent Drug Delivery of the Ministry of Education, as well as the National Natural Science Foundation of China, the Shanghai Municipal Science and Technology Commission, and the start-up funds of Fudan University.

Original link: https://pubs.
acs.
org/doi/full/10.
1021/jacs.
2c10041