Polymethine fluorophores for in vivo shortwave infrared imaging
Fluorescence imaging is a central tool for visualizing complex biological systems, yet the contrast and resolution attainable in vivo is limited by diffuse light originating from background and scattering at visible and near-infrared (NIR) wavelengths. Recently, the shortwave infrared region of the electromagnetic spectrum (SWIR, 1000 – 2000 nm) has emerged as an optimal region for in vivo fluorescence imaging due to its minimal light scattering and low tissue autofluorescence compared to the NIR. While the SWIR demonstrates great promise, suitable materials are needed with emission at these low energies for the development of optical contrast agents. Namely, non-toxic organic small molecules with bright emission > 1000 nm are necessary to expand both the basic science and clinical applications of fluorescence imaging.
Our group develops biocompatible polymethine fluorophores for the shortwave infrared region. In 2017, we discovered a bright shortwave infrared emitter containing flavylium heterocycles that we deemed Flav7. Since that time, we have systematically investigated Flav7 using physical organic chemistry approaches and can now predictably tune the absorption and emission properties. These insights have lead to new SWIR fluorophores that enable multiplexed real time in vivo imaging and the fastest SWIR imaging to date.