Evolving a novel red-emitting two-photon dye with optically tunable amino group for monitoring the degree of hypoxia during liver fibrosis

Two-photon imaging has attracted increasing attention owing to its deep tissue imaging capabilities. Therefore, many fluorophores have been developed to satisfy its requirements. However, long-wavelength emission fluorophores with an optically tunable group are rarely developed. In this study, two long -wavelength emission fluorophores with an optically tunable amino group were successfully developed by introducing strong electron acceptor and large conjugated group to the TPQL dye. TPCO2 displayed a bright red emission (lambda em = 638 nm, 0 = 0.15) together with high two-photon action cross section and good water solubility, which enabled higher signal-to-background ratios and deep tissue imaging. The proof-of-concept probe (TPCO -NO2) was successfully applied to the high signal-to-background ratio imag-ing of nitroreductase in liver fibrosis, further realizing diagnosis of the degree of hypoxia during liver fibrosis. (c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.