Rational design of a nitroreductase-activatable two-photon fluorescent probe for hypoxia imaging in cell and in vivo

• We developed a two-photon fluorescent probe, TP-NO 2 , with simple synthesis steps and high yield. • TP-NO 2 could determination of nitroreductase in a wide range (0−20 μg/mL) with a low detection limit of 26 ng/mL. • TP-NO 2 could be applied for nitroreductase detection in hypoxia cells and tumor-bearing mice models. • TP-NO 2 is a promising tool for clinical surgery pre-evaluation during tumor treatment via nitroreductase detection. Tumor resistance is a huge challenge for tumor treatment, which may lead to tumor treatment failure. Relieving tumor resistance and improving efficacy are long-term goals for tumor treatment. Nitroreductase (NTR) is an endogenous enzyme that highly expressed in hypoxia tumors. Herein, we develop a NTR-activatable fluorescent probe, TP-NO 2 , for NTR detection during tumor treatment. TP-NO 2 with simple synthesis steps and high yield can qualitatively and quantitatively detect NTR in a wide range (0−20 μg/mL) with a detection limit of 26 ng/mL. The probe has been successfully applied for NTR detection in cells under simulated hypoxia conditions. Hyperbaric oxygen (HBO) can alleviate tumor hypoxia and reduce NTR concentration. We pre-evaluate the effect of tumor treatment by NTR imaging. And the results demonstrate that HBO-assistant chemotherapy can effectively treat tumor cells. We further apply TP-NO 2 for NTR detection in A549 and cis -dichlorodiamineplatinum(II) (DDP)-resistant A549 (A549/DDP) xenograft nude mice, and we choose NTR as an indicator to pre-evaluate the treatment efficacy of malignant tumors. With the adjuvant therapy of HBO, chemotherapeutic drugs gemcitabine and carboplatin can effectively treat A549 and A549/DDP xenograft. These applications provide us a novel perspective for NTR imaging.