A novel internal standard ratio fluorescent probe for nitroreductase detection in cells

Abstract

Hypoxia is a significant feature of tumor tissue, which is of great significance in assessing the malignancy of tumors. Nitroreductase (NTR) is an enzyme that is highly expressed in hypoxic cells, and its activity can be used to judge the degree of hypoxia in cells. In this work, we developed a novel internal standard ratio-type fluorescent probe CS–CN–NO, which has two emission signals, namely the NTR-sensitive response signal at 530 nm (I₅₃₀) and the almost invariable reference signal at 700 nm (I₇₀₀). Similar to the internal standard method, this unique signal feature enables the probe to accurately detect NTR in cells, reducing the error caused by the complex physiological environment in the cell. The probe has fast response time (16 min), low detection limit (70 ng mL⁻¹) and good biocompatibility. Cell imaging studies show that the probe has the ability to detect NTR in hypoxic cells, and can directly show the degree of hypoxia in cells.