Near-infrared (NIR) fluorescence imaging has been proved as an effective modality in identifying the tumor border and distinguishing the tumor cells from healthy tissue during the oncological surgery. Developing NIR fluorescent probes with high tumor to background (T/B) signal is essential for the complete debulking of the tumor, which will prolong the survival rate of tumor patients. However, the nonspecific binding and “always-on” properties of the conventional fluorescent probes leads to high background signals and poor specificity.

Peroxynitrite (ONOO⁻) is a crucial reactive oxygen species that plays a vital role in cellular signal transduction and homeostatic regulation. Determining and visualizing peroxynitrite accurately in biological systems is important for understanding its roles in physiological and pathological activity. Among the various detection methods, fluorescent probe-based spectroscopic detection offers real-time and minimally invasive detection, high sensitivity and selectivity, and easy structural and property modification. This review categorizes fluorescent probes by their fluorophore structures, highlighting their chemical structures, recognition mechanisms, and response behaviors in detail. We hope that this review could help trigger novel ideas for potential medical diagnostic applications of peroxynitrite-related molecular diseases.

Background: Abnormal Cu(II) ions levels may affect many biological functions, and it is of great importance to detect Cu(II) ions in organisms. Methods: Herein, we report a near-infrared (NIR) fluorescent probe EtRh-N-NH𝟐 for the detection of Cu(II). In the probe structure, a rhodamine core was used, and a hydrazine group was employed as the responsive site. Results & Conlusions: EtRh-N-NH𝟐 displayed sensitive, specific and fast response upon Cu(II) with excellent linear relationship between the concentration and fluorescence emission intensity in 0–1 μM range. The releasing EtRh-COOH exhibited 762 nm of emission wavelength with a 75 nm of Stokes shift.