Ferroptosis, a new form of regulated cell death, results from the iron-dependent accumulation of lipid peroxides that are associated with reactive oxygen species. However, it remains unclear how hydroxyl radical ( • OH) and cellular microenvironments such as viscosity alter in this process. Herein, we characterize for the first time the changing behavior of • OH and cytoplasmic viscosity during ferroptosis using a dual-functional fluorescence probe (H−V) that is designed via the molecular rotor strategy and the unique aromatic hydroxylation of • OH. Probe H−V shows completely separate spectral responses to • OH and viscosity with high sensitivity and selectivity, thereby achieving the detection of • OH and viscosity in two independent channels without spectral crossinterference. With the probe we find that ferroptosis is accompanied by significant • OH generation and cytoplasmic viscosity increase. Most notably, the raised • OH comprises the majority of the total reactive oxygen species in ferroptosis. H−V is biocompatible, ready to prepare, and may be expected to be used in the study of viscosity and • OH detection in more biosystems.

Small molecular fluorophores in the second near-infrared window (NIR-II) have aroused much interest because of their excellent performance. Herein, a new small molecular NIR-II fluorophore, FM1210, with maximal emission beyond 1200 nm is reported. Compared to the corresponding control fluorophore CF1065, FM1210 exhibits an increase of 145 nm in the emission maximum, which is ascribed to the simultaneous introduction of both a Se atom and amino groups into the benzo[1,2-c:4,5-c′]bis([1,2,5]thiadiazole) skeleton. This large increase in the maximal emission enables FM1210 to be capable of in vivo imaging with lower autofluorescence, higher signal-to-background ratio, and better resolution. Moreover, nanosized FM1210 encapsulated in liposomes possesses passive targeting ability and good water solubility, and is suitable for imaging a tumor and even its vasculature with high signal-to-background ratio.

The upregulation of leucine aminopeptidase in hepatopathy models is imaged in vivo for the first time with a near-infrared fluorescent probe.