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The whole picture: Carbon nanodots labeled with two fluorescent dyes have been developed as a tunable ratiometric pH sensor to measure intracellular pH. The nanosensor shows good biocompatibility and cellular dispersibility. Quantitative determinations on intact HeLa cells and pH fluctuations associated with oxidative stress were performed.

A novel sequential ultraviolet (UV)-induced living graft polymerization method has been designed and investigated to modify polymeric materials. This method consists of two steps. In the first step, a surface initiator is formed on a substrate under UV irradiation in the presence of benzophenone (BP) solutions; in the second step, the monomers are grafted to the substrate by a living polymerization initiated by the surface photoinitiator. Hydrophobic porous polypropylene (PP) membranes were made hydrophilic and with negatively charged surface by grafting acrylic acid (AA). Experimental results demonstrated that grafting density and graft polymer chain length can be controlled by choosing the reaction conditions in the first step and in the subsequent step(s) independently. The amount of grafted polymer relative to the total amount of polymer from the novel sequential photoinduced graft polymerization method is 4-fold greater than that of the simultaneous grafting method for the system studied. In addition, a reaction mechanism was proposed and confirmed in the experiments. With regard to the surface initiator formation caused by hydrogen abstraction, the kinetic studies show that the reaction rate has a maximum value which depends on BP concentration. With regard to the graft polymerization in the second step, there is a linear relationship between the graft polymerization rate and the monomer concentration.

Heat stroke is a life-threatening condition, featuring a high body temperature and malfunction of many organ systems. The relationship between heat shock and lysosomes is poorly understood, mainly because of the lack of a suitable research approach. Herein, by incorporating morpholine into a stable hemicyanine skeleton, we develop a new lysosome-targeting near-infrared ratiometric pH probe. In combination with fluorescence imaging, we show for the first time that the lysosomal pH value increases but never decreases during heat shock, which might result from lysosomal membrane permeabilization. We also demonstrate that this lysosomal pH rise is irreversible in living cells. Moreover, the probe is easy to synthesize, and shows superior overall analytical performance as compared to the existing commercial ones. This enhanced performance may enable it to be widely used in more lysosomal models of living cells and in further revealing the mechanisms underlying heat-related pathology.

A new rhodamine B-based fluorescent probe for the hypochlorite anion (OCl(-)) has been designed, synthesized, and characterized. The probe comprises a spectroscopic unit of rhodamine B and an OCl(-)-specific reactive moiety of dibenzoylhydrazine. The probe itself is nearly nonfluorescent because of its spirolactam structure. Upon reaction with OCl(-), however, a largely enhanced fluorescence is produced due to the opening of the spirolactam ring by the oxidation of the exocyclic hydrazide and subsequently the formation of the hydrolytic product rhodamine B. Most notably, the fluorescence-on reaction shows high sensitivity and extremely high selectivity for OCl(-) over other common ions and oxidants, which makes it possible for OCl(-) to be detected directly in their presence. In addition, the reaction mechanism has been investigated and proposed. The OCl(-) anion selectively oxidizes the hydrazo group in the probe, and forms the analogue of dibenzoyl diimide, which in turn hydrolyzes and releases the fluorophore. The reaction mechanism that is described here might be useful in developing excellent spectroscopic probes with cleavable active bonds for other species.

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Reactive sulfur species have received considerable attention due to their various biological functions. Among these molecules, hydrogen polysulfides (H2Sn, n > 1) are recently suggested to be the actual signaling molecules derived from hydrogen sulfide (H2S). Hydrogen polysulfides may also have their own biosynthetic pathways. The research on H2Sn is rapidly growing. However, the detection of H2Sn is still challenging. In this work we report a H2Sn-mediated benzodithiolone formation under mild conditions. Based on this reaction, specific fluorescent probes for H2Sn are prepared and evaluated. The probe DSP-3 shows good selectivity and sensitivity for H2Sn.

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.