Extracellular vesicles containing fullerene derivatives prepared by an exchange reaction for photodynamic therapy

Extracellular vesicles (EVs) have excellent biocompatibility and long retention times in the circulation and have consequently been expected to be useful as drug-delivery systems. However, their applications have been limited because of the inability to introduce hydrophobic compounds to EVs without the use of harmful organic solvents. Herein, we developed an organic-solvent-free drug-loading technique based on the host exchange reaction. We demonstrated that the exchange reaction enabled quantitative loading of EVs with highly concentrated (0.1 mM) hydrophobic fullerene derivatives. Fullerene derivative-loaded EVs (EVs/C60) could eliminate cancer cell lines more efficiently than fullerene derivative-loaded liposomes (Lip/C60). Moreover, the photodynamic activity of EVs/C60 was fivefold higher than that of the clinically available photosensitizer photofrin. EVs/C60 could efficiently suppress tumor growth in tumor-xenograft model mice.

Activity-Based Fluorescent Probes for Hydrogen Sulfide and Related Reactive Sulfur Species

Hydrogen sulfide (H2S) is not only a well-established toxic gas but also an important small molecule bioregulator in all kingdoms of life. In contemporary biology, H2S is often classified as a "gasotransmitter," meaning that it is an endogenously produced membrane permeable gas that carries out essential cellular processes. Fluorescent probes for H2S and related reactive sulfur species (RSS) detection provide an important cornerstone for investigating the multifaceted roles of these important small molecules in complex biological systems. A now common approach to develop such tools is to develop "activity-based probes" that couple a specific H2S-mediated chemical reaction to a fluorescent output. This Review covers the different types of such probes and also highlights the chemical mechanisms by which each probe type is activated by specific RSS. Common examples include reduction of oxidized nitrogen motifs, disulfide exchange, electrophilic reactions, metal precipitation, and metal coordination. In addition, we also outline complementary activity-based probes for imaging reductant-labile and sulfane sulfur species, including persulfides and polysulfides. For probes highlighted in this Review, we focus on small molecule systems with demonstrated compatibility in cellular systems or related applications. Building from breadth of reported activity-based strategies and application, we also highlight key unmet challenges and future opportunities for advancing activity-based probes for H2S and related RSS.

NBD-Based Environment-Sensitive Fluorescent Probes for the Human Ether-a-Go-Go-Related Gene Potassium Channel

Three environment-sensitive probes were developed for the hERG channel based on the nitrobenzoxadiazole fluorophore herein. After careful evaluation, probes M1 and M3 were found to have a high affinity for imaging the hERG channel in the cell-based experiment. Compared with other fluorescent labeling technologies (such as fluorescent proteins), these probes afford a convenient and economical method to determine hERG channel in vitro and in cellulo. Therefore, these probes are expected to be applicable for usage in physiological and pathological studies of hERG channels and have the potential to establish a screening system for hERG channels.

Heterocyclic N-Oxides as Small-Molecule Fluorogenic Scaffolds: Rational Design and Applications of Their "On-Off" Fluorescence

Small-molecule fluorescent probes are powerful tools in chemical analysis and biological imaging. However, as the foundation of probe design, the meager existing set of core fluorophores have largely limited the diversity of current probes. Consequently, there is a high demand to discover fluorophores with new scaffolds and optimize the existing fluorophores. Here, we put forward a facile strategy of heterocyclic N-oxidation to address these challenges. The introduced N-O bond reconstructs the electron "push-pull" system of heterocyclic scaffolds and dramatically improves their photophysical properties by red-shifting the spectra and increasing the Stokes shift. Meanwhile, the heterocyclic N-O bond also enables a function of the fluorescence switch. It can turn on the fluorescence of pyridine and increase the fluorescence of quinoline and, conversely, decrease the fluorescence of acridines and resorufin. As a further practical application, we successfully utilized the quinoline N-oxide scaffold to design fluorogenic probes for H₂S (8) and formaldehyde (FA, 9). Given their ultraviolet-visible spectra, both probes with high selectivity and sensitivity could be conveniently used in the naked eye detection of target analytes under illumination with a portable UV lamp. More interestingly, the probes could be effectively used in the imaging of nuclear and cytoplasmic H₂S or nuclear and perinuclear FA. This potentially overcomes the weaknesses of existing H₂S or FA probes that can only work in the cytoplasm. These interesting findings demonstrate the ability to rapidly expand and optimize the existing fluorophore library through heterocyclic N-oxidation.

AND-Logic Based Fluorescent Probe for Selective Detection of Lysosomal Bisulfite in Living Cells

Sulfur dioxide (SO₂) plays significant roles in regulating cell apotosis and inflammation. However, there are complex interactions between small biomolecules in cells, and the identification of these coexisting biomarkers remains a challenge. Herein, we report an AND logic gate based fluorescent probe (NY-Lyso), operating by responding to pH differences between organelles in cell and selectively reacting with bisulfite (HSO₃^-). This approach allows the fluorescence of the probe to remain silent under neutral or alkaline conditions, notably, is activated by costimulation of lower pH and bisulfite. Furthermore, it was confirmed to be biocompatible and could be employed to monitor HSO₃^- in lysosomes of living cells. The proposed method demonstrated more practical and outstanding capabilities in targeted and real-time monitoring, providing an effective optical tool for biomarker sensing.

Novel long-wavelength emissive lysosome-targeting ratiometric fluorescent probes for imaging in live cells

Lysosomes are acidic organelles containing many hydrolytic enzymes responsible for degrading macromolecules.