Design strategies for tetrazine fluorogenic probes for bioorthogonal imaging

Recent advances in developing bioorthogonally activatable photosensitizers for photodynamic therapy

Photodynamic therapy (PDT) is a promising and powerful cancer therapeutic modality, which can generate cytotoxic reactive oxygen species (ROS) from light-irradiated photosensitizers (PSs) to eradicate tumors. To overcome the drawbacks of currently used PSs, researchers have leveraged the advantages of bioorthogonal reactions to design diverse bioorthogonally activatable photosensitizers with excellent tumor selectivity, high ROS generation controllability, and low adverse effect for effective antitumor photodynamic therapy. In this review, we comprehensively summarize and highlight the recent advances in the development of bioorthogonally activatable photosensitizers, including the structure types, designing strategies, activation patterns, photophysical properties, ROS generation efficiency, in vitro and in vivo activities, biological applications, and limitations. We also provide directions and perspectives to address the therapeutic challenges of bioorthogonally activatable photosensitizers for promoting clinical applications. We believe that the principles summarized here will offer useful references for further development of next-generation advanced intelligent photosensitizers and related strategies to realize precise and efficient tumor treatment in the future.

Bright and Versatile Azetidinecarboxamide-Based Fluorophore-Ligand Conjugates for High-Resolution Cell Imaging

Fluorophore-ligand conjugates play a pivotal role in cellular imaging, providing high target specificity. However, simultaneously achieving conjugates with high brightness and ligand-targeting diversity presents significant challenges. Traditional strategies often require complex, multistep modifications for fluorophore enhancement and ligand conjugation. Here, we present an azetidinecarboxamide strategy that addresses these challenges by integrating brightness enhancement and ligand conjugation capabilities within a single molecular framework. The azetidinecarboxamide core suppresses twisted intramolecular charge transfer (TICT), thereby enhancing fluorescence quantum yield. Its carbonyl group provides a versatile site for conjugating a wide range of targeting ligands, enabling the rapid development of diverse and tunable fluorophore-ligand conjugates. This streamlined approach reduces synthetic complexity, accelerates probe development, and is compatible with a wide variety of fluorophores, such as coumarin, naphthalimide, NBD, rhodol, rhodamine, and silicon-rhodamine, facilitating the creation of high-performance, multifunctional probes for advanced cellular imaging.

Tuning Tetrazine Substituents to Enhance Vinyltetrazine Labeling Performance

The site-specific labeling of peptides and proteins is a powerful tool for investigating biological processes. It is demonstrated that the powerful thiol-specific labeling reagent vinyltetrazine activates prodrugs and enables 18F and near-infrared dual-modality imaging. It is predicted that substitutions at the 3-position of tetrazine can affect the labeling efficiency, bioorthogonal kinetics, and stability. Six vinyltetrazines with different 3-position modifications exhibit rapid labeling and, subsequently, bioorthogonal kinetics and excellent stability. Vinyltetrazine labeling modifies the charge characteristics and lipophilicity of target peptides, thereby improving cellular uptake. This research on tuning tetrazine substituents will aid in the construction of a comprehensive vinyltetrazine library, leading to the development of new peptide conjugates and pretargeted immuno-positron emission tomography (immune-PET) imaging.

A Fluorescent Probe for Convenient Visual Detection of Glyphosate Contamination in Water, Soil, and Vegetable Samples

Glyphosate, a widely used herbicide, has raised significant environmental and health concerns due to its persistence in food and environmental matrices. Accurate and sensitive detection methods are essential for monitoring glyphosate contamination and ensuring safety. In this study, a fluorescent probe (DSG-Cu[II]) has been developed for the sensitive and selective detection and monitoring of glyphosate. The fluorophore for making the probe is synthesized through the reaction between dansyl chloride and glycine, forming the fluorophore (DSG) capable of binding copper ions (Cu[II]). The resulting DSG-Cu[II] complex functions via an "off-on" fluorescence mechanism, wherein glyphosate competitively displaces Cu[II], restoring fluorescence. This approach demonstrates high sensitivity and rapid response, with a detection limit of 35 nM and a response time of 30 s. Furthermore, DSG-Cu[II] was successfully applied in real sample analysis, confirming its practical applicability. Additionally, test strips incorporating DSG-Cu[II] enabled visual detection, highlighting its potential for on-site monitoring. This study presents an efficient, selective, and rapid fluorescence-based method for glyphosate detection, contributing to improved environmental and food safety monitoring.