Eine aktivierbare Lanthanoid‐Lumineszenzsonde für die zeitgesteuerte Detektion von Nitroreduktase in lebenden Bakterien

Synthetic Peptides with Genetic-Codon-Tailored Affinity for Assembling Tetraspanin CD81 at Cell Interfaces and Inhibiting Cancer Metastasis

Probing biomolecular interactions at cellular interfaces is crucial for understanding and interfering with life processes. Although affinity binders with site specificity for membrane proteins are unparalleled molecular tools, a high demand remains for novel multi-functional ligands. In this study, a synthetic peptide (APQQ) with tight and specific binding to the untargeted extracellular loop of CD81 evolved from a genetically encoded peptide pool. With tailored affinity, APQQ flexibly accesses, site-specifically binds, and forms a complex with CD81, enabling in-situ tracking of the dynamics and activity of this protein in living cells, which has rarely been explored because of the lack of ligands. Furthermore, APQQ triggers the relocalization of CD81 from diffuse to densely clustered at cell junctions and modulates the interplay of membrane proteins at cellular interfaces. Motivated by these, efficient suppression of cancer cell migration, and inhibition of breast cancer metastasis were achieved in vivo.

Nitroreductase-Responsive Photosensitizers for Selective Imaging and Photo-Inactivation of Intracellular Bacteria

Intracellular Staphylococcus aureus (S. aureus), especially the methicillin resistant staphylococcus aureus (MRSA), are difficult to detect and eradicate due to the protection by the host cells. Antibacterial photodynamic therapy (aPDT) offers promise in treating intracellular bacteria, provided that selective damage to the bacteria ranther than host cells can be realized. According to the different nitroreductase (NTR) levels in mammalian cells and S. aureus, herein NTR-responsive photosensitizers (PSs) (T)CyI-NO2 were designed and synthesized. The emission and 1O2 generation of (T)CyI-NO2 are quenched by the 4-nitrobenzyl group, but can be specifically switched on by bacterial NTR. Therefore, selective imaging and photo-inactivation of intracellular S. aureus and MRSA were achieved. Our findings may pave the way for the development of more efficient and selective aPDT agents to combat intractable intracellular infections.

Time-Resolved Luminescent Sensing and Imaging for Enzyme Catalytic Activity Based on Responsive Probes

Enzymes, as a kind of biomacromolecules, play an important role in many physiological processes and relate directly to various diseases. Developing an efficient detection method for enzyme activity is important to achieve early diagnosis of enzyme-relevant diseases and high throughput screening of potential enzyme-relevant drugs. Time-resolved luminescence assay provide a high accuracy and signal-to-noise ratios detection methods for enzyme activity, which has been widely used in high throughput screening of enzyme-relevant drugs and diagnosis of enzyme-relevant diseases. Inspired by these advantages, various responsive probes based on metal complexes and metal-free organic compounds have been developed for time-resolved bioimaging and biosensing of enzyme activity owing to their long luminescence lifetimes, high quantum yields and photostability. In this review, we comprehensively reviewed metal complex- and metal-free organic compound-based responsive probes applied to detect enzyme activity through time-resolved imaging, including their design strategies and sensing principles. Current challenges and future prospects in this rapidly growing field are also discussed.

Recent Advances in Fluorescent Probes for Flavinase Activity: Design and Applications

Flavinases, including monoamine oxidase (MAO-A/MAO-B), quinone oxidoreductase (NQO1), thioredoxin reductase (TrxR), nitroreductase (NTR) and so on, are important redox enzymes in organisms. They are considered as biomarkers of cell energy metabolism and cell vitality. Importantly, their aberrant expression is related to various disease processes. Therefore, the accurate measurement of flavinase is useful for the early diagnosis of diseases, which has aroused great concern in the scientific community. Various methods are also available for the detection of flavinases, fluorescence probes are considered to be one of the best detection methods due to their easy and accurate sensing capability. This review aims to introduce the advances in the design and application of flavinase probes in the last five years. This study focuses on analyzing the design strategies and reaction mechanisms of flavinases fluorescent probes and discusses the current challenges, which will further advance the development of diagnostic and therapeutic approaches for flavinase-related diseases.

A General Approach to Design Dual Ratiometric Fluorescent and Photoacoustic Probes for Quantitatively Visualizing Tumor Hypoxia Levels In Vivo

Herein, we describe an energy balance strategy between fluorescence and photoacoustic effects by sulfur substitution to transform existing hemicyanine dyes (Cy) into optimized NIRF/PA dual ratiometric scaffolds. Based on this optimized scaffold, we reported the first dual-ratio response of nitroreductase probe AS-Cy-NO₂ , which allows quantitative visualization of tumor hypoxia in vivo. AS-Cy-NO₂ , composed of a new NIRF/PA scaffold thioxanthene-hemicyanine (AS-Cy-1) and a 4-nitrobenzene moiety, showed a 10-fold ratiometric NIRF enhancement (I₇₇₃ /I₇₃₃ ) and 2.4-fold ratiometric PA enhancement (PA₇₃₀ /PA₆₇₀ ) upon activation by a biomarker (nitroreductase, NTR) associated with tumor hypoxia. Moreover, the dual ratiometric NIRF/PA imaging accurately quantified the hypoxia extent with high sensitivity and high imaging depth in xenograft breast cancer models. More importantly, the 3D maximal intensity projection (MIP) PA images of the probe can precisely differentiate the highly heterogeneous oxygen distribution in solid tumor. Thus, this study provides a promising NIRF/PA scaffold that may be generalized for the dual ratiometric imaging of other disease-relevant biomarkers.