Amplified detection of β-glucuronidase activity based on cascade catalysis

β-Glucuronidase (β-GLU) plays a pivotal role in disease progression and serves both as a biomarker and a therapeutic target. Novel strategies for β-GLU detection are highly desirable. Here, we present a cascade catalytic strategy for amplified detection of β-GLU activity. Using 8-hydroxyquinoline-β-D-glucuronide (8-HQG) as the substrate, β-GLU enzymatically releases 8-hydroxyquinoline (8-HQ), which effectively activates the catalytic activity of Co2+, thereby facilitating the H2O2-dependent oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). This strategy enables sensitive colorimetric detection of β-GLU activity with a limit of detection (LOD) of 0.022 U/mL. The results demonstrate the potential of our cascade catalytic system not only for β-GLU detection but also for inhibitor selection and enhancing treatment for related diseases.

Tumor-specific cathepsin B-triggered fluorescence imaging and prodrug activation

Bioorthogonal activation chemistries have great potential in the development of novel drug treatments due to their versatility, tunability, and the ability to generate therapies with improved spatial targeting. The upregulation of Cathepsin B is highly correlated with the development of cancers, however, few fluorescent probes or prodrugs-based on Cathepsin B activity have demonstrated high tumor selectivity, since Cathepsin B is expressed in a variety of normal tissues. In this study, we report a strain-promoted azide-alkyne cycloaddition-activation strategy whereby a para-azido safety-catch linker is triggered by the tumor locating Biotin-TCO (trans-cyclooctene) conjugate, with subsequent tumor-specific Cathepsin B-triggered activation, generating a fluorescent reporter/cytotoxic drug, with high tumor selectivity. Our results suggest that this dual AND-Gate strategy of orthogonal Biotin AND Cathepsin B action would be advantageous for tumor-specific fluorescence labelling, fluorescence-guided surgery and targeted treatment.

Enhancing clinical precision in lung cancer tissue biopsy through elevated response-threshold of an endoplasmic reticulum-targeted fluorogenic probe

Lung carcinoma is the leading cause of mortality globally, posing a significant public health concern. Fluorescent-mediated tumor imaging is emerging as a novel diagnostic and therapeutic approach in clinical practice. Nevertheless, traditional probes lack accuracy in diagnosing tumors due to the overlap in baseline values of certain tumor biomarkers between normal and tumor cells as both exhibit turn-on fluorescence, rendering it impossible to distinguish tumor tissue from normal tissue with high resolution. We introduce a sensing strategy that constructs a probe with an elevated biomarker response-threshold and targeting ability for the endoplasmic reticulum (ER), enabling precise distinction between tumor and normal cells, and successfully develop such a probe. Elevating the response-threshold is advantageous in minimizing interference from baseline values of biomarkers in normal cells. Additionally, targeting the ER ensures that the probe's response range is consistent with the biomarker content in the ER, collectively enhancing differentiation between normal and cancer cells. Using this novel probe, a distinct bright fluorescence signal from tumors could be observed in confocal imaging of tumor tissues from tumor-bearing mice after intravenous injection, in stark contrast to the limited fluorescence emanating from normal tissues. Furthermore, this probe demonstrated exceptional precision in distinguishing clinical lung cancer tissue from para-cancer tissue. This work presents a more reliable tumor detection strategy, capable of accurate diagnosis even when the biomarker is highly expressed in both normal and tumor tissues. It promises to be a valuable tool for future clinical applications, particularly in intraoperative assisted resection.

Small molecular fluorescent probes featuring protein-assisted functional amplification for improved biosensing and cancer therapeutics

In recent years, small molecular fluorescent probes have significantly advanced biosensing and cancer therapy, enabling applications such as target detection, cellular imaging, fluorescence-guided surgery, and phototherapy. However, conventional small molecular probes face limitations, including low biocompatibility, poor stability, and weak signal intensity. Protein-coordinated fluorescent probes have emerged as a promising solution, leveraging protein-assisted functional amplification to address these challenges. Mechanisms such as environmental shielding, conformational restriction, charge stabilization, and increased local concentration collectively enhance fluorescence emission and phototherapeutic efficacy. This article reviews recent progress (primarily within the last five years) in protein-coordinated fluorescent probes for biosensing and cancer therapy. It begins with a systematic summary of the interaction strategies between proteins and fluorescent probes and details key mechanisms behind protein-assisted functional amplification. Subsequently, the applications of these probes in biosensing and cancer therapy are comprehensively concluded. Finally, current challenges and future prospects are discussed in depth. This review aims to refine design strategies for protein-coordinated fluorescent probes and inspire innovative approaches in biosensing and cancer therapy.

Icing on the Cake: Integrating Optical Fiber with Second Near-Infrared Aggregation-Induced Emission Luminogen for Exceptional Phototheranostics of Bladder Cancer

Bladder cancer is a common urological malignancy characterized by high morbidity, high recurrence rate and high mortality, imposing heavy burdens on patients mentally and financially. The research pioneers a diagnostic and therapeutic approach that integrates a second near-infrared (NIR-II) multimodal phototheranostic platform with optical fiber-mediated interventional phototherapy strategy, to implement a comprehensive diagnosis and "inside-out" treatment of bladder cancer. The proposed molecule, namely BTO-TTQ, is elaborately designed through electron donor/π-bridge engineering and demonstrates satisfying NIR-II emission with aggregation-induced emission features, high photothermal conversion efficiency, and prominent generation of type I reactive oxygen species. Quantum chemical calculations and molecular dynamics simulations are employed to deeply elucidate the energy dissipation pathways of the excited state and the impact of intramolecular motion on their photophysical properties. Furthermore, under the guidance of NIR-II fluorescent-photoacoustic-photothermal trimodal imaging, hyaluronic acid-modified BTO-TTQ nanoparticles exhibit exceptional performance in optical fiber-mediated interventional phototherapy for air-pouch bladder cancer models. This study thus brings a new insight into the development of superior versatile phototheranostics for clinical theranostics of bladder cancer.

An indolium-based near-infrared fluorescent probe for non-invasive real-time monitoring of gastric pH in vitro and in vivo

Abnormal gastric acidity is closely linked to severe gastrointestinal diseases, making the real-time monitoring of gastric pH critical for investigating stomach-related physiological and pathological processes, diagnosing related diseases, and evaluating drug efficacy. In this study, we developed a near-infrared (NIR) fluorescent probe, named Hcy-pH, by conjugating a p-dimethylaminophenyl moiety with an indolium fluorophore via extended double bonds. The probe displayed significant NIR fluorescence at 820 nm in a PBS buffer, with a large Stokes shift of 240 nm. The fluorescence intensity of the probe decreased progressively as the pH decreased from 4.0 to 2.5, with a calculated pKa of 2.98. Hcy-pH exhibited excellent biocompatibility and enabled the visualization of pH fluctuations in vitro by living HeLa cells. Moreover, the non-invasive monitoring of gastric pH in vivo was achieved in live mice, underscoring its great potential for studying stomach-related diseases and evaluating related pharmaceuticals.

A novel boron-stereogenic fluorophore with dual-state circular polarization luminescence via a self-dispersing strategy

Molecular engineering is a reliable approach for the development of circularly polarized luminescence (CPL) materials for various applications. However, creating dual-state CPL platforms that possess chirality while achieving a delicate balance between molecular rigidity and flexibility remains a formidable challenge. In this study, a novel bisarylboron-anchored pyrrolylsalicylhydrazone (BOPSH) platform was synthesized via a facile "one-pot" condensation. These key aryl-boron substituents not only provide structural rigidity to the fluorophore, enhancing the bright emission and suppressing emission quenching from π-π stacking in solid states due to their twisting and bulky steric effects, but also generate a boron-stereogenic center and enable strong CPL by promoting intramolecular charge-transfer transitions. As a result, these BOPSHs show intense absorption and strong dual-state emissions in both solution and solid states (with Φ PL value approaching unity), emitting across the visible region with excellent chemical, photostability, and thermal stability. Meanwhile, their enantiomers display dual-state CPL performance, with luminescence dissymmetry factors (g lum) up to 9.40 × 10-3, and CP electroluminescence (EL) with a dissymmetry factor (g EL) of 3.07 × 10-3, along with excellent maximum external quantum efficiencies (η ext,max) of 5.0%, approaching the theoretical limit for fluorescent molecules. We expect our study to break new ground in the construction of chiral dual-state materials with diverse structures.

Manipulating ICG J-Aggregation and Disaggregation for Imaging-Guided Cancer Therapy with Self-Reporting Efficiency

Integrating imaging guided therapy and therapeutic effect self-reporting would highly benefit clinic applications. J-type aggregates of organic dyes with corresponding photothermal effect have made them popular agents for photoacoustic (PA) imaging and photothermal therapy (PTT). However, approaches to manipulate the disaggregation of J-aggregate with corresponding organic dye fluorescence recovery have rarely been reported, which limits the full exploration of J-aggregate in therapeutic applications. Herein, indocyanine green (ICG) J-aggregate is designed in a micelle structure (J-ICG-Micelle) by co-assembling ICG with DSPE-Pep-PEG, which contains peptide KADEVDAC that recognized and cleaved by caspase-3. Taking advantages of the red-shifted absorbance of J-ICG-Micelle, it achieves PA imaging navigated delivery process with an indication of tumor accumulation time and position to perform PTT. Corresponding cell apoptosis and caspase-3 generation cleaves peptide KADEVDAC and results in fluorescence recovery of ICG, which self-reports therapeutic effect in real time, and the intensity for fluorescence recovery demonstrates similar tendency as H&E staining at tumor sections. The as-presented J-ICG-Micelle would have a promising contribution to precise cancer therapy.

A dual-cascade-activatable molecular probe with microenvironment-adapted performance for accurate differentiation of hepatopathy

Fluorescence imaging utilizing biomarker-activatable fluorescent probes has emerged as a powerful tool for the precise and early diagnosis of hepatopathy. However, the development of effective molecular probes remains challenging due to limitations, such as single-stimulus responsiveness and incompatible with microenvironment characteristic of hepatopathy. These limitations often result in a lower signal-to-noise ratio, false positives and ultimately reduced diagnostic accuracy. In this study, we developed a novel dual-lock-controlled fluorescent probe (Hdual) based on basic blue 3 dye. This probe was designed to be sequentially activated by two potential hepatopathy biomarkers, leucine aminopeptidase (LAP) and monoamine oxidase (MAO), through a cascade mechanism. Moreover, after addition LAP and MAO, Hdual exhibited a linear fluorescence change within a pH range of 6.2-6.8, ensuring high compatibility with the weakly acidic microenvironment characteristic of hepatopathy. The dual-cascade-activatable design, combined with the probe's microenvironment-adapted property, enabled Hdual to achieve a significantly higher target-to-noise ratio (T/N) of 2.40 in in vivo imaging for drug-induced liver injury, compared to "single-locked" probe (T/N < 0.79). Notably, Hdual demonstrated the ability to differentiate between cirrhotic and hepatitis B samples by analyzing patient blood samples through both fluorescent imaging and a distinct colorimetric change, observable either visually or via smartphone-based color analysis. These findings highlight Hdual's high specificity and accuracy in fluorescence imaging-based detection, underscoring its potential to improve the early diagnosis of hepatopathy.

Proteoglycan-degrading enzymes engineered for enhanced tumor microenvironment interaction in renal cell carcinoma

This work optimized proteoglycan-degrading enzymes through targeted mutagenesis to enhance their interaction with the tumor microenvironment in Renal Cell Carcinoma (RCC). A comprehensive mutagenesis approach identified 60 key mutations significantly improving enzymatic activity, stability, and structural integrity. When compared to Wild Type (WT) enzyme, a remarkable increase in specific activity by 35 % (p < 0.001) and a considerable decrease in the Km values for hyaluronidases from 2.5 mM to 1.5 mM (p < 0.05), as a result of these modifications. Computational methods are then employed to analyze the active site of the enzymes to detect potential residues that may alter. These computational techniques include molecular docking and protein structure prediction. The structural models of the enzymes are created by utilizing homology modeling and crystallography. These models demonstrate the spatial arrangement of the amino acid enzymes. It also illustrated the specific mutations to improve the potential of enzymes to relate to the Extracellular Matrix (ECM) of tumors. The computational screening methods effectively predicted how the modifications impact enzyme catalytic efficiency and stability. The modified enzymes retained 85 % of the enzyme activity, while the WT retained 60 %. Thus, the modified enzymes demonstrated better thermal stability than WT. Vitro test analyses show that the proteoglycan breakdown was significantly reduced by 70 % (p < 0.001), and for effective proteoglycan breakdown, hyaluronidase concentration is needed. This work proposed a novel therapeutic approach called proteoglycan-degrading enzymes for the treatment of RCC. These proteoglycan-degrading enzymes are more stable and effective for treating RCC, as demonstrated in the outcomes. Customized proteoglycan-degrading enzymes make the therapy more effective. The effective breakdown of the tumor's ECM in RCC models establishes this customized proteoglycan-degrading enzyme. These enzymes are effective for this customized cancer treatment as they improve stability, activity, and interaction with the TME.

Recent advances in bioresponsive macrocyclic gadolinium(III) complexes for MR imaging and therapy

Magnetic resonance (MR) imaging is a non-invasive clinical diagnostic modality that provides anatomical and physiological information with sub-millimetre spatial resolution at the organ and tissue levels. It utilizes the relaxation times (T1 and T2) of protons in water to generate MR images. However, the intrinsic MR contrast produced by water relaxation in organs and tissues is limited. To enhance the sensitivity and specificity of MR imaging, about 30%-45% of all clinical MR diagnoses need to use contrast media. Currently, all clinically approved MR contrast agents are linear or macrocyclic gadolinium(III) (Gd(III)) complexes, which are not specific to particular biological events. Due to the relatively high potential for releasing toxic free Gd(III), linear Gd(III) complexes raise safety concerns, making macrocyclic Gd(III) probes the preferred choice for clinical MR imaging without acute safety issues. To enhance the capability of MR imaging for detecting dynamic biological processes and conditions, many bioresponsive macrocyclic Gd(III) complexes capable of targeting diverse biomarkers have been developed. This review provides a concise and timely summary of bioresponsive macrocyclic Gd(III) contrast agents, particularly those developed between 2019 and 2024. We focus on three major types of Gd(III) agent that respond specifically to changes in pH, chemicals, and enzymes, highlighting their molecular design strategies, proton-relaxivity responses, and applications in in vitro and in vivo MR imaging for monitoring specific biomedical conditions and therapies.

Dual-emission fluorescent probe with sequential two-step ESIPT activation mechanism for selective hydrazine detection and multifunctional applications

Hydrazine is a commonly used chemical in various industries, including pharmaceuticals, agriculture, and aerospace. However, its high toxicity may cause serious harm to the natural environments and human health. The development of new methods for sensitive and selective detection of hydrazine is of great significance. In this study, we present a fluorescent probe that employs a unique two-step excited-state intramolecular proton transfer (ESIPT) activation mechanism for hydrazine detection. This probe integrates a phthalimide group into benzothiazole scaffold with its fluorescence initially quenched due to the inhibition of ESIPT process and photo-induced electron transfer (OFF state). Upon exposure to hydrazine, the nucleophilic cleavage of the phthalimide group activates the first ESIPT process, yielding yellow emission (ON1 state). A subsequent deprotection step triggers the second ESIPT process, producing blue fluorescence (ON2 state). These three states fluorescent change along with dual-emission signal output provide a highly sensitive and reliable method for hydrazine detection and monitoring, with a limit of detection (LOD) of 18 nM. Moreover, this probe showed versatile applications in environmental monitoring, food sample analysis, plant imaging, and bioimaging, including a convenient smartphone-assisted quantitative assay. The dual-activation mechanism offers valuable insights for the design of novel ESIPT probes, paving the way for promoting their applications in chemical, biological, and environmental fields.

Recent Advances in Enzyme-Activated Dual-Locked Probes for Biological Applications

Enzymes catalyze reactions involved in diverse physiological, pathological, and pharmacological processes. By employing the optical probe, fluorescence imaging enables non-invasive, real-time detection and assessment of disease states based on enzymatic activity. However, most enzyme-activated probes are single-locked probes that respond to a single biomarker. In comparison to single-locked probes, enzyme-activated dual-locked probes can effectively minimize the occurrence of false-positive signals, circumvent the problem of low specificity associated with biologically active substances, and facilitate precise imaging. This review systematically summarizes the design and application of dual-locked probes in disease diagnosis, with the aim of providing inspiration for researchers in the field.

Noncovalent Interaction-Based Probe Design for PET-Facilitated Fluorescence Sensing of Synthetic Cannabinoids

Due to the structural diversity and rapid iteration of synthetic cannabinoids (SCs), their detection presents a challenging issue. Here, based on the structure and physicochemical property analysis of a typical SC, MDMB-CHMICA, four fluorescent probes were designed by introducing the recognition groups and fluorescence regulation groups on carbazole. It is found that the electron-withdrawing and conjugation-extending effect of the nitro group reduced the LUMO energy level and thereby narrowed the HOMO-LUMO energy gap, resulting in a red-shift of the fluorescence emission. As a result, the intramolecular charge transfer mechanism of the probe helps to lead to stronger fluorescence with a greater charge transfer distance. Two probes with stronger fluorescence show multiple noncovalent interactions with MDMB-CHMICA and efficient fluorescence quenching sensing through photoinduced electron transfer. This study is expected to shed light on the exploration of fluorescent probes from the analytes' physicochemical nature and would be helpful for new psychoactive substance detection.

Gadolinium Functionalized Carbon Dot Complexes for Dual-Modal Imaging: Structure, Performance, and Applications

Gadolinium functionalized carbon dot complexes (Gd-CDs) have both the fluorescent properties of carbon dots and the magnetic characteristics of gadolinium ions, exhibiting excellent biocompatibility, high spatial resolution, high sensitivity, and deep tissue penetration in bioimaging. As fluorescence (FL) and magnetic resonance imaging (MRI) probes, Gd-CDs have attracted significant attention in dual-modal biological imaging. This review summarizes recent advances in Gd-CDs, focusing on their structure, optical and magnetic properties, and applications in dual-modal imaging. First, according to the different existing forms of gadolinium in carbon dots, the structures of Gd-CDs are categorized into chelation, electrostatic interaction, and encapsulation. Second, the mechanisms and performances of Gd-CDs in dual-modal imaging are introduced in detail. The reported Gd-CDs have a maximum quantum yield of 69.86%, with a fluorescence emission wavelength reaching up to 625 nm, and the optimum longitudinal and transverse relaxivity rates are 35.39 and 115.6 mM-1 s-1, respectively, showing excellent FL/MRI capacities. Subsequently, the progress in their applications in dual-modal cellular imaging, in vivo imaging, and integrated cancer diagnosis and therapy is reviewed. Finally, the challenges and issues faced by Gd-CDs in their development are summarized, providing new insights for their controlled synthesis and widespread application in the biomedical field of dual-modal imaging.

Evodiamine-Based Nitroreductase Responsive Theranostic Agents for Treatment of Colon Cancer

Hypoxia is a state of low oxygen tension that is found in numerous solid tumors. Generally, nitroreductase (NTR) is overexpressed and directly correlated with the hypoxic status in solid tumors, supporting the hypothesis that prodrug could be activated by intracellular NTR and lead to potential antitumor therapy. Herein, evodiamine-based hypoxia-targeting theranostic agents were developed to enhance the antitumor efficacy. These agents are activated by NTR-mediated p-nitrobenzyl reduction, enabling simultaneous fluorophore activation for imaging and therapeutic agent (3-fluoro-10-hydroxyl-evodiamine) release for solid tumor treatment. After a systemic test, these theranostic agents were verified to be selectively activated by NTR with excellent fluorescence properties and antitumor potency. In particular, Probe-2 exhibited excellent in vivo antitumor activity (tumor growth inhibition value (TGI) = 76.1%) in HCT116 xenograft nude mice with favorable tumor-targeted properties and low toxicity. Thus, this NTR-responsive theranostic agent provides a platform for constructing prodrugs to release monitoring and active substances controlled by the hypoxic status.

Small-Molecule Fluorescent Probes for Butyrylcholinesterase

Butyrylcholinesterase plays an indispensable role in organisms, and its abnormal expression poses a significant threat to human health and safety, covering various aspects including liver-related diseases, diabetes, obesity, cardiovascular and cerebrovascular diseases, and neurodegenerative diseases. In addition, toxic substances such as organophosphorus and carbamate pesticides markedly inhibit BChE activity. BChE activity serves as a critical parameter for the clinical diagnosis of acute organophosphorus pesticide poisoning and the evaluation of organophosphorus and carbamate pesticide residues. Therefore, the accurate and reliable detection of butyrylcholinesterase activity is particularly urgent and important for in-depth analysis of its biological function, diagnosis and therapy of related diseases, drug screening and sensitive detection of pesticide residues. Fluorescent probes have become a promising tool for sensing and imaging of butyrylcholinesterase, due to its advantages of high spatio-temporal resolution, high selectivity, non-invasive, high sensitivity, and tailored molecule structures. Here, this paper provides a comprehensive overview of the research progress in the sensing, imaging and therapy of butyrylcholinesterase utilizing fluorescent probes. This paper might be a useful guideline for researchers to design new high-performance fluorescence probes for BChE, and making further contributions to this intriguing field.

A Water-Soluble Small-Molecule Fluorescent Probe for Selective Imaging of Colorectal Cancer with High Biosafety

Early diagnosis of colorectal cancer (CRC), a malignant tumor with high incidence and mortality rates worldwide, can significantly reduce both its incidence and mortality. Among cancer diagnostic methods, tumor fluorescence imaging provides a non-invasive approach, eliminating the need for tissue biopsy and minimizing patient discomfort. In this study, we identified a water-soluble quinolinium molecular fluorescent probe (CYI), which exhibits a dose-dependent quantum yield in PBS solution, reaching 5.96% at a concentration of 20 µM. The results demonstrated that CYI selectively enters CRC cells and maintains stable fluorescence intensity within them by specifically targeting the mitochondria and lysosomes, leading to probe accumulation and enhanced intracellular fluorescence. Importantly, toxicity assays at both the cellular and animal levels confirmed that CYI is highly biocompatible at fluorescence imaging doses, with no toxic effects observed in normal colorectal cells or organisms. This study identifies CYI as a water-soluble molecular fluorescent probe with a high biosafety profile, excellent imaging stability, and preferential uptake by CRC cells, demonstrating strong potential for early CRC screening and in vivo monitoring.

Highly Specific Miniaturized Fluorescent Monoacylglycerol Lipase Probes Enable Translational Research

Monoacylglycerol lipase (MAGL) is the pivotal catabolic enzyme responsible for signal termination in the endocannabinoid system. Inhibition of MAGL offers unique advantages over the direct activation of cannabinoid receptors in treating cancer, metabolic disorders, and inflammatory diseases. Although specific fluorescent molecular imaging probes are commonly used for the real-time analysis of the localization and distribution of drug targets in cells, they are almost invariably composed of a linker connecting the pharmacophore with a large fluorophore. In this study, we have developed miniaturized fluorescent probes targeting MAGL by incorporating a highly fluorescent boron-dipyrromethene (BODIPY) moiety into the inhibitor structure that interacts with the MAGL active site. These miniaturized fluorescent probes exhibit favorable drug-like properties such as high solubility and permeability, picomolar potency for MAGL across various species, and high cell selectivity and specificity. A range of translational investigations were conducted, including cell-free fluorescence polarization assays, fluorescence-activated cell sorting analysis, and confocal fluorescence microscopy of live cancer cells, live primary neurons, and human-induced pluripotent stem cell-derived brain organoids. Furthermore, the application of red-shifted analogs or 18F positron emission labeling illustrated the significant versatility and adaptability of the fluorescent ligands in various experimental contexts.

Imaging Heterogeneous Patterns of Aminopeptidase N Activity in Hierarchical Tissue Structures Through High-Resolution Whole-Organ 3D Mapping

Enzymes play a crucial role in regulating physiological functions, and abnormal enzyme activity is associated with various pathological conditions. Precise imaging of enzyme activity in tissues, providing detailed spatial and quantitative information, advances our understanding of physiological and pathological processes. Despite their importance, there is still a lack of methods for high-resolution 3D imaging of enzyme activity across entire tissues. In this research, we report a methodology for high-resolution, whole-organ 3D mapping of enzyme activity, which combines tissue clearing with an activity-based covalent chemical probe. Focusing on aminopeptidase N (APN) as a representative target of peptidase, we developed ANA-o-BODIPY, an activity-based covalent fluorescent probe compatible with tissue clearing for imaging APN activity. Upon activation by APN, ANA-o-BODIPY produces a reactive intermediate, aza-quinone methide, which covalently binds to proximal proteins. This covalent probe is successfully utilized to record the location of APN activity during the tissue-clearing process. By combining the probe with tissue clearing, we have achieved high-resolution 3D mapping of APN activity across whole organs for the first time. Moreover, this advancement allowed us to visualize the heterogeneity of APN activity in individual tubular structures and to uncover the inhibitory effects of different APN inhibitors.

Near-Infrared Chemiluminophore Switches Photodynamic Processes via Protein Complexation for Biomarker-Activatable Cancer Therapy

Despite the potential in cancer therapy, phototheranostic agents often face two challenges: limited diagnostic sensitivity due to tissue autofluorescence and suboptimal therapeutic efficacy due to the Type-II photodynamic process with the heavy oxygen reliance. In contrast, chemiluminescent theranostic agents without the requirement of real-time light excitation can address the issue of tissue autofluorescence, which however have been rarely reported for photodynamic therapy (PDT), not to mention less oxygen-dependent Type-I PDT. In this work, we synthesize near-infrared (NIR) chemiluminophores with the specific binding towards human serum albumin (HSA) to form chemiluminophore-protein complex for cancer detection and photodynamic therapy. Interestingly, after the complexation with HSA, the chemiluminescence (CL) intensities of chemiluminophores are enhanced by over 10-fold; meanwhile, the photodynamic process switches from Type-II (singlet-oxygen-generation dominated) to Type-I (superoxide anion and hydroxyl radical dominated), while the previously reported activated chemiluminophore with non-specific HSA binding can't switch photodynamic process. Based on the optimal chemiluminophore, a nitroreductase-activatable CL probe-protein complex is synthesized, which specially turns on its CL and Type-I PDT in hypoxic tumors for precision therapy. Thus, this study provides a complexation strategy to improve phototheranostic performance of chemiluminophores.

FAP-catalyzed in situ self-assembly of magnetic resonance imaging probe for early and precise staging of liver fibrosis

Liver fibrosis is an inevitable stage in the progression of most chronic liver diseases. Early diagnosis and treatment of liver fibrosis are crucial for effectively managing chronic liver conditions. However, there lacks a noninvasive and sensitive imaging method capable of early assessing fibrosis activity. Here, we report a molecular magnetic resonance imaging (MRI) probe for imaging fibroblast activation protein (FAP), which is overexpressed on activated hepatic stellate cells (HSCs) even in very early fibrotic livers. This method relies on FAP-catalyzed in situ self-assembly of its substrate probe that leads to the increase of the rotational correlation time (τR) of probe, thereby notably amplifies T1 MRI signal. Thanks to the superior specificity and efficiency of enzymatic reaction, our method has been validated as highly selective and sensitive to FAP in two liver fibrosis mouse models. By establishing a direct correlation between MRI signals and fibrosis activity, our method enables continuous monitoring of liver fibrotic disease progression and assessment of treatment responses.

Novel functionalized benzimidazole-salicylic acid derivatives: synthesis, photophysical characteristics and biological applications

Although the benzimidazole moiety is a versatile heterocyclic unit that has been widely applied in optical materials and medicinal chemistry, there are few bifunctional small-molecule benzimidazole derivatives with bio-activity and fluorescence. In this work, a series of novel benzimidazole-salicylic acid molecules were designed and synthesized; their optical properties were evaluated and their potential biological application was explored. The representative compound 5q exhibited excellent fluorescence properties, displaying blue imaging in HeLa cells and zebrafish. Additionally, it exhibited high selectivity for Fe3+ ions and demonstrated a notable inhibitory activity with IC50 = 6.86 ± 2.82 μM against SHP1PTP. Further effort was applied to explore the potential capability of compound 5q to reactivate the activity of SHP1 when inhibited by Fe3+ ions, indicating that compound 5q could be a fluorescent modulator to adjust SHP1 enzyme activity in biological systems.

Excited-State-Altering Ratiometric Fluorescent Probes for the Response of β-Galactosidase in Senescent Cells

β-galactosidase (β-Gal) has emerged as a pivotal biomarker for the comprehensive investigation of diseases associated with cellular senescence. The development of a fluorescent sensor is of considerable importance for precisely detecting the activity and spatial distribution of β-Gal. In this study, we developed two excited-state-altering responsive fluorescent sensors (TF1 and TF2) for ratiometric detection of β-Gal. Two TCF dyes, composed of tricyanofuran (TCF) and naphthol units, feature electron "pull-push" systems and are quenched fluorescence by β-Gal. Upon β-Gal hydrolysis, a significant ratiometric shift in absorption from ca. 475 nm to 630 nm is observed, accompanied by the emergence of a fluorescence signal at ca. 660 nm. The enzyme-responsive optical red-shifts are attributed to the excited-state transition from intramolecular charge transfer (ICT) state to local excited (LE) state, which was confirmed by density functional theory (DFT) calculations. Both fluorescent sensors display exceptional sensitivity and selectivity for the response of β-Gal in PBS solution and are capable of tracking β-Gal within senescent A549 cells. This study introduces a framework for developing multimodal optical probes by systematically modulating excited-state properties, demonstrating their utility in senescence studies, diagnostic assay design, and therapeutic assessment.

Sensitive detection of fluid biomarkers using adamantylidene 1,2-dioxetane based chemiluminescent probes

Body fluid analysis is a crucial non-invasive diagnostic tool that offers valuable insights into the body's physiological state and aids in early disease detection. Traditional methods, however, can be costly, time-consuming, and lack sensitivity. To address these issues, fluorescence imaging technology, employing various fluorescent probes, has emerged as a promising alternative. Yet, background fluorescence from compounds in body fluids can interfere with analytical sensitivity. Chemiluminescent probes, particularly Schaap's adamantylidene 1,2-dioxetane based ones, overcome this challenge by eliminating the need for external excitation and enhancing the signal-to-noise ratio. In this feature article, we summarize recent advancements in the design and application of Schaap's adamantylidene 1,2-dioxetane based chemiluminescent probes for detecting analytes in body fluids such as blood, plasma, urine, and sputum. Our discussion covers contributions from both our own research and the work of others, focusing on the detection of fluid biomarkers for specific diseases. Additionally, we discuss the challenges faced and propose future research directions in designing Schaap's adamantylidene 1,2-dioxetane based probes tailored for body fluid analysis. We hope this review inspires further development of chemiluminescent probes suitable for a wide range of body fluid analyses.

Dual-Locked Enzyme-Activatable Fluorescence Probes for Precise Bioimaging

Real-time visualization of endogenous enzymes not only helps reveal the underlying biological principles but also provides pathological information for cancer/disease diagnosis and even treatment guidance. To this end, enzyme-activatable fluorescence probes are frequently fabricated that turn their fluorescence signals "on" exclusively at the enzyme-rich region, thus enabling noninvasive and real-time imaging of enzymes of interest at the molecular level with superior sensitivity and selectivity. However, in a complex biological context, commonly used single enzyme-activatable (i.e., single-locked) probes may suffer from "false positive" signals at healthy tissues and be insufficient to accurately indicate the occurrence of certain diseases. Therefore, dual-locked fluorescence probes have been promoted to address these issues. Using dual enzymes (or an enzyme with another stimulus) as "keys", they permit simultaneous detection of distinct biomarkers, offering significantly enhanced imaging precision toward certain biological events. Considering that recent reviews on these probes remain scarce, we thus provide this review. We summarize the recent progress, particularly highlighting the breakthroughs in the last three years, and discuss the challenges in this field.

Sensing and Imaging Agents for Cyclooxygenase Enzyme

In this concept, we present a comprehensive study on the development and application of COX-2-specific fluorescent probes for cancer imaging and diagnosis. To target cancer cells and measuring cancer-related activities in specific organelles quickly and accurately are crucial factors for early diagnosis and research on cancer pathology and treatment. This concept explores a variety of probes based on indomethacin (IMC), celecoxib, rofecoxib as well as CoxFluor and each one demonstrates unique mechanisms and high selectivity towards COX-2 enzymes. These probes were designed to enhance fluorescence upon binding to COX-2 which enable precise visualization of tumor and inflamed tissues. The research emphasizes the importance of COX-2 as a biomarker in cancer diagnostics, particularly in identifying cancer stem cells and inflamed tissues. This concept highlights the potentiality of these probes in non-invasive imaging techniques which offering significant advancements in cancer diagnosis and monitoring. The in vivo and in vitro experiments, including applications in mouse models and human tissue samples, confirm the efficacy of these probes in providing detailed imaging for clinical and research applications.

Unravelling the recent advancement in fluorescent probes for detection against reactive sulfur species (RSS) in foodstuffs and cell imaging

Sulfur-containing representative HSO3-/SO32-, H2S, and biothiols (Cys, Hcy, and GSH) present in food items and biological organisms have raised substantial global concerns about food safety due to their reactivity and potential health implications. Adhering to international health standards is essential for these compounds; in particular, plenty of challenges exist in ensuring product quality in the beverage industry. Many fluorescent probes are being employed in various spectroscopic techniques and have developed rapidly to selectively detect sulfur-related species in food products and bio-sensing for cell imaging. This comprehensive review provides a detailed overview of a wide range of fluorescent probes designed using different fluorophores for detecting reactive sulfur species (RSS) using spectroscopic techniques. Additionally, the review explores the detection of RSS components (HSO3-/SO32-, H2S, and biothiols) in food products and cell imaging using different cell lines, highlighting the crucial role of fluorescent probes in swiftly detecting these analytes in both natural and biological contexts. Furthermore, the review discusses future trends and perspectives, emphasizing the on-going progress in detecting these analytes in food products and cell imaging using various fluorescent probes.

An innovative fluorescent probe for monitoring of ONOO- in multiple liver-injury models

The liver plays a pivotal role in numerous critical physiological processes, functioning as the body's metabolic and detoxification center. Chronic liver disease can precipitate more severe health complications. The onset and progression of liver disease are often characterized by abnormal concentrations of ONOO-, a highly reactive species whose direct capture and detection in physiological environments pose significant challenges. This work presents an innovative fluorescent probe NAP-ONOO derived from 1,8-naphthalimide, specifically engineered to dynamically monitor fluctuations of ONOO- levels during liver injury. Due to its high biocompatibility, NAP-ONOO enabled to observe varying degrees of ONOO- up-regulation across models of liver inflammatory injury, alcohol-induced damage, and drug-induced hepatotoxicity in cellular systems as well as in zebrafish and mice models. These findings highlight the potential of NAP-ONOO for identifying and detecting the liver injury biomarker ONOO-. Furthermore, NAP-ONOO serves as potent tool for the identification of liver injuries, drug screening, and cellular imaging analyses, thereby promising avenues for future research endeavors.

Biotinylated Viscosity Sensitive Cell Membrane Probe for Targeted Imaging and Precise Visualization of Tumor Cells and Tumors

Cancer is a global health challenge that urgently requires more sensitive and effective cancer detection methods. Fluorescence imaging with small molecule fluorescent probes has shown great promise for cancer detection but most of the developed probes lack active tumor cell targeting, which makes them unable to selectively target tumors, thereby reducing the accuracy of in vivo tumor detection. Herein, we report a novel probe Bio-S that combines a viscosity-sensitive and cell membrane targetable fluorescent group with biotin for targeted imaging and precise visualization of tumor cells and tumors. Bio-S exhibits sensitive fluorescence changes for viscosity at ∼660 nm and excellent cell membrane localization and imaging ability (red fluorescence, wash-free, and long-term imaging). Moreover, compared with the nonbiotinylated control probe C6-S, the biotinylated Bio-S can specifically target tumor cell membranes, thereby achieving much higher selectivity and sensitivity in distinguishing tumor cells from normal cells. Mice imaging experiments show that tail vein injection of Bio-S can target tumors and monitor lung cancer metastasis at the in vivo level. Therefore, this work provides an effective new strategy and tool for tumor-targeted detection and precise diagnosis.

Enhancing Molecular-Level Biological Monitoring with a Smart Self-Assembling 19F-Labeled Probe

Real-time monitoring of molecular transformations is crucial for advancements in biotechnology. In this study, we introduce a novel self-assembling 19F-labeled nuclear magnetic resonance (NMR) probe that disassembles upon interaction with various nucleotides. This interaction not only activates the 19F signals but also produces distinct signatures for each specific component, thereby enabling precise identification and quantification of molecules in evolving samples. We demonstrate the capability of this probe for real-time monitoring of adenosine triphosphate (ATP) hydrolysis and screening potential enzyme inhibitors. These applications highlight the probe's significant potential in enzyme analysis, drug development, and disease diagnostics.

Rational Design of an Activatable Near-Infrared Fluorogenic Platform for In Vivo Orthotopic Tumor Imaging and Resection

Rational and effective design of a universal near-infrared (NIR) light-absorbed platform employed to prepare diverse activatable NIR fluorogenic probes for in vivo imaging and the imaging-guided tumor resection remains less exploited but highly meaningful. Herein, mandelic acid with a core structure of 4-hydroxylbenzyl alcohol to link recognition unit, a fluorophore and a quencher was employed to prepare activatable probes. We exemplified ester as carboxylesterase (CE)-recognized unit, ferrocene as quencher and phenothiazinium as NIR fluorophore to afford fluorogenic probes termed NBS-Fe-CE and NBS-C-Fe-CE. These probes enabled the conversion toward CE with significant fluorescence increases and successfully discriminate CE activity in cells. NIR light enhances the tumor penetration and enable imaging-guided orthotopic tumor resection. This specific case demonstrated that this platform can be effectively used to construct diverse NIR probes for imaging analytes in biological systems.

Advances in Organic Fluorescent and Colorimetric Probes for The Detection of Cu2+ and Their Applications in Cancer Cell Imaging (2020-2024)

Organic fluorescence and colorimetric probes have emerged as vital tools for detecting metal ions, due to their high sensitivity, selectivity, and rapid response times. Copper, an essential trace element, plays a critical role in biological systems, yet its imbalance can lead to severe disorders such as neurodegenerative diseases, cancer, and Wilson's disease. Over the past few years, advancements in probe design have unlocked innovative avenues for not only detecting Cu2+ in environmental and biological samples but also for visualizing its distribution through fluorescence imaging. These probes offering robust performance under diverse conditions. Fluorescence imaging using these probes plays a pivotal role in cancer diagnosis, prognosis, and treatment monitoring by offering real-time visualization of tumor morphology and biomolecular interactions at cellular and tissue levels. This review aims to explore the diversity of organic fluorescence and colorimetric probes developed for the detection of Cu2+, with a particular focus on their applications in fluorescence imaging from 2020 to 2024. The discussion highlights the use of these probes in visualizing Cu2+ in various cancer cells such as SiHa, HCT 116, GES-1, RAW 264.7, HepG2, HeLa, MCF-7 and DrG cell lines, tissues, and small living organisms. By targeting cancer-specific pathways and monitoring copper-related physiological changes, these probes have significantly advanced the fields of cancer diagnostics and therapeutics. This comprehensive analysis emphasizes the potential of fluorescence imaging as a powerful tool for elucidating the roles of Cu2+ in health and disease, paving the way for future advances in biomedical research.

Recent progress towards the development of fluorescent probes for the detection of disease-related enzymes

Normal physiological functions as well as regulatory mechanisms for various pathological conditions depend on the activity of enzymes. Thus, determining the in vivo activity of enzymes is crucial for monitoring the physiological metabolism and diagnosis of diseases. Traditional enzyme detection methods are inefficient for in vivo detection, which have different limitations, such as high cost, laborious, and inevitable invasive procedures, low spatio-temporal resolution, weak anti-interference ability, and restricted scope of application. Because of its non-destructive nature, ultra-environmental sensitivity, and high spatiotemporal resolution, fluorescence imaging technology has emerged as a potent tool for the real-time visualization of live cells, thereby imaging the motility of proteins and intracellular signalling networks in tissues and cells and evaluating the binding and attraction of molecules. In the last few years, significant advancements have been achieved in detecting and imaging enzymes in biological systems. In this regard, the high sensitivity and unparalleled spatiotemporal resolution of fluorescent probes in association with confocal microscopy have garnered significant interest. In this review, we focus on providing a concise summary of the latest developments in the design of fluorogenic probes used for monitoring disease-associated enzymes and their application in biological imaging. We anticipate that this study will attract considerable attention among researchers in the relevant field, encouraging them to pursue advances in the development and application of fluorescent probes for the real-time monitoring of enzyme activity in live cells and in vivo models while ensuring excellent biocompatibility.

An activatable near-infrared fluorescent probe with large Stokes shift for visualizing peroxynitrite in Alzheimer's disease models

Alzheimer's disease (AD), characterized by its incurable nature and prevalence among the elderly, has remained a focal point in medical research. Increasing evidence suggests that peroxynitrite (ONOO-) serves as a crucial biomarker for the diagnosis of AD. In this study, we present a novel, easily available, high-yield, and cost-effective near-infrared (NIR) fluorescent probe, CDCI-ONOO. This probe utilizes a coumarin-dicyanoisophorone conjugate as the fluorophore and diphenylphosphinic chloride as the recognition site, enabling the detection of ONOO- both in vitro and in vivo. Upon interaction with ONOO-, CDCI-ONOO exhibits a distinct maximum emission peak at 715 nm with a substantial Stokes shift of 184 nm. The probe demonstrates excellent selectivity and sensitivity (LOD = 144 nM), along with noticeable colorimetric and fluorescence changes after the reaction. Comprehensive analyses using high-performance liquid chromatography (HPLC), high-resolution mass spectrometry (HRMS), and density functional theory (DFT) calculations confirm that the reaction with ONOO- restores the initially quenched Intramolecular Charge Transfer (ICT), resulting in the formation of CDCI-OH, a product that emitting fluorescence in the near-infrared region. Furthermore, we demonstrated the successful application of CDCI-ONOO for ONOO- detection in neuronal cells and imaging of ONOO- in the brains of mice. These findings underscore the potential of CDCI-ONOO as a near-infrared fluorescent probe for in vivo ONOO- detection, offering a significant avenue for advancing our understanding of AD pathology and diagnosis.

Mitochondria-Targeted DNA-Based Nanoprobe for In Situ Monitoring of the Activity of the mtDNA Repair Enzyme and Evaluating Tumor Radiosensitivity

Evaluating tumor radiosensitivity is beneficial for the prediction of treatment efficacy, customization of treatment plans, and minimization of side effects. Tracking the mitochondrial DNA (mtDNA) repair process helps to assess tumor radiosensitivity as mtDNA repair determines the fate of the cell under radiation-induced mtDNA damage. However, current probes developed to monitor levels of DNA repair enzymes suffered from complex synthesis, uncontrollable preparation, limited tumor selectivity, and poor organelle-targeting ability. Especially, the correlation between mtDNA repair activity and inherent radiosensitivity of tumors has not yet been explored. Here, we present a mitochondria-targeted DNA-based nanoprobe (TPP-Apt-tFNA) for in situ monitoring of the activity of the mtDNA repair enzyme and evaluating tumor radiosensitivity. TPP-Apt-tFNA consists of a DNA tetrahedral framework precisely modified with three functional modules on each of the three vertexes, that is, the tumor cell-targeting aptamer, the mitochondrion-targeting moiety, and the apurinic/apyrimidinic endonuclease 1 (APE1)-responsive molecule beacon. Once selectively internalized by tumor cells, the nanoprobe targeted the mitochondrion and specifically recognized APE1 to activate fluorescence, allowing the observation of mtDNA repair activity. The nanoprobe showed elevated APE1 levels in the mitochondria of tumor cells under oxidative stress. Moreover, the nanoprobe enabled the illumination of different levels of APE1-mediated mtDNA repair activity in different cell cycle phases. Furthermore, using the nanoprobe in vitro and in vivo, we found that tumor cells with high activity of mtDNA repair, which allowed them to recover from radiation-induced mtDNA lesions, had low sensitivity to radiation and an unsatisfactory radiotherapy outcome. Our work provides a new imaging tool for exploring the roles of mtDNA repair activity in diverse biological processes and for guiding tumor radiation treatment.

Synthesis, characterization, and computational evaluation of some synthesized xanthone derivatives: focus on kinase target network and biomedical properties

Background

Xanthones are dubbed as putative lead-like molecules for cancer drug design and discovery. This study was aimed at the synthesis, characterization, and in silico target fishing of novel xanthone derivatives.

Methods

The products of reactions of xanthydrol with urea, thiourea, and thiosemicarbazide reacted with α-haloketones to prepare the thiazolone compounds. Xanthydrol reacted sequentially with ethyl chloroacetate, hydrazine, carbon disulfide, and α-haloketones to prepare the dithiolane. The xanthydrol reacted with propargyl bromide and it submitted to click reaction with azide to prepare triazole ring.

Results

Finally, four novel xanthones derivatives including (E)-2-(2-(9H-xanthen-9-yl)hydrazono)-1,3-dithiolan-4-one (L3), 2-(2-(9H-xanthen-9-yl)hydrazinyl)thiazol-5(4H)-one (L5), 2-(9H-xanthen-9-ylamino)thiazol-5(4H)-one (L7), and 4-((9H-xanthen-9-yloxy)methyl)-1-(4-nitrophenyl)-1H-1,2,3-triazole (L9) were synthesized and characterized using thin layer chromatography, Fourier-transform infrared spectroscopy, and nuclear magnetic resonance (1H and 13C). ADMET, Pfizer filter, adverse drug reaction, toxicity, antitarget interaction profiles, target fishing, kinase target screening, molecular docking validation, and protein and gene network analysis were computed for derivatives. Ligands obeyed Pfizer filter for drug-likeness, while all ligands were categorized as toxic chemicals. Major targets of all ligands were predicted to be kinases including Haspin, WEE2, and PIM3. Mitogen-activated protein kinase 1 was the hub gene of target kinase network of all derivatives. All the ligands were predicted to show hepatotoxic potentials, while L7 presented cardiac toxicity.

Conclusion

Acute leukemic T-cells were one of the top predicted tumor cell lines for these ligands. The possible antileukemic effects of synthesized xanthone derivatives are potentially very interesting and warrant further studies.

Covalent assembly-based two-photon fluorescent probes for in situ visualizing nitroreductase activities: From cancer cells to human cancer tissues

Nitroreductase (NTR) is widely regarded as a biomarker whose enzymatic activity correlates with the degree of hypoxia in solid malignant tumors. Herein, we utilized 2-dimethylamino-7-hydroxynaphthalene as fluorophore linked diverse nitroaromatic groups to obtain four NTR-activatable two-photon fluorescent probes based on covalent assembly strategy. With the help of computer docking simulation and in vitro assay, the sulfonate-based probe XN3 was proved to be able to identify NTR activity with best performances in rapid response, outstanding specificity, and sensitivity in comparison with the other three probes. Furthermore, XN3 could detect the degree of hypoxia by monitoring NTR activity in kinds of cancer cells with remarkable signal-to-noise ratios. In cancer tissue sections of the breast and liver in mice, XN3 had the ability to differentiate between healthy and tumorous tissues, and possessed excellent fluorescence stability, high tissue penetration and low tissue autofluorescence. Finally, XN3 was successfully utilized for in situ visualizing NTR activities in human transverse colon and rectal cancer tissues, respectively. The findings suggested that XN3 could directly identify the boundary between cancer and normal tissues by monitoring NTR activities, which provides a new method for imaging diagnosis and intraoperative navigation of tumor tissue.

Raman Imaging of Targeted Drug Delivery with DNA-Based Nano-Optical Devices

Raman spectroscopy (RS) has emerged as a novel optical imaging modality by identifying molecular species through their bond vibrations, offering high specificity and sensitivity in molecule detection. However, its application in intracellular molecular probing has been limited due to challenges in combining vibrational tags with functional probes. DNA nanostructures, known for their high programmability, have been instrumental in fields like biomedicine and nanofabrication. So far, their ability to customize Raman signals remains largely untapped. In this study, a new class of Raman active DNA origami-based hybrid nanodevice (ND) for targeted cancer cell drug delivery and imaging is engineered. The ND is specifically engineered for metastatic prostate cancer treatment, featuring a legumain enzyme-responsive sequence for the controlled release of the chemotherapeutic agent doxorubicin. Integrating RS with precise targeting, the ND enables imaging of aggressive cancer cells and efficient drug delivery with minimal off-target effects. The developed device offers stimuli-responsive behavior, enhanced stability, exceptional tunability, and potent targeting abilities, positioning it as a highly promising strategy for advancing precision cancer imaging and therapy.

Fluorogenic Labeling Probe for the Imaging of Endogenous β-Galactosidase Activity in Cancer and Senescent Cells

The sensitive detection of glycosidases in live cells is crucial to understanding their functional roles in disease progression. Here, we develop a fluorogenic labeling probe for β-galactosidase (β-Gal) based on a bright green-emitting fluorescent dye, fluorescein. Galactose was introduced to a fluoromethyl-substituted fluorescein derivative through a benzyl spacer, resulting in a quenched fluorescence due to spirocyclization of the dye. After removal of the galactosyl residue by β-Gal, an ∼210-fold enhanced green fluorescence (emission maximum at 524 nm) was detected, and the presence of other glycosidases and hydrolases did not produce false-positive signals. The probe was successfully used for imaging of the endogenous β-Gal activity in cancer and senescent cells, and the imaging results agree with the β-Gal expression level of the cells, as determined by Western blotting and polymerase chain reaction. Importantly, we demonstrated that upon hydrolysis of galactose, the fluoromethyl-substituted fluorescein derivative is covalently attached to adjacent proteins, both in solution and in live cells. This study offers a small-molecule probe for the sensitive monitoring of endogenous glycosidase activity.

Illuminating cisplatin-induced ferroptosis in non-small-cell lung cancer with biothiol-activatable fluorescent/photoacoustic bimodal probes

Ferroptosis modulation represents a pioneering therapeutic approach for non-small-cell lung cancer (NSCLC), where precise monitoring and regulation of ferroptosis levels are pivotal for achieving optimal therapeutic outcomes. Cisplatin (Cis), a widely used chemotherapy drug for NSCLC, demonstrates remarkable therapeutic efficacy, potentially through its ability to induce ferroptosis and synergize with other treatments. However, in vivo studies of ferroptosis face challenges due to the scarcity of validated biomarkers and the absence of reliable tools for real-time visualization. Biothiols emerge as suitable biomarkers for ferroptosis, as their concentrations decrease significantly during this process. To address these challenges, fluorescence/photoacoustic (PA) bimodal imaging offers a promising solution by providing more accurate in vivo information on ferroptosis. Therefore, the development of methods to detect biothiols using fluorescence/PA bimodal imaging is highly desirable for visualizing ferroptosis in NSCLC. In this study, we designed and constructed two activatable near-infrared (NIR) fluorescent/PA bimodal imaging probes specifically for visualizing ferroptosis by monitoring the fluctuations in biothiol levels. These probes exhibited excellent bimodal response performance in solution, cells, and tumors. Furthermore, they were successfully applied for real-time monitoring of biothiol changes during the ferroptosis process in NSCLC cells and tumors. Importantly, our findings revealed that the combined use of erastin and cisplatin exacerbates the consumption of biothiols, suggesting an enhancement of ferroptosis in NSCLC. This work not only provides powerful tools for monitoring in vivo ferroptosis but also facilitates the study of ferroptosis mechanisms and holds the potential to further advance the treatment of NSCLC.

An estrogen receptor β-targeted near-infrared probe for theranostic imaging of prostate cancer

Estrogen receptor β (ERβ) is aberrantly expressed in castration-resistant prostate cancer (CRPC). Therefore, a diagnostic and therapeutic ERβ probe not only helps to reveal the complex role of ERβ in prostate cancer (PCa), but also promotes ERβ-targeted PCa therapy. Herein, we reported a novel ERβ-targeted near-infrared fluorescent probe D3 with both imaging and therapeutic functions, which had the advantages of high ERβ selectivity, good optical performance, and strong anti-interference ability. In addition, it displayed excellent antiproliferative activity in CRPC cells. Finally, D3 was also successfully applied to the in vivo imaging of ERβ in the prostate cancer mouse model. Thus, this ERβ-targeted near-infrared fluorescent probe can be used as a potential tool for the study of ERβ-targeted diagnostic and therapeutic PCa.

Diaminonaphthalene Boronic Acid (DANBA): New Approach for Peroxynitrite Sensing Site

Selective detection of reactive oxygen species (ROS) is vital for studying their role in brain diseases. Fluorescence probes can distinguish ONOO- species from other ROS; however, their selectivity toward ONOO- species depends on the ONOO- recognition group. Aryl-boronic acids and esters, which are common ONOO- recognition groups, are not selective for ONOO- over H2O2. In this study, we developed a diaminonaphthalene (DAN)-protected boronic acid as a new ONOO- recognition group that selectively reacts with ONOO- over H2O2 and other ROS. Three DAN-protected boronic acid (DANBA)-based fluorophores that emit fluorescence over visible to near-infrared (NIR) regions, Cou-BN, BVP-BN, and HDM-BN, and their aryl-boronic acid-based counterparts (Cou-BO, BVP-BO, and HDM-BO), were developed. The DANBA-based probes exhibited enhanced selectivity toward ONOO- over that of their control group, as well as universality in solution assays and in vitro experiments with PC12 cells. The NIR-emissive HDM-BN was optimized to delineate in vivo ONOO- levels in mouse brains with Parkinson's disease. This DAN-protected boronic acid belongs to a new generation of recognition groups for developing ONOO- probes, and this strategy could be extended to other common hydroxyl-containing dyes to detect ONOO- levels in complex biological systems and processes.

Pretheranostic agents with extraordinaryNIRF/photoacoustic imaging performanceand photothermal oncotherapy efficacy

Cervical cancer, the most common gynecological malignancy, significantly and adversely affects women's physical health and well-being. Traditional surgical interventions and chemotherapy, while potentially effective, often entail serious side effects that have led to an urgent need for novel therapeutic methods. Photothermal therapy (PTT) has emerged as a promising approach due to its ability to minimize damage to healthy tissue. Connecting a biothiol detection group to PTT-sensitive molecules can improve tumor targeting and further minimize potential side effects. In this study, we developed a near-infrared fluorescence (NIRF)/photoacoustic (PA) dual-mode probe, S-NBD, which demonstrated robust PTT performance. This innovative probe is capable of activating NIRF/PA signals to enable the detection of biothiols with high emission wavelength (838 nm) and large Stokes shift (178 nm), allowing for in vivo monitoring of cancer cells. Additionally, the probe achieved an outstanding photothermal conversion efficiency of 67.1%. The application of laser irradiation (660 nm, 1.0 W/cm2, 5 min) was able to achieve complete tumor ablation without recurrence. In summary, this seminal study presents a pioneering NIRF/PA dual-mode dicyanoisophorone-based probe for biothiol imaging, incorporating features from PTT for the first time. This pioneering approach achieves the dual objectives of improving tumor diagnosis and treatment.

Magnetic-susceptibility-dependent ratiometric probes for enhancing quantitative MRI

In magnetic resonance imaging (MRI), quantitative measurements of analytes are hindered by difficulties in distinguishing the MRI signals of activation of the probe by the analyte from those of the accumulation of the intact probe. Here we show that imaging sensitivity and quantitation can be enhanced by ratiometric MRI probes with a high relaxivity-ratio change (more than 2.5-fold at 7 T) via magnetic-susceptibility-dependent magnetic resonance tuning. Specifically, polymeric probes that incorporate paramagnetic Mn-porphyrin and superparamagnetic iron oxide nanoparticles inducing opposite changes in the longitudinal and transverse magnetic relaxivities responded to analyte concentration independently of probe concentration. In mice, the probes allowed for quantitative real-time dynamic imaging of H2O2, H2S or pH in subcutaneous tumours, in livers with drug-induced injury and in orthotropic gliomas. The ratiometric MRI probes may be advantageously used to obtain molecular insight into pathological processes and to circumvent interference from dynamic changes in probe concentration within the body while providing anatomical information.

Reactive oxygen species-mediated organic long-persistent luminophores light up biomedicine: from two-component separated nano-systems to integrated uni-luminophores

Organic luminophores have been widely utilized in cells and in vivo fluorescence imaging but face extreme challenges, including a low signal-to-noise ratio (SNR) and even false signals, due to non-negligible background signals derived from real-time excitation lasers. To overcome these challenges, in the last decade, functionalized organic long-persistent luminophores have gained much attention. Such luminophores could not only overcome the biological toxicity of inorganic long-persistent luminescent materials (metabolic toxicity and leakage risk of inorganic heavy metals), but also continue to emit long-persistent luminescence after removing the excitation source, thus effectively improving imaging quality. More importantly, organic long-persistent luminophores have good structure tailorability for the construction of activable probes, which is favorable for biosensing. Recently, the development of reactive oxygen species (ROS)-mediated long-persistent (ROSLP) luminophores (especially organic small-molecule ROSLP luminophores) is still in the rising stage. Notably, ROSLP luminophores for in vivo imaging have experienced from two-component separated nano-systems to integrated uni-luminophores, which obtained gradually better designability and biocompatibility. In this review, we summarize the progress and challenges of organic long-persistent luminophores, focusing on their development history, long-persistent luminescence working mechanisms, and biomedical applications. We hope that these insights will help scientists further develop functionalized organic long-persistent luminophores for the biomedical field.

Multicomponent Diversity-Oriented Access to Boronic-Acid-Derived Pyrrolide Salicyl-Hydrazone Fluorophores with Strong Solid-State Emission

Fluorescent molecular platforms are highly sought after for their applications in biology and optoelectronics but face challenges with solid-state emission quenching. To address this, bulky substituents or aggregation-induced emission luminogens to restrict intramolecular motion are used to enhance the brightness. Here, we have successfully engineered a novel class of boron complexed pyrrolide salicyl-hydrazone fluorophores named BPSHY. These dyes were synthesized through a diversity-oriented condensation of pyrrole and salicylaldehyde derivatives combined with various aromatic boronic acids. The resulting 3D structures, owing to bulky boron axially substituted aryl groups, impart excellent solubility in a variety of solvents. Significantly, the BPSHY dyes exhibit strong absorption in the visible region and remarkably large Stokes shifts. Crucially, they demonstrate intense emission in aqueous solutions due to aggregation-induced emission effects. In solid-states, these dyes achieve high quantum yields, reaching up to 58%. Further expanding their utility, we developed two new BPSHY probes: one incorporating morpholine and another containing triphenylphosphine salt. Both of them are found to specifically label subcellular organelles such as lysosomes and mitochondria within live cells. Notably, these probes demonstrate exceptional staining efficacy and two-photon fluorescence feature. This highlights the considerable promise of BPSHY fluorophores for monitoring and visualizing the dynamic transformations of organelles.

Nanoscale Metal-Organic Frameworks as a Photoluminescent Platform for Bioimaging and Biosensing Applications

The tracking of nanomedicines in their concentration and location inside living systems has a pivotal effect on the understanding of the biological processes, early-stage diagnosis, and therapeutic monitoring of diseases. Nanoscale metal-organic frameworks (nano MOFs) possess high surface areas, definite structure, regulated optical properties, rich functionalized sites, and good biocompatibility that allow them to excel in a wide range of biomedical applications. Controllable syntheses and functionalization endow nano MOFs with better properties as imaging agents and sensing units for the diagnosis and treatment of diseases. This minireview summarizes the tunable synthesis strategies of nano MOFs with controllable size, shape, and regulated luminescent performance, and pinpoints their recent advanced applications as optical elements in bioimaging and biosensing. The current limitations and future development directions of nano MOF-contained materials in bioimaging and biosensing applications are also discussed, aiming to expand the biological applications of nano MOF-based nanomedicine and facilitate their production or clinical translation.

Leveraging the Photofunctions of Transition Metal Complexes for the Design of Innovative Phototherapeutics

Despite the advent of various medical interventions for cancer treatment, the disease continues to pose a formidable global health challenge, necessitating the development of new therapeutic approaches for more effective treatment outcomes. Photodynamic therapy (PDT), which utilizes light to activate a photosensitizer to produce cytotoxic reactive oxygen species (ROS) for eradicating cancer cells, has emerged as a promising approach for cancer treatment due to its high spatiotemporal precision and minimal invasiveness. However, the widespread clinical use of PDT faces several challenges, including the inefficient production of ROS in the hypoxic tumor microenvironment, the limited penetration depth of light in biological tissues, and the inadequate accumulation of photosensitizers at the tumor site. Over the past decade, there has been increasing interest in the utilization of photofunctional transition metal complexes as photosensitizers for PDT applications due to their intriguing photophysical and photochemical properties. This review provides an overview of the current design strategies used in the development of transition metal complexes as innovative phototherapeutics, aiming to address the limitations associated with PDT and achieve more effective treatment outcomes. The current challenges and future perspectives on the clinical translation of transition metal complexes are also discussed.